/* bc.c - An implementation of POSIX bc.
 *
 * Copyright 2018 Gavin D. Howard <yzena.tech@gmail.com>
 *
 * See http://pubs.opengroup.org/onlinepubs/9699919799/utilities/bc.html

USE_BC(NEWTOY(bc, "i(interactive)l(mathlib)q(quiet)s(standard)w(warn)", TOYFLAG_USR|TOYFLAG_BIN|TOYFLAG_LOCALE))

config BC
  bool "bc"
  default n
  help
    usage: bc [-ilqsw] [file ...]

    bc is a command-line calculator with a Turing-complete language.

    options:

      -i  --interactive  force interactive mode
      -l  --mathlib      use predefined math routines:

                         s(expr)  =  sine of expr in radians
                         c(expr)  =  cosine of expr in radians
                         a(expr)  =  arctangent of expr, returning radians
                         l(expr)  =  natural log of expr
                         e(expr)  =  raises e to the power of expr
                         j(n, x)  =  Bessel function of integer order n of x

      -q  --quiet        don't print version and copyright
      -s  --standard     error if any non-POSIX extensions are used
      -w  --warn         warn if any non-POSIX extensions are used

*/

#define FOR_bc
#include "toys.h"

GLOBALS(
  // This actually needs to be a BcVm*, but the toybox build
  // system complains if I make it so. Instead, we'll just cast.
  char *vm;
)

#define BC_VM ((BcVm*) TT.vm)

typedef enum BcStatus {

  BC_STATUS_SUCCESS = 0,
  BC_STATUS_ERROR,
  BC_STATUS_EOF,
  BC_STATUS_EMPTY_EXPR,
  BC_STATUS_SIGNAL,
  BC_STATUS_QUIT,

} BcStatus;

typedef enum BcError {

  BC_ERROR_VM_ALLOC_ERR,
  BC_ERROR_VM_IO_ERR,
  BC_ERROR_VM_BIN_FILE,
  BC_ERROR_VM_PATH_DIR,

  BC_ERROR_PARSE_EOF,
  BC_ERROR_PARSE_CHAR,
  BC_ERROR_PARSE_STRING,
  BC_ERROR_PARSE_COMMENT,
  BC_ERROR_PARSE_TOKEN,
  BC_ERROR_EXEC_NUM_LEN,
  BC_ERROR_EXEC_NAME_LEN,
  BC_ERROR_EXEC_STRING_LEN,
  BC_ERROR_PARSE_EXPR,
  BC_ERROR_PARSE_EMPTY_EXPR,
  BC_ERROR_PARSE_PRINT,
  BC_ERROR_PARSE_FUNC,
  BC_ERROR_PARSE_ASSIGN,
  BC_ERROR_PARSE_NO_AUTO,
  BC_ERROR_PARSE_DUP_LOCAL,
  BC_ERROR_PARSE_BLOCK,
  BC_ERROR_PARSE_RET_VOID,

  BC_ERROR_MATH_NEGATIVE,
  BC_ERROR_MATH_NON_INTEGER,
  BC_ERROR_MATH_OVERFLOW,
  BC_ERROR_MATH_DIVIDE_BY_ZERO,

  BC_ERROR_EXEC_FILE_ERR,
  BC_ERROR_EXEC_ARRAY_LEN,
  BC_ERROR_EXEC_IBASE,
  BC_ERROR_EXEC_OBASE,
  BC_ERROR_EXEC_SCALE,
  BC_ERROR_EXEC_READ_EXPR,
  BC_ERROR_EXEC_REC_READ,
  BC_ERROR_EXEC_TYPE,
  BC_ERROR_EXEC_PARAMS,
  BC_ERROR_EXEC_UNDEF_FUNC,
  BC_ERROR_EXEC_VOID_VAL,

  BC_ERROR_POSIX_START,

  BC_ERROR_POSIX_NAME_LEN = BC_ERROR_POSIX_START,
  BC_ERROR_POSIX_COMMENT,
  BC_ERROR_POSIX_KW,
  BC_ERROR_POSIX_DOT,
  BC_ERROR_POSIX_RET,
  BC_ERROR_POSIX_BOOL,
  BC_ERROR_POSIX_REL_POS,
  BC_ERROR_POSIX_MULTIREL,
  BC_ERROR_POSIX_FOR1,
  BC_ERROR_POSIX_FOR2,
  BC_ERROR_POSIX_FOR3,
  BC_ERROR_POSIX_BRACE,
  BC_ERROR_POSIX_REF,

} BcError;

#define BC_ERR_IDX_VM (0)
#define BC_ERR_IDX_PARSE (1)
#define BC_ERR_IDX_MATH (2)
#define BC_ERR_IDX_EXEC (3)
#define BC_ERR_IDX_POSIX (4)

#define BC_UNUSED(e) ((void) (e))

#define BC_VEC_START_CAP (1<<5)

typedef unsigned char uchar;

typedef void (*BcVecFree)(void*);

// Forward declaration.
struct BcId;

typedef struct BcVec {
  char *v;
  size_t len;
  size_t cap;
  size_t size;
  BcVecFree dtor;
} BcVec;

#define bc_vec_pop(v) (bc_vec_npop((v), 1))
#define bc_vec_top(v) (bc_vec_item_rev((v), 0))

#define bc_map_init(v) (bc_vec_init((v), sizeof(BcId), bc_id_free))

#define BC_READ_BIN_CHAR(c) (((c) < ' ' && !isspace((c))) || ((uchar) c) > '~')

typedef signed char BcDig;

typedef struct BcNum {
  BcDig *num;
  size_t rdx;
  size_t len;
  size_t cap;
  int neg;
} BcNum;

#define BC_NUM_MIN_BASE ((unsigned long) 2)
#define BC_NUM_MAX_POSIX_IBASE ((unsigned long) 16)
#define BC_NUM_MAX_IBASE ((unsigned long) 36)
// This is the max base allowed by bc_num_parseChar().
#define BC_NUM_MAX_LBASE ('Z' + 10 + 1)
#define BC_NUM_DEF_SIZE (16)
#define BC_NUM_PRINT_WIDTH (69)

#define BC_NUM_KARATSUBA_LEN (32)

// A crude, but always big enough, calculation of
// the size required for ibase and obase BcNum's.
#define BC_NUM_LONG_LOG10 ((CHAR_BIT * sizeof(unsigned long) + 1) / 2 + 1)

#define BC_NUM_NEG(n, neg) ((((ssize_t) (n)) ^ -((ssize_t) (neg))) + (neg))

#define BC_NUM_ONE(n) ((n)->len == 1 && (n)->rdx == 0 && (n)->num[0] == 1)
#define BC_NUM_INT(n) ((n)->len - (n)->rdx)
#define BC_NUM_CMP_ZERO(a) (BC_NUM_NEG((a)->len != 0, (a)->neg))
#define BC_NUM_PREQ(a, b) ((a)->len + (b)->len + 1)
#define BC_NUM_SHREQ(a) ((a)->len)

#define BC_NUM_NUM_LETTER(c) ((c) - 'A' + 10)

typedef BcStatus (*BcNumBinaryOp)(BcNum*, BcNum*, BcNum*, size_t);
typedef size_t (*BcNumBinaryOpReq)(BcNum*, BcNum*, size_t);
typedef void (*BcNumDigitOp)(size_t, size_t, int);

void bc_num_init(BcNum *n, size_t req);
void bc_num_setup(BcNum *n, BcDig *num, size_t cap);
void bc_num_expand(BcNum *n, size_t req);
void bc_num_copy(BcNum *d, BcNum *s);
void bc_num_createCopy(BcNum *d, BcNum *s);
void bc_num_createFromUlong(BcNum *n, unsigned long val);
void bc_num_free(void *num);

BcStatus bc_num_ulong(BcNum *n, unsigned long *result);
void bc_num_ulong2num(BcNum *n, unsigned long val);

BcStatus bc_num_add(BcNum *a, BcNum *b, BcNum *c, size_t scale);
BcStatus bc_num_sub(BcNum *a, BcNum *b, BcNum *c, size_t scale);
BcStatus bc_num_mul(BcNum *a, BcNum *b, BcNum *c, size_t scale);
BcStatus bc_num_div(BcNum *a, BcNum *b, BcNum *c, size_t scale);
BcStatus bc_num_mod(BcNum *a, BcNum *b, BcNum *c, size_t scale);
BcStatus bc_num_pow(BcNum *a, BcNum *b, BcNum *c, size_t scale);
BcStatus bc_num_sqrt(BcNum *a, BcNum *b, size_t scale);
BcStatus bc_num_divmod(BcNum *a, BcNum *b, BcNum *c, BcNum *d, size_t scale);

size_t bc_num_addReq(BcNum *a, BcNum *b, size_t scale);

size_t bc_num_mulReq(BcNum *a, BcNum *b, size_t scale);
size_t bc_num_powReq(BcNum *a, BcNum *b, size_t scale);

typedef enum BcInst {

  BC_INST_INC_POST = 0,
  BC_INST_DEC_POST,
  BC_INST_INC_PRE,
  BC_INST_DEC_PRE,

  BC_INST_NEG,
  BC_INST_BOOL_NOT,

  BC_INST_POWER,
  BC_INST_MULTIPLY,
  BC_INST_DIVIDE,
  BC_INST_MODULUS,
  BC_INST_PLUS,
  BC_INST_MINUS,

  BC_INST_REL_EQ,
  BC_INST_REL_LE,
  BC_INST_REL_GE,
  BC_INST_REL_NE,
  BC_INST_REL_LT,
  BC_INST_REL_GT,

  BC_INST_BOOL_OR,
  BC_INST_BOOL_AND,

  BC_INST_ASSIGN_POWER,
  BC_INST_ASSIGN_MULTIPLY,
  BC_INST_ASSIGN_DIVIDE,
  BC_INST_ASSIGN_MODULUS,
  BC_INST_ASSIGN_PLUS,
  BC_INST_ASSIGN_MINUS,
  BC_INST_ASSIGN,

  BC_INST_NUM,
  BC_INST_VAR,
  BC_INST_ARRAY_ELEM,
  BC_INST_ARRAY,

  BC_INST_LAST,
  BC_INST_IBASE,
  BC_INST_OBASE,
  BC_INST_SCALE,
  BC_INST_LENGTH,
  BC_INST_SCALE_FUNC,
  BC_INST_SQRT,
  BC_INST_ABS,
  BC_INST_READ,

  BC_INST_PRINT,
  BC_INST_PRINT_POP,
  BC_INST_STR,
  BC_INST_PRINT_STR,

  BC_INST_JUMP,
  BC_INST_JUMP_ZERO,

  BC_INST_CALL,

  BC_INST_RET,
  BC_INST_RET0,
  BC_INST_RET_VOID,

  BC_INST_HALT,

  BC_INST_POP,
  BC_INST_POP_EXEC,

} BcInst;

typedef struct BcId {
  char *name;
  size_t idx;
} BcId;

typedef struct BcFunc {

  BcVec code;
  BcVec labels;
  BcVec autos;
  size_t nparams;

  BcVec strs;
  BcVec consts;

  char *name;
  int voidfn;

} BcFunc;

typedef enum BcResultType {

  BC_RESULT_VAR,
  BC_RESULT_ARRAY_ELEM,
  BC_RESULT_ARRAY,

  BC_RESULT_STR,

  BC_RESULT_CONSTANT,
  BC_RESULT_TEMP,

  BC_RESULT_VOID,
  BC_RESULT_ONE,
  BC_RESULT_LAST,
  BC_RESULT_IBASE,
  BC_RESULT_OBASE,
  BC_RESULT_SCALE,

} BcResultType;

typedef union BcResultData {
  BcNum n;
  BcVec v;
  BcId id;
} BcResultData;

typedef struct BcResult {
  BcResultType t;
  BcResultData d;
} BcResult;

typedef struct BcInstPtr {
  size_t func;
  size_t idx;
  size_t len;
} BcInstPtr;

typedef enum BcType {
  BC_TYPE_VAR,
  BC_TYPE_ARRAY,
} BcType;

void bc_array_expand(BcVec *a, size_t len);
int bc_id_cmp(BcId *e1, BcId *e2);

#define bc_lex_err(l, e) (bc_vm_error((e), (l)->line))
#define bc_lex_verr(l, e, ...) (bc_vm_error((e), (l)->line, __VA_ARGS__))

#define BC_LEX_NUM_CHAR(c, l, pt) \
  (isdigit(c) || ((c) >= 'A' && (c) <= (l)) || ((c) == '.' && !(pt)))

// BC_LEX_NEG is not used in lexing; it is only for parsing.
typedef enum BcLexType {

