path: root/Src/math.c

/*
 * math.c - mathematical expression evaluation
 *
 * This file is part of zsh, the Z shell.
 *
 * Copyright (c) 1992-1997 Paul Falstad
 * All rights reserved.
 *
 * Permission is hereby granted, without written agreement and without
 * license or royalty fees, to use, copy, modify, and distribute this
 * software and to distribute modified versions of this software for any
 * purpose, provided that the above copyright notice and the following
 * two paragraphs appear in all copies of this software.
 *
 * In no event shall Paul Falstad or the Zsh Development Group be liable
 * to any party for direct, indirect, special, incidental, or consequential
 * damages arising out of the use of this software and its documentation,
 * even if Paul Falstad and the Zsh Development Group have been advised of
 * the possibility of such damage.
 *
 * Paul Falstad and the Zsh Development Group specifically disclaim any
 * warranties, including, but not limited to, the implied warranties of
 * merchantability and fitness for a particular purpose.  The software
 * provided hereunder is on an "as is" basis, and Paul Falstad and the
 * Zsh Development Group have no obligation to provide maintenance,
 * support, updates, enhancements, or modifications.
 *
 */

#include "zsh.mdh"
#include "math.pro"

#include <math.h>

/* nonzero means we are not evaluating, just parsing */
 
/**/
int noeval;
 
/* integer zero */

/**/
mnumber zero_mnumber;

/* last input base we used */

/**/
int lastbase;
 
static char *ptr;

static mnumber yyval;
static char *yylval;

#define MAX_MLEVEL 256

static int mlevel = 0;

/* != 0 means recognize unary plus, minus, etc. */

static int unary = 1;

/* LR = left-to-right associativity *
 * RL = right-to-left associativity *
 * BOOL = short-circuiting boolean   */

#define LR   0x0000
#define RL   0x0001
#define BOOL 0x0002

#define MTYPE(x)  ((x) & 3)

/*
 * OP_A2    2 arguments
 * OP_A2IR  2 arguments, return integer
 * OP_A2IO  2 arguments, must be integer, return integer
 * OP_E2    2 arguments with assignment
 * OP_E2IO  2 arguments with assignment, must be integer, return integer
 * OP_OP    None of the above, but occurs where we are expecting an operator
 *          rather than an operand.
 * OP_OPF   Followed by an operator, not an operand.
 *
 * OP_A2*, OP_E2*, OP_OP*:
 *   Occur when we need an operator; the next object must be an operand,
 *   unless OP_OPF is also supplied.
 *
 * Others:
 *   Occur when we need an operand; the next object must also be an operand,
 *   unless OP_OPF is also supplied.
 */
#define OP_A2   0x0004
#define OP_A2IR 0x0008
#define OP_A2IO 0x0010
#define OP_E2   0x0020
#define OP_E2IO 0x0040
#define OP_OP   0x0080
#define OP_OPF  0x0100

#define M_INPAR 0
#define M_OUTPAR 1
#define NOT 2
#define COMP 3
#define POSTPLUS 4
#define POSTMINUS 5
#define UPLUS 6
#define UMINUS 7
#define AND 8
#define XOR 9
#define OR 10
#define MUL 11
#define DIV 12
#define MOD 13
#define PLUS 14
#define MINUS 15
#define SHLEFT 16
#define SHRIGHT 17
#define LES 18
#define LEQ 19
#define GRE 20
#define GEQ 21
#define DEQ 22
#define NEQ 23
#define DAND 24
#define DOR 25
#define DXOR 26
#define QUEST 27
#define COLON 28
#define EQ 29
#define PLUSEQ 30
#define MINUSEQ 31
#define MULEQ 32
#define DIVEQ 33
#define MODEQ 34
#define ANDEQ 35
#define XOREQ 36
#define OREQ 37
#define SHLEFTEQ 38
#define SHRIGHTEQ 39
#define DANDEQ 40
#define DOREQ 41
#define DXOREQ 42
#define COMMA 43
#define EOI 44
#define PREPLUS 45
#define PREMINUS 46
#define NUM 47
#define ID 48
#define POWER 49
#define CID 50
#define POWEREQ 51
#define FUNC 52
#define TOKCOUNT 53

/* precedences */

static int prec[TOKCOUNT] =
{
     1, 137,  2,  2,   2,
     2,   2,  2,  4,   5,
     6,   8,  8,  8,   9,
     9,   3,  3, 10,  10,
    10,  10, 11, 11,  12,
    13,  13, 14, 15,  16,
    16,  16, 16, 16,  16,
    16,  16, 16, 16,  16,
    16,  16, 16, 17, 200,
     2,   2,  0,  0,   7,
     0,  16, 0
};

#define TOPPREC 17
#define ARGPREC (TOPPREC-1)

static int type[TOKCOUNT] =
{
/*  0 */  LR, LR|OP_OP|OP_OPF, RL, RL, RL|OP_OP|OP_OPF,
/*  5 */  RL|OP_OP|OP_OPF, RL, RL, LR|OP_A2IO, LR|OP_A2IO,
/* 10 */  LR|OP_A2IO, LR|OP_A2, LR|OP_A2, LR|OP_A2IO, LR|OP_A2,
/* 15 */  LR|OP_A2, LR|OP_A2IO, LR|OP_A2IO, LR|OP_A2IR, LR|OP_A2IR,
/* 20 */  LR|OP_A2IR, LR|OP_A2IR, LR|OP_A2IR, LR|OP_A2IR, BOOL|OP_A2IO,
/* 25 */  BOOL|OP_A2IO, LR|OP_A2IO, RL|OP_OP, RL|OP_OP, RL|OP_E2,
/* 30 */  RL|OP_E2, RL|OP_E2, RL|OP_E2, RL|OP_E2, RL|OP_E2IO,
/* 35 */  RL|OP_E2IO, RL|OP_E2IO, RL|OP_E2IO, RL|OP_E2IO, RL|OP_E2IO,
/* 40 */  BOOL|OP_E2IO, BOOL|OP_E2IO, RL|OP_A2IO, RL|OP_A2, RL|OP_OP,
/* 45 */  RL, RL, LR|OP_OPF, LR|OP_OPF, RL|OP_A2,
/* 50 */  LR|OP_OPF, RL|OP_E2, LR|OP_OPF
};

/**/
int outputradix;

/**/
static int
zzlex(void)
{
#ifdef USE_LOCALE
    char *