  BC_LEX_EOF,
  BC_LEX_INVALID,

  BC_LEX_OP_INC,
  BC_LEX_OP_DEC,

  BC_LEX_NEG,
  BC_LEX_OP_BOOL_NOT,

  BC_LEX_OP_POWER,
  BC_LEX_OP_MULTIPLY,
  BC_LEX_OP_DIVIDE,
  BC_LEX_OP_MODULUS,
  BC_LEX_OP_PLUS,
  BC_LEX_OP_MINUS,

  BC_LEX_OP_REL_EQ,
  BC_LEX_OP_REL_LE,
  BC_LEX_OP_REL_GE,
  BC_LEX_OP_REL_NE,
  BC_LEX_OP_REL_LT,
  BC_LEX_OP_REL_GT,

  BC_LEX_OP_BOOL_OR,
  BC_LEX_OP_BOOL_AND,

  BC_LEX_OP_ASSIGN_POWER,
  BC_LEX_OP_ASSIGN_MULTIPLY,
  BC_LEX_OP_ASSIGN_DIVIDE,
  BC_LEX_OP_ASSIGN_MODULUS,
  BC_LEX_OP_ASSIGN_PLUS,
  BC_LEX_OP_ASSIGN_MINUS,
  BC_LEX_OP_ASSIGN,

  BC_LEX_NLINE,
  BC_LEX_WHITESPACE,

  BC_LEX_LPAREN,
  BC_LEX_RPAREN,

  BC_LEX_LBRACKET,
  BC_LEX_COMMA,
  BC_LEX_RBRACKET,

  BC_LEX_LBRACE,
  BC_LEX_SCOLON,
  BC_LEX_RBRACE,

  BC_LEX_STR,
  BC_LEX_NAME,
  BC_LEX_NUMBER,

  BC_LEX_KEY_AUTO,
  BC_LEX_KEY_BREAK,
  BC_LEX_KEY_CONTINUE,
  BC_LEX_KEY_DEFINE,
  BC_LEX_KEY_FOR,
  BC_LEX_KEY_IF,
  BC_LEX_KEY_LIMITS,
  BC_LEX_KEY_RETURN,
  BC_LEX_KEY_WHILE,
  BC_LEX_KEY_HALT,
  BC_LEX_KEY_LAST,
  BC_LEX_KEY_IBASE,
  BC_LEX_KEY_OBASE,
  BC_LEX_KEY_SCALE,
  BC_LEX_KEY_LENGTH,
  BC_LEX_KEY_PRINT,
  BC_LEX_KEY_SQRT,
  BC_LEX_KEY_ABS,
  BC_LEX_KEY_QUIT,
  BC_LEX_KEY_READ,
  BC_LEX_KEY_ELSE,

} BcLexType;

typedef struct BcLex {

  char *buf;
  size_t i;
  size_t line;
  size_t len;

  BcLexType t;
  BcLexType last;
  BcVec str;

} BcLex;

#define BC_PARSE_STREND ((uchar) UCHAR_MAX)

#define BC_PARSE_REL (1<<0)
#define BC_PARSE_PRINT (1<<1)
#define BC_PARSE_NOCALL (1<<2)
#define BC_PARSE_NOREAD (1<<3)
#define BC_PARSE_ARRAY (1<<4)

#define bc_parse_push(p, i) (bc_vec_pushByte(&(p)->func->code, (uchar) (i)))
#define bc_parse_number(p)(bc_parse_addId((p), BC_INST_NUM))
#define bc_parse_string(p)(bc_parse_addId((p), BC_INST_STR))

#define bc_parse_err(p, e) (bc_vm_error((e), (p)->l.line))
#define bc_parse_verr(p, e, ...) (bc_vm_error((e), (p)->l.line, __VA_ARGS__))

typedef struct BcParseNext {
  uchar len;
  uchar tokens[4];
} BcParseNext;

#define BC_PARSE_NEXT_TOKENS(...) .tokens = { __VA_ARGS__ }
#define BC_PARSE_NEXT(a, ...) \
  { .len = (uchar) (a), BC_PARSE_NEXT_TOKENS(__VA_ARGS__) }

struct BcProgram;

typedef struct BcParse {

  BcLex l;

  BcVec flags;
  BcVec exits;
  BcVec conds;
  BcVec ops;

  struct BcProgram *prog;
  BcFunc *func;
  size_t fidx;

  int auto_part;

} BcParse;

typedef struct BcLexKeyword {
  uchar data;
  char name[9];
} BcLexKeyword;

#define BC_LEX_CHAR_MSB(bit) ((bit) << (CHAR_BIT - 1))

#define BC_LEX_KW_POSIX(kw) ((kw)->data & (BC_LEX_CHAR_MSB(1)))
#define BC_LEX_KW_LEN(kw) ((size_t) ((kw)->data & ~(BC_LEX_CHAR_MSB(1))))

#define BC_LEX_KW_ENTRY(a, b, c) \
  { .data = ((b) & ~(BC_LEX_CHAR_MSB(1))) | BC_LEX_CHAR_MSB(c),.name = a }

#define bc_lex_posixErr(l, e) (bc_vm_posixError((e), (l)->line))
#define bc_lex_vposixErr(l, e, ...) \
  (bc_vm_posixError((e), (l)->line, __VA_ARGS__))

BcStatus bc_lex_token(BcLex *l);

#define BC_PARSE_TOP_FLAG_PTR(p) ((uint16_t*) bc_vec_top(&(p)->flags))
#define BC_PARSE_TOP_FLAG(p) (*(BC_PARSE_TOP_FLAG_PTR(p)))

#define BC_PARSE_FLAG_BRACE (1<<0)
#define BC_PARSE_BRACE(p) (BC_PARSE_TOP_FLAG(p) & BC_PARSE_FLAG_BRACE)

#define BC_PARSE_FLAG_FUNC_INNER (1<<1)
#define BC_PARSE_FUNC_INNER(p) (BC_PARSE_TOP_FLAG(p) & BC_PARSE_FLAG_FUNC_INNER)

#define BC_PARSE_FLAG_FUNC (1<<2)
#define BC_PARSE_FUNC(p) (BC_PARSE_TOP_FLAG(p) & BC_PARSE_FLAG_FUNC)

#define BC_PARSE_FLAG_BODY (1<<3)
#define BC_PARSE_BODY(p) (BC_PARSE_TOP_FLAG(p) & BC_PARSE_FLAG_BODY)

#define BC_PARSE_FLAG_LOOP (1<<4)
#define BC_PARSE_LOOP(p) (BC_PARSE_TOP_FLAG(p) & BC_PARSE_FLAG_LOOP)

#define BC_PARSE_FLAG_LOOP_INNER (1<<5)
#define BC_PARSE_LOOP_INNER(p) (BC_PARSE_TOP_FLAG(p) & BC_PARSE_FLAG_LOOP_INNER)

#define BC_PARSE_FLAG_IF (1<<6)
#define BC_PARSE_IF(p) (BC_PARSE_TOP_FLAG(p) & BC_PARSE_FLAG_IF)

#define BC_PARSE_FLAG_ELSE (1<<7)
#define BC_PARSE_ELSE(p) (BC_PARSE_TOP_FLAG(p) & BC_PARSE_FLAG_ELSE)

#define BC_PARSE_FLAG_IF_END (1<<8)
#define BC_PARSE_IF_END(p) (BC_PARSE_TOP_FLAG(p) & BC_PARSE_FLAG_IF_END)

#define BC_PARSE_NO_EXEC(p) ((p)->flags.len != 1 || BC_PARSE_TOP_FLAG(p) != 0)

#define BC_PARSE_DELIMITER(t) \
  ((t) == BC_LEX_SCOLON || (t) == BC_LEX_NLINE || (t) == BC_LEX_EOF)

#define BC_PARSE_BLOCK_STMT(f) \
  ((f) & (BC_PARSE_FLAG_ELSE | BC_PARSE_FLAG_LOOP_INNER))

#define BC_PARSE_OP(p, l) (((p) & ~(BC_LEX_CHAR_MSB(1))) | (BC_LEX_CHAR_MSB(l)))

#define BC_PARSE_OP_DATA(t) bc_parse_ops[((t) - BC_LEX_OP_INC)]
#define BC_PARSE_OP_LEFT(op) (BC_PARSE_OP_DATA(op) & BC_LEX_CHAR_MSB(1))
#define BC_PARSE_OP_PREC(op) (BC_PARSE_OP_DATA(op) & ~(BC_LEX_CHAR_MSB(1)))

#define BC_PARSE_EXPR_ENTRY(e1, e2, e3, e4, e5, e6, e7, e8)  \
  (((e1) << 7) | ((e2) << 6) | ((e3) << 5) | ((e4) << 4) | \
   ((e5) << 3) | ((e6) << 2) | ((e7) << 1) | ((e8) << 0))

#define BC_PARSE_EXPR(i) \
  (bc_parse_exprs[(((i) & (uchar) ~(0x07)) >> 3)] & (1 << (7 - ((i) & 0x07))))

#define BC_PARSE_TOP_OP(p) (*((BcLexType*) bc_vec_top(&(p)->ops)))
#define BC_PARSE_LEAF(prev, bin_last, rparen) \
  (!(bin_last) && ((rparen) || bc_parse_inst_isLeaf(prev)))
#define BC_PARSE_INST_VAR(t) \
  ((t) >= BC_INST_VAR && (t) <= BC_INST_SCALE && (t) != BC_INST_ARRAY)

#define BC_PARSE_PREV_PREFIX(p) \
  ((p) >= BC_INST_INC_PRE && (p) <= BC_INST_BOOL_NOT)
#define BC_PARSE_OP_PREFIX(t) ((t) == BC_LEX_OP_BOOL_NOT || (t) == BC_LEX_NEG)

// We can calculate the conversion between tokens and exprs by subtracting the
// position of the first operator in the lex enum and adding the position of
// the first in the expr enum. Note: This only works for binary operators.
#define BC_PARSE_TOKEN_INST(t) ((uchar) ((t) - BC_LEX_NEG + BC_INST_NEG))

#define bc_parse_posixErr(p, e) (bc_vm_posixError((e), (p)->l.line))

BcStatus bc_parse_parse(BcParse *p);
BcStatus bc_parse_expr_status(BcParse *p, uint8_t flags, BcParseNext next);

#define BC_PROG_ONE_CAP (1)

typedef struct BcProgram {

  size_t scale;

  BcNum ib;
  size_t ib_t;
  BcNum ob;
  size_t ob_t;

  BcVec results;
  BcVec stack;

  BcVec fns;
  BcVec fn_map;

  BcVec vars;
  BcVec var_map;

  BcVec arrs;
  BcVec arr_map;

  BcNum one;
  BcNum last;

  BcDig ib_num[BC_NUM_LONG_LOG10];
  BcDig ob_num[BC_NUM_LONG_LOG10];
  BcDig one_num[BC_PROG_ONE_CAP];

} BcProgram;

#define BC_PROG_STACK(s, n) ((s)->len >= ((size_t) (n)))

#define BC_PROG_MAIN (0)
#define BC_PROG_READ (1)

#define BC_PROG_STR(n) (!(n)->num && !(n)->cap)
#define BC_PROG_NUM(r, n) \
  ((r)->t != BC_RESULT_ARRAY && (r)->t != BC_RESULT_STR && !BC_PROG_STR(n))

typedef void (*BcProgramUnary)(BcResult*, BcNum*);

void bc_program_addFunc(BcProgram *p, BcFunc *f, char *name);
size_t bc_program_insertFunc(BcProgram *p, char *name);
BcStatus bc_program_reset(BcProgram *p, BcStatus s);
BcStatus bc_program_exec(BcProgram *p);

unsigned long bc_program_scale(BcNum *n);
unsigned long bc_program_len(BcNum *n);

void bc_program_negate(BcResult *r, BcNum *n);
void bc_program_not(BcResult *r, BcNum *n);

#define BC_FLAG_TTYIN (1<<7)
#define BC_TTYIN (toys.optflags & BC_FLAG_TTYIN)

#define BC_S (toys.optflags & FLAG_s)
#define BC_W (toys.optflags & FLAG_w)
#define BC_L (toys.optflags & FLAG_l)
#define BC_I (toys.optflags & FLAG_i)

#define BC_MAX_OBASE ((unsigned long) INT_MAX)
#define BC_MAX_DIM ((unsigned long) INT_MAX)
#define BC_MAX_SCALE ((unsigned long) UINT_MAX)
#define BC_MAX_STRING ((unsigned long) UINT_MAX - 1)
#define BC_MAX_NAME BC_MAX_STRING
#define BC_MAX_NUM BC_MAX_STRING
#define BC_MAX_EXP ((unsigned long) ULONG_MAX)
#define BC_MAX_VARS ((unsigned long) SIZE_MAX - 1)

#define BC_SIGNAL (BC_VM->sig)
#define BC_SIGINT (BC_VM->sig == SIGINT)

#ifdef SIGQUIT
#define BC_SIGTERM (BC_VM->sig == SIGTERM || BC_VM->sig == SIGQUIT)
#else // SIGQUIT
#define BC_SIGTERM (BC_VM->sig == SIGTERM)
#endif // SIGQUIT

#define bc_vm_err(e) (bc_vm_error((e), 0))
#define bc_vm_verr(e, ...) (bc_vm_error((e), 0, __VA_ARGS__))

typedef struct BcVm {

  BcParse prs;
  BcProgram prog;

  size_t nchars;

  char *file;

  uchar sig;

  uint16_t line_len;
  uchar max_ibase;

} BcVm;

BcStatus bc_vm_posixError(BcError e, size_t line, ...);

BcStatus bc_vm_error(BcError e, size_t line, ...);

char bc_sig_msg[] = "\ninterrupt (type \"quit\" to exit)\n";

char bc_copyright[] =
  "Copyright (c) 2018 Gavin D. Howard and contributors\n"
  "Report bugs at: https://github.com/gavinhoward/bc\n\n"
  "This is free software with ABSOLUTELY NO WARRANTY.\n";

char *bc_err_fmt = "\n%s error: ";
char *bc_warn_fmt = "\n%s warning: ";
char *bc_err_line = ":%zu";

char *bc_errs[] = {
  "VM",
  "Parse",
  "Math",
  "Runtime",
  "POSIX",
};

char bc_err_ids[] = {
  BC_ERR_IDX_VM, BC_ERR_IDX_VM, BC_ERR_IDX_VM, BC_ERR_IDX_VM,
  BC_ERR_IDX_PARSE, BC_ERR_IDX_PARSE, BC_ERR_IDX_PARSE, BC_ERR_IDX_PARSE,
  BC_ERR_IDX_PARSE, BC_ERR_IDX_PARSE, BC_ERR_IDX_PARSE, BC_ERR_IDX_PARSE,
  BC_ERR_IDX_PARSE, BC_ERR_IDX_PARSE, BC_ERR_IDX_PARSE, BC_ERR_IDX_PARSE,
  BC_ERR_IDX_PARSE, BC_ERR_IDX_PARSE, BC_ERR_IDX_PARSE, BC_ERR_IDX_PARSE,
  BC_ERR_IDX_PARSE,
  BC_ERR_IDX_MATH, BC_ERR_IDX_MATH, BC_ERR_IDX_MATH, BC_ERR_IDX_MATH,
  BC_ERR_IDX_EXEC, BC_ERR_IDX_EXEC, BC_ERR_IDX_EXEC, BC_ERR_IDX_EXEC,
  BC_ERR_IDX_EXEC, BC_ERR_IDX_EXEC, BC_ERR_IDX_EXEC, BC_ERR_IDX_EXEC,
  BC_ERR_IDX_EXEC, BC_ERR_IDX_EXEC, BC_ERR_IDX_EXEC,
  BC_ERR_IDX_POSIX, BC_ERR_IDX_POSIX, BC_ERR_IDX_POSIX, BC_ERR_IDX_POSIX,
  BC_ERR_IDX_POSIX, BC_ERR_IDX_POSIX, BC_ERR_IDX_POSIX, BC_ERR_IDX_POSIX,
  BC_ERR_IDX_POSIX, BC_ERR_IDX_POSIX, BC_ERR_IDX_POSIX, BC_ERR_IDX_POSIX,
  BC_ERR_IDX_POSIX,
};

char *bc_err_msgs[] = {

  "memory allocation error",
  "I/O error",
  "file is not ASCII: %s",
  "path is a directory: %s",

  "end of file",
  "bad character (%c)",
  "string end could not be found",
  "comment end could not be found",
  "bad token",
  "name too long: must be [1, %lu]",
  "string too long: must be [1, %lu]",
  "array too long; must be [1, %lu]",
  "bad expression",
  "empty expression",
  "bad print statement",
  "bad function definition",
  "bad assignment: left side must be scale, ibase, "
    "obase, last, var, or array element",
  "no auto variable found",
  "function parameter or auto \"%s\" already exists",
  "block end could not be found",
  "cannot return a value from void function: %s()",

  "negative number",
  "non integer number",
  "overflow; %s",
  "divide by zero",

  "could not open file: %s",
  "number too long: must be [1, %lu]",
  "bad ibase; must be [%lu, %lu]",
  "bad obase; must be [%lu, %lu]",
  "bad scale; must be [%lu, %lu]",
  "bad read() expression",
  "read() call inside of a read() call",
  "variable is wrong type",
  "mismatched parameters; need %zu, have %zu",
  "undefined function: %s()",
  "cannot use a void value in an expression",

  "POSIX does not allow names longer than 1 character, like \"%s\"",
  "POSIX does not allow '#' script comments",
  "POSIX does not allow \"%s\" as a keyword",
  "POSIX does not allow a period ('.') as a shortcut for the last result",
  "POSIX requires parentheses around return expressions",
  "POSIX does not allow the \"%s\" operators",
  "POSIX does not allow comparison operators outside if or loops",
  "POSIX requires zero or one comparison operator per condition",
  "POSIX does not allow an empty init expression in a for loop",
  "POSIX does not allow an empty condition expression in a for loop",
  "POSIX does not allow an empty update expression in a for loop",
  "POSIX requires the left brace be on the same line as the function header",
  "POSIX does not allow array references as function parameters",

};

char bc_func_main[] = "(main)";
char bc_func_read[] = "(read)";

BcLexKeyword bc_lex_kws[] = {
  BC_LEX_KW_ENTRY("auto", 4, 1),
  BC_LEX_KW_ENTRY("break", 5, 1),
  BC_LEX_KW_ENTRY("continue", 8, 0),
  BC_LEX_KW_ENTRY("define", 6, 1),
  BC_LEX_KW_ENTRY("for", 3, 1),
  BC_LEX_KW_ENTRY("if", 2, 1),
  BC_LEX_KW_ENTRY("limits", 6, 0),
  BC_LEX_KW_ENTRY("return", 6, 1),
  BC_LEX_KW_ENTRY("while", 5, 1),
  BC_LEX_KW_ENTRY("halt", 4, 0),
  BC_LEX_KW_ENTRY("last", 4, 0),
  BC_LEX_KW_ENTRY("ibase", 5, 1),
  BC_LEX_KW_ENTRY("obase", 5, 1),
  BC_LEX_KW_ENTRY("scale", 5, 1),
  BC_LEX_KW_ENTRY("length", 6, 1),
  BC_LEX_KW_ENTRY("print", 5, 0),
  BC_LEX_KW_ENTRY("sqrt", 4, 1),
  BC_LEX_KW_ENTRY("abs", 3, 0),
  BC_LEX_KW_ENTRY("quit", 4, 1),
  BC_LEX_KW_ENTRY("read", 4, 0),
  BC_LEX_KW_ENTRY("else", 4, 0),
};

size_t bc_lex_kws_len = sizeof(bc_lex_kws) / sizeof(BcLexKeyword);

char *bc_parse_const1 = "1";

// This is an array that corresponds to token types. An entry is
// 1 if the token is valid in an expression, 0 otherwise.
uint8_t bc_parse_exprs[] = {
  BC_PARSE_EXPR_ENTRY(0, 0, 1, 1, 1, 1, 1, 1),
  BC_PARSE_EXPR_ENTRY(1, 1, 1, 1, 1, 1, 1, 1),
  BC_PARSE_EXPR_ENTRY(1, 1, 1, 1, 1, 1, 1, 1),
  BC_PARSE_EXPR_ENTRY(1, 1, 1, 0, 0, 1, 1, 0),
  BC_PARSE_EXPR_ENTRY(0, 0, 0, 0, 0, 0, 1, 1),
  BC_PARSE_EXPR_ENTRY(0, 0, 0, 0, 0, 0, 0, 0),
  BC_PARSE_EXPR_ENTRY(0, 0, 1, 1, 1, 1, 1, 0),
  BC_PARSE_EXPR_ENTRY(1, 1, 0, 1, 0, 0, 0, 0)
};

// This is an array of data for operators that correspond to token types.
uchar bc_parse_ops[] = {
  BC_PARSE_OP(0, 0), BC_PARSE_OP(0, 0),
  BC_PARSE_OP(1, 0), BC_PARSE_OP(1, 0),
  BC_PARSE_OP(4, 0),
  BC_PARSE_OP(5, 1), BC_PARSE_OP(5, 1), BC_PARSE_OP(5, 1),
  BC_PARSE_OP(6, 1), BC_PARSE_OP(6, 1),
  BC_PARSE_OP(9, 1), BC_PARSE_OP(9, 1), BC_PARSE_OP(9, 1),
  BC_PARSE_OP(9, 1), BC_PARSE_OP(9, 1), BC_PARSE_OP(9, 1),
  BC_PARSE_OP(11, 1), BC_PARSE_OP(10, 1),
  BC_PARSE_OP(8, 0), BC_PARSE_OP(8, 0), BC_PARSE_OP(8, 0),
  BC_PARSE_OP(8, 0), BC_PARSE_OP(8, 0), BC_PARSE_OP(8, 0),
  BC_PARSE_OP(8, 0),
};

// These identify what tokens can come after expressions in certain cases.
BcParseNext bc_parse_next_expr =
  BC_PARSE_NEXT(4, BC_LEX_NLINE, BC_LEX_SCOLON, BC_LEX_RBRACE, BC_LEX_EOF);
BcParseNext bc_parse_next_param =
  BC_PARSE_NEXT(2, BC_LEX_RPAREN, BC_LEX_COMMA);
BcParseNext bc_parse_next_print =
  BC_PARSE_NEXT(4, BC_LEX_COMMA, BC_LEX_NLINE, BC_LEX_SCOLON, BC_LEX_EOF);
BcParseNext bc_parse_next_rel = BC_PARSE_NEXT(1, BC_LEX_RPAREN);
BcParseNext bc_parse_next_elem = BC_PARSE_NEXT(1, BC_LEX_RBRACKET);
BcParseNext bc_parse_next_for = BC_PARSE_NEXT(1, BC_LEX_SCOLON);
BcParseNext bc_parse_next_read =
  BC_PARSE_NEXT(2, BC_LEX_NLINE, BC_LEX_EOF);

char bc_num_hex_digits[] = "0123456789ABCDEF";

BcNumBinaryOp bc_program_ops[] = {
  bc_num_pow, bc_num_mul, bc_num_div, bc_num_mod, bc_num_add, bc_num_sub,
};

BcNumBinaryOpReq bc_program_opReqs[] = {
  bc_num_powReq, bc_num_mulReq, bc_num_mulReq, bc_num_mulReq,
  bc_num_addReq, bc_num_addReq,
};

BcProgramUnary bc_program_unarys[] = {
  bc_program_negate, bc_program_not,
};

char bc_program_stdin_name[] = "<stdin>";
char bc_program_ready_msg[] = "ready for more input\n";
char bc_program_esc_chars[] = "ab\\efnqrt";
char bc_program_esc_seqs[] = "\a\b\\\\\f\n\"\r\t";

char *bc_lib_name = "gen/lib.bc";

char bc_lib[] = {
  115,99,97,108,101,61,50,48,10,100,101,102,105,110,101,32,101,40,120,41,123,
  10,97,117,116,111,32,98,44,115,44,110,44,114,44,100,44,105,44,112,44,102,44,
  118,10,98,61,105,98,97,115,101,10,105,98,97,115,101,61,65,10,105,102,40,120,
  60,48,41,123,10,110,61,49,10,120,61,45,120,10,125,10,115,61,115,99,97,108,101,
  10,114,61,54,43,115,43,46,52,52,42,120,10,115,99,97,108,101,61,115,99,97,108,
  101,40,120,41,43,49,10,119,104,105,108,101,40,120,62,49,41,123,10,100,43,61,
  49,10,120,47,61,50,10,115,99,97,108,101,43,61,49,10,125,10,115,99,97,108,101,
  61,114,10,114,61,120,43,49,10,112,61,120,10,102,61,118,61,49,10,102,111,114,
  40,105,61,50,59,118,59,43,43,105,41,123,10,112,42,61,120,10,102,42,61,105,10,
  118,61,112,47,102,10,114,43,61,118,10,125,10,119,104,105,108,101,40,100,45,
  45,41,114,42,61,114,10,115,99,97,108,101,61,115,10,105,98,97,115,101,61,98,
  10,105,102,40,110,41,114,101,116,117,114,110,40,49,47,114,41,10,114,101,116,
  117,114,110,40,114,47,49,41,10,125,10,100,101,102,105,110,101,32,108,40,120,
  41,123,10,97,117,116,111,32,98,44,115,44,114,44,112,44,97,44,113,44,105,44,
  118,10,98,61,105,98,97,115,101,10,105,98,97,115,101,61,65,10,105,102,40,120,
  60,61,48,41,123,10,114,61,40,49,45,49,48,94,115,99,97,108,101,41,47,49,10,105,
  98,97,115,101,61,98,10,114,101,116,117,114,110,40,114,41,10,125,10,115,61,115,
  99,97,108,101,10,115,99,97,108,101,43,61,54,10,112,61,50,10,119,104,105,108,
  101,40,120,62,61,50,41,123,10,112,42,61,50,10,120,61,115,113,114,116,40,120,
  41,10,125,10,119,104,105,108,101,40,120,60,61,46,53,41,123,10,112,42,61,50,
  10,120,61,115,113,114,116,40,120,41,10,125,10,114,61,97,61,40,120,45,49,41,
  47,40,120,43,49,41,10,113,61,97,42,97,10,118,61,49,10,102,111,114,40,105,61,
  51,59,118,59,105,43,61,50,41,123,10,97,42,61,113,10,118,61,97,47,105,10,114,
  43,61,118,10,125,10,114,42,61,112,10,115,99,97,108,101,61,115,10,105,98,97,
  115,101,61,98,10,114,101,116,117,114,110,40,114,47,49,41,10,125,10,100,101,
  102,105,110,101,32,115,40,120,41,123,10,97,117,116,111,32,98,44,115,44,114,
  44,97,44,113,44,105,10,105,102,40,120,60,48,41,114,101,116,117,114,110,40,45,
  115,40,45,120,41,41,10,98,61,105,98,97,115,101,10,105,98,97,115,101,61,65,10,
  115,61,115,99,97,108,101,10,115,99,97,108,101,61,49,46,49,42,115,43,50,10,97,
  61,97,40,49,41,10,115,99,97,108,101,61,48,10,113,61,40,120,47,97,43,50,41,47,
  52,10,120,45,61,52,42,113,42,97,10,105,102,40,113,37,50,41,120,61,45,120,10,
  115,99,97,108,101,61,115,43,50,10,114,61,97,61,120,10,113,61,45,120,42,120,
  10,102,111,114,40,105,61,51,59,97,59,105,43,61,50,41,123,10,97,42,61,113,47,
  40,105,42,40,105,45,49,41,41,10,114,43,61,97,10,125,10,115,99,97,108,101,61,
  115,10,105,98,97,115,101,61,98,10,114,101,116,117,114,110,40,114,47,49,41,10,
  125,10,100,101,102,105,110,101,32,99,40,120,41,123,10,97,117,116,111,32,98,
  44,115,10,98,61,105,98,97,115,101,10,105,98,97,115,101,61,65,10,115,61,115,
  99,97,108,101,10,115,99,97,108,101,42,61,49,46,50,10,120,61,115,40,50,42,97,
  40,49,41,43,120,41,10,115,99,97,108,101,61,115,10,105,98,97,115,101,61,98,10,
  114,101,116,117,114,110,40,120,47,49,41,10,125,10,100,101,102,105,110,101,32,
  97,40,120,41,123,10,97,117,116,111,32,98,44,115,44,114,44,110,44,97,44,109,
  44,116,44,102,44,105,44,117,10,98,61,105,98,97,115,101,10,105,98,97,115,101,
  61,65,10,110,61,49,10,105,102,40,120,60,48,41,123,10,110,61,45,49,10,120,61,
  45,120,10,125,10,105,102,40,115,99,97,108,101,60,54,53,41,123,10,105,102,40,
  120,61,61,49,41,123,10,114,61,46,55,56,53,51,57,56,49,54,51,51,57,55,52,52,
  56,51,48,57,54,49,53,54,54,48,56,52,53,56,49,57,56,55,53,55,50,49,48,52,57,
  50,57,50,51,52,57,56,52,51,55,55,54,52,53,53,50,52,51,55,51,54,49,52,56,48,
  47,110,10,105,98,97,115,101,61,98,10,114,101,116,117,114,110,40,114,41,10,125,
  10,105,102,40,120,61,61,46,50,41,123,10,114,61,46,49,57,55,51,57,53,53,53,57,
  56,52,57,56,56,48,55,53,56,51,55,48,48,52,57,55,54,53,49,57,52,55,57,48,50,
  57,51,52,52,55,53,56,53,49,48,51,55,56,55,56,53,50,49,48,49,53,49,55,54,56,
  56,57,52,48,50,47,110,10,105,98,97,115,101,61,98,10,114,101,116,117,114,110,
  40,114,41,10,125,10,125,10,115,61,115,99,97,108,101,10,105,102,40,120,62,46,
  50,41,123,10,115,99,97,108,101,43,61,53,10,97,61,97,40,46,50,41,10,125,10,115,
  99,97,108,101,61,115,43,51,10,119,104,105,108,101,40,120,62,46,50,41,123,10,
  109,43,61,49,10,120,61,40,120,45,46,50,41,47,40,49,43,46,50,42,120,41,10,125,
  10,114,61,117,61,120,10,102,61,45,120,42,120,10,116,61,49,10,102,111,114,40,
  105,61,51,59,116,59,105,43,61,50,41,123,10,117,42,61,102,10,116,61,117,47,105,
  10,114,43,61,116,10,125,10,115,99,97,108,101,61,115,10,105,98,97,115,101,61,
  98,10,114,101,116,117,114,110,40,40,109,42,97,43,114,41,47,110,41,10,125,10,
  100,101,102,105,110,101,32,106,40,110,44,120,41,123,10,97,117,116,111,32,98,
  44,115,44,111,44,97,44,105,44,118,44,102,10,98,61,105,98,97,115,101,10,105,
  98,97,115,101,61,65,10,115,61,115,99,97,108,101,10,115,99,97,108,101,61,48,
  10,110,47,61,49,10,105,102,40,110,60,48,41,123,10,110,61,45,110,10,111,61,110,
  37,50,10,125,10,97,61,49,10,102,111,114,40,105,61,50,59,105,60,61,110,59,43,
  43,105,41,97,42,61,105,10,115,99,97,108,101,61,49,46,53,42,115,10,97,61,40,
  120,94,110,41,47,50,94,110,47,97,10,114,61,118,61,49,10,102,61,45,120,42,120,
  47,52,10,115,99,97,108,101,43,61,108,101,110,103,116,104,40,97,41,45,115,99,
  97,108,101,40,97,41,10,102,111,114,40,105,61,49,59,118,59,43,43,105,41,123,
  10,118,61,118,42,102,47,105,47,40,110,43,105,41,10,114,43,61,118,10,125,10,
  115,99,97,108,101,61,115,10,105,98,97,115,101,61,98,10,105,102,40,111,41,97,
  61,45,97,10,114,101,116,117,114,110,40,97,42,114,47,49,41,10,125,10,0
};

static void bc_vec_grow(BcVec *v, size_t n) {
  size_t cap = v->cap * 2;
  while (cap < v->len + n) cap *= 2;
  v->v = xrealloc(v->v, v->size * cap);
  v->cap = cap;
}

void bc_vec_init(BcVec *v, size_t esize, BcVecFree dtor) {
  v->size = esize;
  v->cap = BC_VEC_START_CAP;
  v->len = 0;
  v->dtor = dtor;
  v->v = xmalloc(esize * BC_VEC_START_CAP);
}

void bc_vec_expand(BcVec *v, size_t req) {
  if (v->cap < req) {
    v->v = xrealloc(v->v, v->size * req);
    v->cap = req;
  }
}

void bc_vec_npop(BcVec *v, size_t n) {
  if (!v->dtor) v->len -= n;
  else {
    size_t len = v->len - n;
    while (v->len > len) v->dtor(v->v + (v->size * --v->len));
  }
}

void bc_vec_npush(BcVec *v, size_t n, void *data) {
  if (v->len + n > v->cap) bc_vec_grow(v, n);
  memcpy(v->v + (v->size * v->len), data, v->size * n);
  v->len += n;
}

void bc_vec_push(BcVec *v, void *data) {
  bc_vec_npush(v, 1, data);
}

void bc_vec_pushByte(BcVec *v, uchar data) {
  bc_vec_push(v, &data);
}

void bc_vec_pushIndex(BcVec *v, size_t idx) {

  uchar amt, nums[sizeof(size_t)];

  for (amt = 0; idx; ++amt) {
    nums[amt] = (uchar) idx;
    idx &= ((size_t) ~(UCHAR_MAX));
    idx >>= sizeof(uchar) * CHAR_BIT;
  }

  bc_vec_push(v, &amt);

  bc_vec_npush(v, amt, nums);
}

static void bc_vec_pushAt(BcVec *v, void *data, size_t idx) {

  if (idx == v->len) bc_vec_push(v, data);
  else {

    char *ptr;

    if (v->len == v->cap) bc_vec_grow(v, 1);

    ptr = v->v + v->size * idx;

    memmove(ptr + v->size, ptr, v->size * (v->len++ - idx));
    memmove(ptr, data, v->size);
  }
}

void bc_vec_string(BcVec *v, size_t len, char *str) {

  bc_vec_npop(v, v->len);
  bc_vec_expand(v, len + 1);
  memcpy(v->v, str, len);
  v->len = len;

  bc_vec_pushByte(v, '\0');
}

void bc_vec_concat(BcVec *v, char *str) {

  size_t len;

  if (!v->len) bc_vec_pushByte(v, '\0');

  len = v->len + strlen(str);

  if (v->cap < len) bc_vec_grow(v, len - v->len);
  strcat(v->v, str);

  v->len = len;
}

void bc_vec_empty(BcVec *v) {
  bc_vec_npop(v, v->len);
  bc_vec_pushByte(v, '\0');
}

void* bc_vec_item(BcVec *v, size_t idx) {
  return v->v + v->size * idx;
}

void* bc_vec_item_rev(BcVec *v, size_t idx) {
  return v->v + v->size * (v->len - idx - 1);
}

void bc_vec_free(void *vec) {
  BcVec *v = (BcVec*) vec;
  bc_vec_npop(v, v->len);
  free(v->v);
}

static size_t bc_map_find(BcVec *v, BcId *ptr) {

  size_t low = 0, high = v->len;

  while (low < high) {

    size_t mid = (low + high) / 2;
    BcId *id = bc_vec_item(v, mid);
    int result = bc_id_cmp(ptr, id);

    if (!result) return mid;
    else if (result < 0) high = mid;
    else low = mid + 1;
  }

  return low;
}

int bc_map_insert(BcVec *v, BcId *ptr, size_t *i) {

  *i = bc_map_find(v, ptr);

  if (*i == v->len) bc_vec_push(v, ptr);
  else if (!bc_id_cmp(ptr, bc_vec_item(v, *i))) return 0;
  else bc_vec_pushAt(v, ptr, *i);

  return 1;
}

size_t bc_map_index(BcVec *v, BcId *ptr) {
  size_t i = bc_map_find(v, ptr);
  if (i >= v->len) return SIZE_MAX;
  return bc_id_cmp(ptr, bc_vec_item(v, i)) ? SIZE_MAX : i;
}

static int bc_read_binary(char *buf, size_t size) {

  size_t i;

  for (i = 0; i < size; ++i) {
    if (BC_READ_BIN_CHAR(buf[i])) return 1;
  }

  return 0;
}

BcStatus bc_read_chars(BcVec *vec, char *prompt) {

  int i;
  signed char c = 0;

  bc_vec_npop(vec, vec->len);

  if (BC_TTYIN && !BC_S) {
    fputs(prompt, stderr);
    fflush(stderr);
  }

  while (!BC_SIGNAL && c != '\n') {

    i = fgetc(stdin);

    if (i == EOF) {

      if (errno == EINTR) {

        if (BC_SIGTERM) return BC_STATUS_SIGNAL;

        BC_VM->sig = 0;

        if (BC_TTYIN) {
          fputs(bc_program_ready_msg, stderr);
          if (!BC_S) fputs(prompt, stderr);
          fflush(stderr);
        }
        else return BC_STATUS_SIGNAL;

        continue;
      }

      bc_vec_pushByte(vec, '\0');
      return BC_STATUS_EOF;
    }

    c = (signed char) i;
    bc_vec_push(vec, &c);
  }

  bc_vec_pushByte(vec, '\0');

  return BC_SIGNAL ? BC_STATUS_SIGNAL : BC_STATUS_SUCCESS;
}

BcStatus bc_read_line(BcVec *vec, char *prompt) {

  BcStatus s;

  // We are about to output to stderr, so flush stdout to
  // make sure that we don't get the outputs mixed up.
  fflush(stdout);

  s = bc_read_chars(vec, prompt);
  if (s && s != BC_STATUS_EOF) return s;
  if (bc_read_binary(vec->v, vec->len - 1))
    return bc_vm_verr(BC_ERROR_VM_BIN_FILE, bc_program_stdin_name);

  return BC_STATUS_SUCCESS;
}

BcStatus bc_read_file(char *path, char **buf) {

  BcError e = BC_ERROR_VM_IO_ERR;
  FILE *f;
  size_t size, read;
  long res;
  struct stat pstat;

  f = fopen(path, "r");
  if (!f) return bc_vm_verr(BC_ERROR_EXEC_FILE_ERR, path);
  if (fstat(fileno(f), &pstat) == -1) goto malloc_err;

  if (S_ISDIR(pstat.st_mode)) {
    e = BC_ERROR_VM_PATH_DIR;
    goto malloc_err;
  }

  if (fseek(f, 0, SEEK_END) == -1) goto malloc_err;
  res = ftell(f);
  if (res < 0) goto malloc_err;
  if (fseek(f, 0, SEEK_SET) == -1) goto malloc_err;

  size = (size_t) res;
  *buf = xmalloc(size + 1);

  read = fread(*buf, 1, size, f);
  if (read != size) goto read_err;

  (*buf)[size] = '\0';

  if (bc_read_binary(*buf, size)) {
    e = BC_ERROR_VM_BIN_FILE;
    goto read_err;
  }

  fclose(f);

  return BC_STATUS_SUCCESS;

read_err:
  free(*buf);
malloc_err:
  fclose(f);
  return bc_vm_verr(e, path);
}

static void bc_num_setToZero(BcNum *n, size_t scale) {
  n->len = 0;
  n->neg = 0;
  n->rdx = scale;
}

static void bc_num_zero(BcNum *n) {
  bc_num_setToZero(n, 0);
}

void bc_num_one(BcNum *n) {
  bc_num_setToZero(n, 0);
  n->len = 1;
  n->num[0] = 1;
}

void bc_num_ten(BcNum *n) {
  bc_num_setToZero(n, 0);
  n->len = 2;
  n->num[0] = 0;
  n->num[1] = 1;
}

static size_t bc_num_log10(size_t i) {
  size_t len;
  for (len = 1; i; i /= 10, ++len);
  return len;
}

static BcStatus bc_num_subArrays(BcDig *a, BcDig *b, size_t len)
{
  size_t i, j;
  for (i = 0; !BC_SIGNAL && i < len; ++i) {
    for (a[i] -= b[i], j = 0; !BC_SIGNAL && a[i + j] < 0;) {
      a[i + j++] += 10;
      a[i + j] -= 1;
    }
  }
  return BC_SIGNAL ? BC_STATUS_SIGNAL : BC_STATUS_SUCCESS;
}

static ssize_t bc_num_compare(BcDig *a, BcDig *b, size_t len)
{
  size_t i;
  int c = 0;
  for (i = len - 1; !BC_SIGNAL && i < len && !(c = a[i] - b[i]); --i);
  return BC_NUM_NEG(i + 1, c < 0);
}

ssize_t bc_num_cmp(BcNum *a, BcNum *b) {

  size_t i, min, a_int, b_int, diff;
  BcDig *max_num, *min_num;
  int a_max, neg = 0;
  ssize_t cmp;

  if (a == b) return 0;
  if (!a->len) return BC_NUM_NEG(b->len != 0, !b->neg);
  if (!b->len) return BC_NUM_CMP_ZERO(a);
  if (a->neg) {
    if (b->neg) neg = 1;
    else return -1;
  }
  else if (b->neg) return 1;

  a_int = BC_NUM_INT(a);
  b_int = BC_NUM_INT(b);
  a_int -= b_int;
  a_max = (a->rdx > b->rdx);

  if (a_int) return (ssize_t) a_int;

  if (a_max) {
    min = b->rdx;
    diff = a->rdx - b->rdx;
    max_num = a->num + diff;
    min_num = b->num;
  }
  else {
    min = a->rdx;
    diff = b->rdx - a->rdx;
    max_num = b->num + diff;
    min_num = a->num;
  }

  cmp = bc_num_compare(max_num, min_num, b_int + min);
  if (cmp) return BC_NUM_NEG(cmp, (!a_max) != neg);

  for (max_num -= diff, i = diff - 1; !BC_SIGNAL && i < diff; --i) {
    if (max_num[i]) return BC_NUM_NEG(1, (!a_max) != neg);
  }

  return 0;
}

static void bc_num_clean(BcNum *n) {
  while (n->len && !n->num[n->len - 1]) --n->len;
  if (!n->len) n->neg = 0;
  else if (n->len < n->rdx) n->len = n->rdx;
}

void bc_num_truncate(BcNum *n, size_t places) {

  if (!places) return;

  n->rdx -= places;

  if (n->len) {
    n->len -= places;
    memmove(n->num, n->num + places, n->len * sizeof(BcDig));
    bc_num_clean(n);
  }
}

static void bc_num_extend(BcNum *n, size_t places) {

  size_t len = n->len + places;

  if (!places) return;

  if (n->cap < len) bc_num_expand(n, len);

  memmove(n->num + places, n->num, sizeof(BcDig) * n->len);
  memset(n->num, 0, sizeof(BcDig) * places);

  if (n->len) n->len += places;

  n->rdx += places;
}

static void bc_num_retireMul(BcNum *n, size_t scale, int neg1, int neg2) {

  if (n->rdx < scale) bc_num_extend(n, scale - n->rdx);
  else bc_num_truncate(n, n->rdx - scale);

  bc_num_clean(n);
  if (n->len) n->neg = (!neg1 != !neg2);
}

static void bc_num_split(BcNum *n, size_t idx, BcNum *a, BcNum *b) {

  if (idx < n->len) {

    b->len = n->len - idx;
    a->len = idx;
    a->rdx = b->rdx = 0;

    memcpy(b->num, n->num + idx, b->len * sizeof(BcDig));
    memcpy(a->num, n->num, idx * sizeof(BcDig));

    bc_num_clean(b);
  }
  else bc_num_copy(a, n);

  bc_num_clean(a);
}

static BcStatus bc_num_shift(BcNum *n, size_t places) {

  if (!places || !n->len) return BC_STATUS_SUCCESS;
  if (places + n->len > BC_MAX_NUM)
    return bc_vm_verr(BC_ERROR_MATH_OVERFLOW, "shifted left too far");

  if (n->rdx >= places) n->rdx -= places;
  else {
    bc_num_extend(n, places - n->rdx);
    n->rdx = 0;
  }

  bc_num_clean(n);

  return BC_STATUS_SUCCESS;
}

static BcStatus bc_num_inv(BcNum *a, BcNum *b, size_t scale) {

  BcNum one;
  BcDig num[2];

  one.cap = 2;
  one.num = num;
  bc_num_one(&one);

  return bc_num_div(&one, a, b, scale);
}

static unsigned int bc_num_addDigit(BcDig *num, unsigned int d, unsigned int c)
{
  d += c;
  *num = (BcDig) (d % 10);
  return d / 10;
}

static BcStatus bc_num_a(BcNum *a, BcNum *b, BcNum *c, size_t sub) {

  BcDig *ptr, *ptr_a, *ptr_b, *ptr_c;
  size_t i, max, min_rdx, min_int, diff, a_int, b_int;
  unsigned int carry;

  // Because this function doesn't need to use scale (per the bc spec),
  // I am hijacking it to say whether it's doing an add or a subtract.

  if (!a->len) {
    bc_num_copy(c, b);
    if (sub && c->len) c->neg = !c->neg;
    return BC_STATUS_SUCCESS;
  }
  if (!b->len) {
    bc_num_copy(c, a);
    return BC_STATUS_SUCCESS;
  }

  c->neg = a->neg;
  c->rdx = maxof(a->rdx, b->rdx);
  min_rdx = minof(a->rdx, b->rdx);

  if (a->rdx > b->rdx) {
    diff = a->rdx - b->rdx;
    ptr = a->num;
    ptr_a = a->num + diff;
    ptr_b = b->num;
  }
  else {
    diff = b->rdx - a->rdx;
    ptr = b->num;
    ptr_a = a->num;
    ptr_b = b->num + diff;
  }

  for (ptr_c = c->num, i = 0; i < diff; ++i) ptr_c[i] = ptr[i];

  c->len = diff;
  ptr_c += diff;
  a_int = BC_NUM_INT(a);
  b_int = BC_NUM_INT(b);

  if (a_int > b_int) {
    min_int = b_int;
    max = a_int;
    ptr = ptr_a;
  }
  else {
    min_int = a_int;
    max = b_int;
    ptr = ptr_b;
  }

  for (carry = 0, i = 0; !BC_SIGNAL && i < min_rdx + min_int; ++i) {
    unsigned int in = (unsigned int) (ptr_a[i] + ptr_b[i]);
    carry = bc_num_addDigit(ptr_c + i, in, carry);
  }

  for (; !BC_SIGNAL && i < max + min_rdx; ++i)
    carry = bc_num_addDigit(ptr_c + i, (unsigned int) ptr[i], carry);

  c->len += i;

  if (carry) c->num[c->len++] = (BcDig) carry;

  return BC_SIGNAL ? BC_STATUS_SIGNAL : BC_STATUS_SUCCESS;
}

static BcStatus bc_num_s(BcNum *a, BcNum *b, BcNum *c, size_t sub) {

  BcStatus s;
  ssize_t cmp;
  BcNum *minuend, *subtrahend;
  size_t start;
  int aneg, bneg, neg;

  // Because this function doesn't need to use scale (per the bc spec),
  // I am hijacking it to say whether it's doing an add or a subtract.

  if (!a->len) {
    bc_num_copy(c, b);
    if (sub && c->len) c->neg = !c->neg;
    return BC_STATUS_SUCCESS;
  }
  if (!b->len) {
    bc_num_copy(c, a);
    return BC_STATUS_SUCCESS;
  }

  aneg = a->neg;
  bneg = b->neg;
  a->neg = b->neg = 0;

  cmp = bc_num_cmp(a, b);

  a->neg = aneg;
  b->neg = bneg;

  if (!cmp) {
    bc_num_setToZero(c, maxof(a->rdx, b->rdx));
    return BC_STATUS_SUCCESS;
  }

  if (cmp > 0) {
    neg = a->neg;
    minuend = a;
    subtrahend = b;
  }
  else {
    neg = b->neg;
    if (sub) neg = !neg;
    minuend = b;
    subtrahend = a;
  }

  bc_num_copy(c, minuend);
  c->neg = neg;

  if (c->rdx < subtrahend->rdx) {
    bc_num_extend(c, subtrahend->rdx - c->rdx);
    start = 0;
  }
  else start = c->rdx - subtrahend->rdx;

  s = bc_num_subArrays(c->num + start, subtrahend->num, subtrahend->len);

  bc_num_clean(c);

  return s;
}

static BcStatus bc_num_k(BcNum *a, BcNum *b, BcNum *c) {

  BcStatus s;
  size_t max = maxof(a->len, b->len), max2 = (max + 1) / 2;
  BcNum l1, h1, l2, h2, m2, m1, z0, z1, z2, temp;
  int aone = BC_NUM_ONE(a);

  // This is here because the function is recursive.
  if (BC_SIGNAL) return BC_STATUS_SIGNAL;
  if (!a->len || !b->len) {
    bc_num_zero(c);
    return BC_STATUS_SUCCESS;
  }
  if (aone || BC_NUM_ONE(b)) {
    bc_num_copy(c, aone ? b : a);
    return BC_STATUS_SUCCESS;
  }

  if (a->len + b->len < BC_NUM_KARATSUBA_LEN ||
      a->len < BC_NUM_KARATSUBA_LEN || b->len < BC_NUM_KARATSUBA_LEN)
  {
    size_t i, j, len;
    unsigned int carry;
    BcDig *ptr_c;

    bc_num_expand(c, a->len + b->len + 1);

    ptr_c = c->num;
    memset(ptr_c, 0, sizeof(BcDig) * c->cap);
    c->len = len = 0;

    for (i = 0; !BC_SIGNAL && i < b->len; ++i) {

      BcDig *ptr = ptr_c + i;

      carry = 0;

      for (j = 0; !BC_SIGNAL && j < a->len; ++j) {
        unsigned int in = (uchar) ptr[j];
        in += ((unsigned int) a->num[j]) * ((unsigned int) b->num[i]);
        carry = bc_num_addDigit(ptr + j, in, carry);
      }

      ptr[j] += (BcDig) carry;
      len = maxof(len, i + j + (carry != 0));
    }

    c->len = len;

    return BC_SIGNAL ? BC_STATUS_SIGNAL : BC_STATUS_SUCCESS;
  }

  bc_num_init(&l1, max);
  bc_num_init(&h1, max);
  bc_num_init(&l2, max);
  bc_num_init(&h2, max);
  bc_num_init(&m1, max);
  bc_num_init(&m2, max);
  bc_num_init(&z0, max);
  bc_num_init(&z1, max);
  bc_num_init(&z2, max);
  bc_num_init(&temp, max + max);

  bc_num_split(a, max2, &l1, &h1);
  bc_num_split(b, max2, &l2, &h2);

  s = bc_num_add(&h1, &l1, &m1, 0);
  if (s) goto err;
  s = bc_num_add(&h2, &l2, &m2, 0);
  if (s) goto err;

  s = bc_num_k(&h1, &h2, &z0);
  if (s) goto err;
  s = bc_num_k(&m1, &m2, &z1);
  if (s) goto err;
  s = bc_num_k(&l1, &l2, &z2);
  if (s) goto err;

  s = bc_num_sub(&z1, &z0, &temp, 0);
  if (s) goto err;
  s = bc_num_sub(&temp, &z2, &z1, 0);
  if (s) goto err;

  s = bc_num_shift(&z0, max2 * 2);
  if (s) goto err;
  s = bc_num_shift(&z1, max2);
  if (s) goto err;
  s = bc_num_add(&z0, &z1, &temp, 0);
  if (s) goto err;
  s = bc_num_add(&temp, &z2, c, 0);

err:
  bc_num_free(&temp);
  bc_num_free(&z2);
  bc_num_free(&z1);
  bc_num_free(&z0);
  bc_num_free(&m2);
  bc_num_free(&m1);
  bc_num_free(&h2);
  bc_num_free(&l2);
  bc_num_free(&h1);
  bc_num_free(&l1);
  return s;
}

static BcStatus bc_num_m(BcNum *a, BcNum *b, BcNum *c, size_t scale) {

  BcStatus s;
  BcNum cpa, cpb;
  size_t maxrdx = maxof(a->rdx, b->rdx);

  scale = maxof(scale, a->rdx);
  scale = maxof(scale, b->rdx);
  scale = minof(a->rdx + b->rdx, scale);
  maxrdx = maxof(maxrdx, scale);

  bc_num_createCopy(&cpa, a);
  bc_num_createCopy(&cpb, b);

  cpa.neg = cpb.neg = 0;

  s = bc_num_shift(&cpa, maxrdx);
  if (s) goto err;
  s = bc_num_shift(&cpb, maxrdx);
  if (s) goto err;
  s = bc_num_k(&cpa, &cpb, c);
  if (s) goto err;

  maxrdx += scale;
  bc_num_expand(c, c->len + maxrdx);

  if (c->len < maxrdx) {
    memset(c->num + c->len, 0, (c->cap - c->len) * sizeof(BcDig));
    c->len += maxrdx;
  }

  c->rdx = maxrdx;
  bc_num_retireMul(c, scale, a->neg, b->neg);

err:
  bc_num_free(&cpb);
  bc_num_free(&cpa);
  return s;
}

static BcStatus bc_num_d(BcNum *a, BcNum *b, BcNum *c, size_t scale) {

  BcStatus s = BC_STATUS_SUCCESS;
  BcDig *n, *p, q;
  size_t len, end, i;
  BcNum cp;
  int zero = 1;

  if (!b->len) return bc_vm_err(BC_ERROR_MATH_DIVIDE_BY_ZERO);
  if (!a->len) {
    bc_num_setToZero(c, scale);
    return BC_STATUS_SUCCESS;
  }
  if (BC_NUM_ONE(b)) {
    bc_num_copy(c, a);
    bc_num_retireMul(c, scale, a->neg, b->neg);
    return BC_STATUS_SUCCESS;
  }

  bc_num_init(&cp, bc_num_mulReq(a, b, scale));
  bc_num_copy(&cp, a);
  len = b->len;

  if (len > cp.len) {
    bc_num_expand(&cp, len + 2);
    bc_num_extend(&cp, len - cp.len);
  }

  if (b->rdx > cp.rdx) bc_num_extend(&cp, b->rdx - cp.rdx);
  cp.rdx -= b->rdx;
  if (scale > cp.rdx) bc_num_extend(&cp, scale - cp.rdx);

  if (b->rdx == b->len) {
    for (i = 0; zero && i < len; ++i) zero = !b->num[len - i - 1];
    len -= i - 1;
  }

  if (cp.cap == cp.len) bc_num_expand(&cp, cp.len + 1);

  // We want an extra zero in front to make things simpler.
  cp.num[cp.len++] = 0;
  end = cp.len - len;

  bc_num_expand(c, cp.len);

  memset(c->num + end, 0, (c->cap - end) * sizeof(BcDig));
  c->rdx = cp.rdx;
  c->len = cp.len;
  p = b->num;

  for (i = end - 1; !BC_SIGNAL && !s && i < end; --i) {
    n = cp.num + i;
    for (q = 0; !s && (n[len] || bc_num_compare(n, p, len) >= 0); ++q)
      s = bc_num_subArrays(n, p, len);
    c->num[i] = q;
  }

  if (!s) bc_num_retireMul(c, scale, a->neg, b->neg);
  bc_num_free(&cp);

  return s;
}

static BcStatus bc_num_r(BcNum *a, BcNum *b, BcNum *c, BcNum *d, size_t scale,
                  size_t ts)
{
  BcStatus s;
  BcNum temp;
  int neg;

  if (!b->len) return bc_vm_err(BC_ERROR_MATH_DIVIDE_BY_ZERO);
  if (!a->len) {
    bc_num_setToZero(c, ts);
    bc_num_setToZero(d, ts);
    return BC_STATUS_SUCCESS;
  }

  bc_num_init(&temp, d->cap);
  bc_num_d(a, b, c, scale);

  if (scale) scale = ts;

  s = bc_num_m(c, b, &temp, scale);
  if (s) goto err;
  s = bc_num_sub(a, &temp, d, scale);
  if (s) goto err;

  if (ts > d->rdx && d->len) bc_num_extend(d, ts - d->rdx);

  neg = d->neg;
  bc_num_retireMul(d, ts, a->neg, b->neg);
  d->neg = neg;

err:
  bc_num_free(&temp);
  return s;
}

static BcStatus bc_num_rem(BcNum *a, BcNum *b, BcNum *c, size_t scale) {

  BcStatus s;
  BcNum c1;
  size_t ts = maxof(scale + b->rdx, a->rdx), len = bc_num_mulReq(a, b, ts);

  bc_num_init(&c1, len);
  s = bc_num_r(a, b, &c1, c, scale, ts);
  bc_num_free(&c1);

  return s;
}

static BcStatus bc_num_p(BcNum *a, BcNum *b, BcNum *c, size_t scale) {

  BcStatus s = BC_STATUS_SUCCESS;
  BcNum copy;
  unsigned long pow = 0;
  size_t i, powrdx, resrdx;
  int neg, zero;

  if (b->rdx) return bc_vm_err(BC_ERROR_MATH_NON_INTEGER);

  if (!b->len) {
    bc_num_one(c);
    return BC_STATUS_SUCCESS;
  }
  if (!a->len) {
    bc_num_setToZero(c, scale);
    return BC_STATUS_SUCCESS;
  }
  if (BC_NUM_ONE(b)) {
    if (!b->neg) bc_num_copy(c, a);
    else s = bc_num_inv(a, c, scale);
    return s;
  }

  neg = b->neg;
  b->neg = 0;
  s = bc_num_ulong(b, &pow);
  b->neg = neg;
  if (s) return s;

  bc_num_createCopy(&copy, a);

  if (!neg) scale = minof(a->rdx * pow, maxof(scale, a->rdx));

  for (powrdx = a->rdx; !BC_SIGNAL && !(pow & 1); pow >>= 1) {
    powrdx <<= 1;
    s = bc_num_mul(&copy, &copy, &copy, powrdx);
    if (s) goto err;
  }

  if (BC_SIGNAL) {
    s = BC_STATUS_SIGNAL;
    goto err;
  }

  bc_num_copy(c, &copy);
  resrdx = powrdx;

  while (!BC_SIGNAL && (pow >>= 1)) {

    powrdx <<= 1;
    s = bc_num_mul(&copy, &copy, &copy, powrdx);
    if (s) goto err;

    if (pow & 1) {
      resrdx += powrdx;
      s = bc_num_mul(c, &copy, c, resrdx);
      if (s) goto err;
    }
  }

  if (neg) {
    s = bc_num_inv(c, c, scale);
    if (s) goto err;
  }

  if (BC_SIGNAL) {
    s = BC_STATUS_SIGNAL;
    goto err;
  }

  if (c->rdx > scale) bc_num_truncate(c, c->rdx - scale);

  // We can't use bc_num_clean() here.
  for (zero = 1, i = 0; zero && i < c->len; ++i) zero = !c->num[i];
  if (zero) bc_num_setToZero(c, scale);

err:
  bc_num_free(&copy);
  return s;
}

static BcStatus bc_num_binary(BcNum *a, BcNum *b, BcNum *c, size_t scale,
                              BcNumBinaryOp op, size_t req)
{
  BcStatus s;
  BcNum num2, *ptr_a, *ptr_b;
  int init = 0;

  if (c == a) {
    ptr_a = &num2;
    memcpy(ptr_a, c, sizeof(BcNum));
    init = 1;
  }
  else ptr_a = a;

  if (c == b) {
    ptr_b = &num2;
    if (c != a) {
      memcpy(ptr_b, c, sizeof(BcNum));
      init = 1;
    }
  }
  else ptr_b = b;

  if (init) bc_num_init(c, req);
  else bc_num_expand(c, req);

  s = op(ptr_a, ptr_b, c, scale);

  if (init) bc_num_free(&num2);

  return s;
}

static unsigned long bc_num_parseChar(char c, size_t base_t) {

  if (isupper(c)) {
    c = BC_NUM_NUM_LETTER(c);
    c = ((size_t) c) >= base_t ? (char) base_t - 1 : c;
  }
  else c -= '0';

  return (unsigned long) (uchar) c;
}

static void bc_num_parseDecimal(BcNum *n, char *val) {

  size_t len, i;
  char *ptr;
  int zero = 1;

  for (i = 0; val[i] == '0'; ++i);

  val += i;
  len = strlen(val);

  if (len) {
    for (i = 0; zero && i < len; ++i) zero = (val[i] == '0') || val[i] == '.';
    bc_num_expand(n, len);
  }

  ptr = strchr(val, '.');

  // Explicitly test for NULL here to produce either a 0 or 1.
  n->rdx = (size_t) ((ptr != NULL) * ((val + len) - (ptr + 1)));

  if (!zero) {
    for (i = len - 1; i < len; ++n->len, --i) {

      char c = val[i];

      if (c == '.') n->len -= 1;
      else {
        if (isupper(c)) c = '9';
        n->num[n->len] = c - '0';
      }
    }
  }
}

static BcStatus bc_num_parseBase(BcNum *n, char *val,
                                 BcNum *base, size_t base_t)
{
  BcStatus s = BC_STATUS_SUCCESS;
  BcNum temp, mult, result;
  BcDig c = 0;
  int zero = 1;
  unsigned long v;
  size_t i, digits, len = strlen(val);

  for (i = 0; zero && i < len; ++i) zero = (val[i] == '.' || val[i] == '0');
  if (zero) return BC_STATUS_SUCCESS;

  bc_num_init(&temp, BC_NUM_LONG_LOG10);
  bc_num_init(&mult, BC_NUM_LONG_LOG10);

  for (i = 0; i < len && (c = val[i]) && c != '.'; ++i) {

    v = bc_num_parseChar(c, base_t);

    s = bc_num_mul(n, base, &mult, 0);
    if (s) goto int_err;
    bc_num_ulong2num(&temp, v);
    s = bc_num_add(&mult, &temp, n, 0);
    if (s) goto int_err;
  }

  if (i == len && !(c = val[i])) goto int_err;

  bc_num_init(&result, base->len);
  bc_num_one(&mult);

  for (i += 1, digits = 0; i < len && (c = val[i]); ++i, ++digits) {

    v = bc_num_parseChar(c, base_t);

    s = bc_num_mul(&result, base, &result, 0);
    if (s) goto err;
    bc_num_ulong2num(&temp, v);
    s = bc_num_add(&result, &temp, &result, 0);
    if (s) goto err;

    s = bc_num_mul(&mult, base, &mult, 0);
    if (s) goto err;
  }

  s = bc_num_div(&result, &mult, &result, digits);
  if (s) goto err;
  s = bc_num_add(n, &result, n, digits);
  if (s) goto err;

  if (n->len) {
    if (n->rdx < digits) bc_num_extend(n, digits - n->rdx);
  }
  else bc_num_zero(n);

err:
  bc_num_free(&result);
int_err:
  bc_num_free(&mult);
  bc_num_free(&temp);
  return s;
}

static void bc_num_printNewline() {
  if (BC_VM->nchars >= (size_t) (BC_VM->line_len - 1)) {
    putchar('\\');
    putchar('\n');
    BC_VM->nchars = 0;
  }
}

static void bc_num_printDigits(size_t n, size_t len, int rdx) {

  size_t exp, pow;

  bc_num_printNewline();
  putchar(rdx ? '.' : ' ');
  ++BC_VM->nchars;

  bc_num_printNewline();
  for (exp = 0, pow = 1; exp < len - 1; ++exp, pow *= 10);

  for (exp = 0; exp < len; pow /= 10, ++BC_VM->nchars, ++exp) {
    size_t dig;
    bc_num_printNewline();
    dig = n / pow;
    n -= dig * pow;
    putchar(((uchar) dig) + '0');
  }
}

static void bc_num_printHex(size_t n, size_t len, int rdx) {

  if (rdx) {
    bc_num_printNewline();
    putchar('.');
    BC_VM->nchars += 1;
  }

  bc_num_printNewline();
  putchar(bc_num_hex_digits[n]);
  BC_VM->nchars += len;
}

static void bc_num_printDecimal(BcNum *n) {

  size_t i, rdx = n->rdx - 1;

  if (n->neg) putchar('-');
  BC_VM->nchars += n->neg;

  for (i = n->len - 1; i < n->len; --i)
    bc_num_printHex((size_t) n->num[i], 1, i == rdx);
}

static BcStatus bc_num_printNum(BcNum *n, BcNum *base,
                                size_t len, BcNumDigitOp print)
{
  BcStatus s;
  BcVec stack;
  BcNum intp, fracp, digit, frac_len;
  unsigned long dig, *ptr;
  size_t i;
  int radix;

  if (!n->len) {
    print(0, len, 0);
    return BC_STATUS_SUCCESS;
  }

  bc_vec_init(&stack, sizeof(unsigned long), NULL);
  bc_num_init(&fracp, n->rdx);
  bc_num_init(&digit, len);
  bc_num_init(&frac_len, BC_NUM_INT(n));
  bc_num_one(&frac_len);
  bc_num_createCopy(&intp, n);

  bc_num_truncate(&intp, intp.rdx);
  s = bc_num_sub(n, &intp, &fracp, 0);
  if (s) goto err;

  while (intp.len) {
    s = bc_num_divmod(&intp, base, &intp, &digit, 0);
    if (s) goto err;
    s = bc_num_ulong(&digit, &dig);
    if (s) goto err;
    bc_vec_push(&stack, &dig);
  }

  for (i = 0; i < stack.len; ++i) {
    ptr = bc_vec_item_rev(&stack, i);
    print(*ptr, len, 0);
  }

  if (!n->rdx) goto err;

  for (radix = 1; frac_len.len <= n->rdx; radix = 0) {
    s = bc_num_mul(&fracp, base, &fracp, n->rdx);
    if (s) goto err;
    s = bc_num_ulong(&fracp, &dig);
    if (s) goto err;
    bc_num_ulong2num(&intp, dig);
    s = bc_num_sub(&fracp, &intp, &fracp, 0);
    if (s) goto err;
    print(dig, len, radix);
    s = bc_num_mul(&frac_len, base, &frac_len, 0);
    if (s) goto err;
  }

err:
  bc_num_free(&frac_len);
  bc_num_free(&digit);
  bc_num_free(&fracp);
  bc_num_free(&intp);
  bc_vec_free(&stack);
  return s;
}

static BcStatus bc_num_printBase(BcNum *n, BcNum *base, size_t base_t) {

  BcStatus s;
  size_t width;
  BcNumDigitOp print;
  int neg = n->neg;

  if (neg) putchar('-');
  BC_VM->nchars += neg;

  n->neg = 0;

  if (base_t <= BC_NUM_MAX_POSIX_IBASE) {
    width = 1;
    print = bc_num_printHex;
  }
  else {
    width = bc_num_log10(base_t - 1) - 1;
    print = bc_num_printDigits;
  }

  s = bc_num_printNum(n, base, width, print);
  n->neg = neg;

  return s;
}

void bc_num_setup(BcNum *n, BcDig *num, size_t cap) {
  n->num = num;
  n->cap = cap;
  n->rdx = n->len = 0;
  n->neg = 0;
}

void bc_num_init(BcNum *n, size_t req) {
  req = req >= BC_NUM_DEF_SIZE ? req : BC_NUM_DEF_SIZE;
  bc_num_setup(n, xmalloc(req), req);
}

void bc_num_expand(BcNum *n, size_t req) {
  req = req >= BC_NUM_DEF_SIZE ? req : BC_NUM_DEF_SIZE;
  if (req > n->cap) {
    n->num = xrealloc(n->num, req);
    n->cap = req;
  }
}

void bc_num_free(void *num) {
  free(((BcNum*) num)->num);
}

void bc_num_copy(BcNum *d, BcNum *s) {
  if (d == s) return;
  bc_num_expand(d, s->len);
  d->len = s->len;
  d->neg = s->neg;
  d->rdx = s->rdx;
  memcpy(d->num, s->num, sizeof(BcDig) * d->len);
}

void bc_num_createCopy(BcNum *d, BcNum *s) {
  bc_num_init(d, s->len);
  bc_num_copy(d, s);
}

void bc_num_createFromUlong(BcNum *n, unsigned long val) {
  bc_num_init(n, BC_NUM_LONG_LOG10);
  bc_num_ulong2num(n, val);
}

BcStatus bc_num_parse(BcNum *n, char *val,
                      BcNum *base, size_t base_t, int letter)
{
  BcStatus s = BC_STATUS_SUCCESS;

  if (letter) bc_num_ulong2num(n, bc_num_parseChar(val[0], BC_NUM_MAX_LBASE));
  else if (base_t == 10) bc_num_parseDecimal(n, val);
  else s = bc_num_parseBase(n, val, base, base_t);

  return s;
}

BcStatus bc_num_print(BcNum *n, BcNum *base,
                      size_t base_t, int newline)
{
  BcStatus s = BC_STATUS_SUCCESS;

  bc_num_printNewline();

  if (!n->len) bc_num_printHex(0, 1, 0);
  else if (base_t == 10) bc_num_printDecimal(n);
  else s = bc_num_printBase(n, base, base_t);

  if (!s && newline) {
    putchar('\n');
    BC_VM->nchars = 0;
  }

  return s;
}

BcStatus bc_num_ulong(BcNum *n, unsigned long *result) {

  size_t i;
  unsigned long pow, r;

  *result = 0;

  if (n->neg) return bc_vm_err(BC_ERROR_MATH_NEGATIVE);

  for (r = 0, pow = 1, i = n->rdx; i < n->len; ++i) {

    unsigned long prev = r, powprev = pow;

    r += ((unsigned long) n->num[i]) * pow;
    pow *= 10;

    if (r < prev || pow < powprev)
      return bc_vm_verr(BC_ERROR_MATH_OVERFLOW, "number cannot fit");
  }

  *result = r;

  return BC_STATUS_SUCCESS;
}

void bc_num_ulong2num(BcNum *n, unsigned long val) {

  size_t len;
  BcDig *ptr;
  unsigned long i;

  bc_num_zero(n);

  if (!val) return;

  len = bc_num_log10(ULONG_MAX);
  bc_num_expand(n, len);
  for (ptr = n->num, i = 0; val; ++i, ++n->len, val /= 10) ptr[i] = val % 10;
}

size_t bc_num_addReq(BcNum *a, BcNum *b, size_t scale) {
  BC_UNUSED(scale);
  return maxof(a->rdx, b->rdx) + maxof(BC_NUM_INT(a), BC_NUM_INT(b)) + 1;
}

size_t bc_num_mulReq(BcNum *a, BcNum *b, size_t scale) {
  return BC_NUM_INT(a) + BC_NUM_INT(b) + maxof(scale, a->rdx + b->rdx) + 1;
}

size_t bc_num_powReq(BcNum *a, BcNum *b, size_t scale) {
  BC_UNUSED(scale);
  return BC_NUM_PREQ(a, b);
}

BcStatus bc_num_add(BcNum *a, BcNum *b, BcNum *c, size_t scale) {
  BcNumBinaryOp op = (!a->neg == !b->neg) ? bc_num_a : bc_num_s;
  BC_UNUSED(scale);
  return bc_num_binary(a, b, c, 0, op, bc_num_addReq(a, b, scale));
}

BcStatus bc_num_sub(BcNum *a, BcNum *b, BcNum *c, size_t scale) {
  BcNumBinaryOp op = (!a->neg == !b->neg) ? bc_num_s : bc_num_a;
  BC_UNUSED(scale);
  return bc_num_binary(a, b, c, 1, op, bc_num_addReq(a, b, scale));
}

BcStatus bc_num_mul(BcNum *a, BcNum *b, BcNum *c, size_t scale) {
  return bc_num_binary(a, b, c, scale, bc_num_m, bc_num_mulReq(a, b, scale));
}

BcStatus bc_num_div(BcNum *a, BcNum *b, BcNum *c, size_t scale) {
  return bc_num_binary(a, b, c, scale, bc_num_d, bc_num_mulReq(a, b, scale));
}

BcStatus bc_num_mod(BcNum *a, BcNum *b, BcNum *c, size_t scale) {
  return bc_num_binary(a, b, c, scale, bc_num_rem, bc_num_mulReq(a, b, scale));
}

BcStatus bc_num_pow(BcNum *a, BcNum *b, BcNum *c, size_t scale) {
  return bc_num_binary(a, b, c, scale, bc_num_p, BC_NUM_PREQ(a, b));
}

BcStatus bc_num_sqrt(BcNum *a, BcNum *b, size_t scale) {

  BcStatus s = BC_STATUS_SUCCESS;
  BcNum num1, num2, half, f, fprime, *x0, *x1, *temp;
  size_t pow, len, digs, digs1, resrdx, times = 0;
  ssize_t cmp = 1, cmp1 = SSIZE_MAX, cmp2 = SSIZE_MAX;
  BcDig half_digs[2];

  bc_num_init(b, maxof(scale, a->rdx) + ((BC_NUM_INT(a) + 1) >> 1) + 1);

  if (!a->len) {
    bc_num_setToZero(b, scale);
    return BC_STATUS_SUCCESS;
  }
  if (a->neg) return bc_vm_err(BC_ERROR_MATH_NEGATIVE);
  if (BC_NUM_ONE(a)) {
    bc_num_one(b);
    bc_num_extend(b, scale);
    return BC_STATUS_SUCCESS;
  }

  scale = maxof(scale, a->rdx) + 1;
  len = a->len + scale;

  bc_num_init(&num1, len);
  bc_num_init(&num2, len);
  bc_num_setup(&half, half_digs, sizeof(half_digs) / sizeof(BcDig));

  bc_num_one(&half);
  half.num[0] = 5;
  half.rdx = 1;

  bc_num_init(&f, len);
  bc_num_init(&fprime, len);

  x0 = &num1;
  x1 = &num2;

  bc_num_one(x0);
  pow = BC_NUM_INT(a);

  if (pow) {

    if (pow & 1) x0->num[0] = 2;
    else x0->num[0] = 6;

    pow -= 2 - (pow & 1);

    bc_num_extend(x0, pow);

    // Make sure to move the radix back.
    x0->rdx -= pow;
  }

  x0->rdx = digs = digs1 = 0;
  resrdx = scale + 2;
  len = BC_NUM_INT(x0) + resrdx - 1;

  while (!BC_SIGNAL && (cmp || digs < len)) {

    s = bc_num_div(a, x0, &f, resrdx);
    if (s) goto err;
    s = bc_num_add(x0, &f, &fprime, resrdx);
    if (s) goto err;
    s = bc_num_mul(&fprime, &half, x1, resrdx);
    if (s) goto err;

    cmp = bc_num_cmp(x1, x0);
    digs = x1->len - (unsigned long long) llabs(cmp);

    if (cmp == cmp2 && digs == digs1) times += 1;
    else times = 0;

    resrdx += times > 4;

    cmp2 = cmp1;
    cmp1 = cmp;
    digs1 = digs;

    temp = x0;
    x0 = x1;
    x1 = temp;
  }

  if (BC_SIGNAL) {
    s = BC_STATUS_SIGNAL;
    goto err;
  }

  bc_num_copy(b, x0);
  scale -= 1;
  if (b->rdx > scale) bc_num_truncate(b, b->rdx - scale);

err:
  bc_num_free(&fprime);
  bc_num_free(&f);
  bc_num_free(&num2);
  bc_num_free(&num1);
  return s;
}

BcStatus bc_num_divmod(BcNum *a, BcNum *b, BcNum *c, BcNum *d, size_t scale) {

  BcStatus s;
  BcNum num2, *ptr_a;
  int init = 0;
  size_t ts = maxof(scale + b->rdx, a->rdx), len = bc_num_mulReq(a, b, ts);

  if (c == a) {
    memcpy(&num2, c, sizeof(BcNum));
    ptr_a = &num2;
    bc_num_init(c, len);
    init = 1;
  }
  else {
    ptr_a = a;
    bc_num_expand(c, len);
  }

  s = bc_num_r(ptr_a, b, c, d, scale, ts);

  if (init) bc_num_free(&num2);

  return s;
}

int bc_id_cmp(BcId *e1, BcId *e2) {
  return strcmp(e1->name, e2->name);
}

void bc_id_free(void *id) {
  free(((BcId*) id)->name);
}

void bc_string_free(void *string) {
  free(*((char**) string));
}

BcStatus bc_func_insert(BcFunc *f, char *name, BcType type, size_t line) {

  BcId a;
  size_t i;

  for (i = 0; i < f->autos.len; ++i) {
    BcId *id = bc_vec_item(&f->autos, i);
    if (!strcmp(name, id->name) && type == (BcType) id->idx)
      return bc_vm_error(BC_ERROR_PARSE_DUP_LOCAL, line, name);
  }

  a.idx = type;
  a.name = name;

  bc_vec_push(&f->autos, &a);

  return BC_STATUS_SUCCESS;
}

void bc_func_init(BcFunc *f, char *name) {
  bc_vec_init(&f->code, sizeof(uchar), NULL);
  bc_vec_init(&f->strs, sizeof(char*), bc_string_free);
  bc_vec_init(&f->consts, sizeof(char*), bc_string_free);
  bc_vec_init(&f->autos, sizeof(BcId), bc_id_free);
  bc_vec_init(&f->labels, sizeof(size_t), NULL);
  f->nparams = 0;
  f->voidfn = 0;
  f->name = name;
}

void bc_func_reset(BcFunc *f) {
  bc_vec_npop(&f->code, f->code.len);
  bc_vec_npop(&f->strs, f->strs.len);
  bc_vec_npop(&f->consts, f->consts.len);
  bc_vec_npop(&f->autos, f->autos.len);
  bc_vec_npop(&f->labels, f->labels.len);
  f->nparams = 0;
  f->voidfn = 0;
}

void bc_func_free(void *func) {
  BcFunc *f = (BcFunc*) func;
  bc_vec_free(&f->code);
  bc_vec_free(&f->strs);
  bc_vec_free(&f->consts);
  bc_vec_free(&f->autos);
  bc_vec_free(&f->labels);
}

void bc_array_init(BcVec *a, int nums) {
  if (nums) bc_vec_init(a, sizeof(BcNum), bc_num_free);
  else bc_vec_init(a, sizeof(BcVec), bc_vec_free);
  bc_array_expand(a, 1);
}

void bc_array_copy(BcVec *d, BcVec *s) {

  size_t i;

  bc_vec_npop(d, d->len);
  bc_vec_expand(d, s->cap);
  d->len = s->len;

  for (i = 0; i < s->len; ++i) {
    BcNum *dnum = bc_vec_item(d, i), *snum = bc_vec_item(s, i);
    bc_num_createCopy(dnum, snum);
  }
}

void bc_array_expand(BcVec *a, size_t len) {

  if (a->size == sizeof(BcNum) && a->dtor == bc_num_free) {
    BcNum n;
    while (len > a->len) {
      bc_num_init(&n, BC_NUM_DEF_SIZE);
      bc_vec_push(a, &n);
    }
  }
  else {
    BcVec v;
    while (len > a->len) {
      bc_array_init(&v, 1);
      bc_vec_push(a, &v);
    }
  }
}

void bc_result_free(void *result) {

  BcResult *r = (BcResult*) result;

  switch (r->t) {

    case BC_RESULT_TEMP:
    case BC_RESULT_IBASE:
    case BC_RESULT_SCALE:
    case BC_RESULT_OBASE:
    {
      bc_num_free(&r->d.n);
      break;
    }

    case BC_RESULT_VAR:
    case BC_RESULT_ARRAY:
    case BC_RESULT_ARRAY_ELEM:
    {
      free(r->d.id.name);
      break;
    }

    case BC_RESULT_STR:
    case BC_RESULT_CONSTANT:
    case BC_RESULT_VOID:
    case BC_RESULT_ONE:
    case BC_RESULT_LAST:
    {
      // Do nothing.
      break;
    }
  }
}

BcStatus bc_lex_invalidChar(BcLex *l, char c) {
  l->t = BC_LEX_INVALID;
  return bc_lex_verr(l, BC_ERROR_PARSE_CHAR, c);
}

void bc_lex_lineComment(BcLex *l) {
  l->t = BC_LEX_WHITESPACE;
  while (l->i < l->len && l->buf[l->i] != '\n') ++l->i;
}

BcStatus bc_lex_comment(BcLex *l) {

  size_t i, nlines = 0;
  char *buf = l->buf;
  int end = 0;
  char c;

  l->t = BC_LEX_WHITESPACE;

  for (i = ++l->i; !end; i += !end) {

    for (; (c = buf[i]) && c != '*'; ++i) nlines += (c == '\n');

    if (!c || buf[i + 1] == '\0') {
      l->i = i;
      return bc_lex_err(l, BC_ERROR_PARSE_COMMENT);
    }

    end = buf[i + 1] == '/';
  }

  l->i = i + 2;
  l->line += nlines;

  return BC_STATUS_SUCCESS;
}

void bc_lex_whitespace(BcLex *l) {
  char c;
  l->t = BC_LEX_WHITESPACE;
  for (c = l->buf[l->i]; c != '\n' && isspace(c); c = l->buf[++l->i]);
}

BcStatus bc_lex_number(BcLex *l, char start) {

  char *buf = l->buf + l->i;
  size_t i;
  char last_valid, c;
  int last_pt, pt = (start == '.');

  l->t = BC_LEX_NUMBER;
  last_valid = 'Z';

  bc_vec_npop(&l->str, l->str.len);
  bc_vec_push(&l->str, &start);

  for (i = 0; (c = buf[i]) && (BC_LEX_NUM_CHAR(c, last_valid, pt) ||
                               (c == '\\' && buf[i + 1] == '\n')); ++i)
  {
    if (c == '\\') {

      if (buf[i + 1] == '\n') {

        i += 2;

        // Make sure to eat whitespace at the beginning of the line.
        while(isspace(buf[i]) && buf[i] != '\n') ++i;

        c = buf[i];

        if (!BC_LEX_NUM_CHAR(c, last_valid, pt)) break;
      }
      else break;
    }

    last_pt = (c == '.');
    if (pt && last_pt) break;
    pt = pt || last_pt;

    bc_vec_push(&l->str, &c);
  }

  if (l->str.len - pt > BC_MAX_NUM)
    return bc_lex_verr(l, BC_ERROR_EXEC_NUM_LEN, BC_MAX_NUM);

  bc_vec_pushByte(&l->str, '\0');
  l->i += i;

  return BC_STATUS_SUCCESS;
}

BcStatus bc_lex_name(BcLex *l) {

  size_t i = 0;
  char *buf = l->buf + l->i - 1;
  char c = buf[i];

  l->t = BC_LEX_NAME;

  while ((c >= 'a' && c <= 'z') || isdigit(c) || c == '_') c = buf[++i];

  if (i > BC_MAX_NAME)
    return bc_lex_verr(l, BC_ERROR_EXEC_NAME_LEN, BC_MAX_NAME);

  bc_vec_string(&l->str, i, buf);

  // Increment the index. We minus 1 because it has already been incremented.
  l->i += i - 1;

  return BC_STATUS_SUCCESS;
}

void bc_lex_init(BcLex *l) {
  bc_vec_init(&l->str, sizeof(char), NULL);
}

void bc_lex_free(BcLex *l) {
  bc_vec_free(&l->str);
}

void bc_lex_file(BcLex *l, char *file) {
  l->line = 1;
  BC_VM->file = file;
}

BcStatus bc_lex_next(BcLex *l) {

  BcStatus s;

  l->last = l->t;
  l->line += (l->i != 0 && l->buf[l->i - 1] == '\n');

  if (l->last == BC_LEX_EOF) return bc_lex_err(l, BC_ERROR_PARSE_EOF);

  l->t = BC_LEX_EOF;

  if (l->i == l->len) return BC_STATUS_SUCCESS;

  // Loop until failure or we don't have whitespace. This
  // is so the parser doesn't get inundated with whitespace.
  do {
    s = bc_lex_token(l);
  } while (!s && l->t == BC_LEX_WHITESPACE);

  return s;
}

BcStatus bc_lex_text(BcLex *l, char *text) {
  l->buf = text;
  l->i = 0;
  l->len = strlen(text);
  l->t = l->last = BC_LEX_INVALID;
  return bc_lex_next(l);
}

static BcStatus bc_lex_identifier(BcLex *l) {

  BcStatus s;
  size_t i;
  char *buf = l->buf + l->i - 1;

  for (i = 0; i < bc_lex_kws_len; ++i) {

    BcLexKeyword *kw = bc_lex_kws + i;
    size_t len = BC_LEX_KW_LEN(kw);

    if (!strncmp(buf, kw->name, len) && !isalnum(buf[len]) && buf[len] != '_')
    {
      l->t = BC_LEX_KEY_AUTO + (BcLexType) i;

      if (!BC_LEX_KW_POSIX(kw)) {
        s = bc_lex_vposixErr(l, BC_ERROR_POSIX_KW, kw->name);
        if (s) return s;
      }

      // We minus 1 because the index has already been incremented.
      l->i += len - 1;
      return BC_STATUS_SUCCESS;
    }
  }

  s = bc_lex_name(l);
  if (s) return s;

  if (l->str.len - 1 > 1) s = bc_lex_vposixErr(l, BC_ERROR_POSIX_NAME_LEN, buf);

  return s;
}

static BcStatus bc_lex_string(BcLex *l) {

  size_t len, nlines = 0, i = l->i;
  char *buf = l->buf;
  char c;

  l->t = BC_LEX_STR;

  for (; (c = buf[i]) && c != '"'; ++i) nlines += c == '\n';

  if (c == '\0') {
    l->i = i;
    return bc_lex_err(l, BC_ERROR_PARSE_STRING);
  }

  len = i - l->i;

  if (len > BC_MAX_STRING)
    return bc_lex_verr(l, BC_ERROR_EXEC_STRING_LEN, BC_MAX_STRING);

  bc_vec_string(&l->str, len, l->buf + l->i);

  l->i = i + 1;
  l->line += nlines;

  return BC_STATUS_SUCCESS;
}

static void bc_lex_assign(BcLex *l, BcLexType with, BcLexType without) {
  if (l->buf[l->i] == '=') {
    ++l->i;
    l->t = with;
  }
  else l->t = without;
}

BcStatus bc_lex_token(BcLex *l) {

  BcStatus s = BC_STATUS_SUCCESS;
  char c = l->buf[l->i++], c2;

  // This is the workhorse of the lexer.
  switch (c) {

    case '\0':
    case '\n':
    {
      l->t = !c ? BC_LEX_EOF : BC_LEX_NLINE;
      break;
    }

    case '\t':
    case '\v':
    case '\f':
    case '\r':
    case ' ':
    {
      bc_lex_whitespace(l);
      break;
    }

    case '!':
    {
      bc_lex_assign(l, BC_LEX_OP_REL_NE, BC_LEX_OP_BOOL_NOT);

      if (l->t == BC_LEX_OP_BOOL_NOT) {
        s = bc_lex_vposixErr(l, BC_ERROR_POSIX_BOOL, "!");
        if (s) return s;
      }

      break;
    }

    case '"':
    {
      s = bc_lex_string(l);
      break;
    }

    case '#':
    {
      s = bc_lex_posixErr(l, BC_ERROR_POSIX_COMMENT);
      if (s) return s;

      bc_lex_lineComment(l);

      break;
    }

    case '%':
    {
      bc_lex_assign(l, BC_LEX_OP_ASSIGN_MODULUS, BC_LEX_OP_MODULUS);
      break;
    }

    case '&':
    {
      c2 = l->buf[l->i];
      if (c2 == '&') {

        s = bc_lex_vposixErr(l, BC_ERROR_POSIX_BOOL, "&&");
        if (s) return s;

        ++l->i;
        l->t = BC_LEX_OP_BOOL_AND;
      }
      else s = bc_lex_invalidChar(l, c);

      break;
    }
    case '(':
    case ')':
    {
      l->t = (BcLexType) (c - '(' + BC_LEX_LPAREN);
      break;
    }

    case '*':
    {
      bc_lex_assign(l, BC_LEX_OP_ASSIGN_MULTIPLY, BC_LEX_OP_MULTIPLY);
      break;
    }

    case '+':
    {
      c2 = l->buf[l->i];
      if (c2 == '+') {
        ++l->i;
        l->t = BC_LEX_OP_INC;
      }
      else bc_lex_assign(l, BC_LEX_OP_ASSIGN_PLUS, BC_LEX_OP_PLUS);
      break;
    }

    case ',':
    {
      l->t = BC_LEX_COMMA;
      break;
    }

    case '-':
    {
      c2 = l->buf[l->i];
      if (c2 == '-') {
        ++l->i;
        l->t = BC_LEX_OP_DEC;
      }
      else bc_lex_assign(l, BC_LEX_OP_ASSIGN_MINUS, BC_LEX_OP_MINUS);
      break;
    }

    case '.':
    {
      c2 = l->buf[l->i];
      if (BC_LEX_NUM_CHAR(c2, 'Z', 1)) s = bc_lex_number(l, c);
      else {
        l->t = BC_LEX_KEY_LAST;
        s = bc_lex_posixErr(l, BC_ERROR_POSIX_DOT);
      }
      break;
    }

    case '/':
    {
      c2 = l->buf[l->i];
      if (c2 =='*') s = bc_lex_comment(l);
      else bc_lex_assign(l, BC_LEX_OP_ASSIGN_DIVIDE, BC_LEX_OP_DIVIDE);
      break;
    }

    case '0':
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
    case 'A':
    case 'B':
    case 'C':
    case 'D':
    case 'E':
    case 'F':
    // Apparently, GNU bc (and maybe others) allows any uppercase letter as a
    // number. When single digits, they act like the ones above. When multi-
    // digit, any letter above the input base is automatically set to the
    // biggest allowable digit in the input base.
    case 'G':
    case 'H':
    case 'I':
    case 'J':
    case 'K':
    case 'L':
    case 'M':
    case 'N':
    case 'O':
    case 'P':
    case 'Q':
    case 'R':
    case 'S':
    case 'T':
    case 'U':
    case 'V':
    case 'W':
    case 'X':
    case 'Y':
    case 'Z':
    {
      s = bc_lex_number(l, c);
      break;
    }

    case ';':
    {
      l->t = BC_LEX_SCOLON;
      break;
    }

    case '<':
    {
      bc_lex_assign(l, BC_LEX_OP_REL_LE, BC_LEX_OP_REL_LT);
      break;
    }

    case '=':
    {
      bc_lex_assign(l, BC_LEX_OP_REL_EQ, BC_LEX_OP_ASSIGN);
      break;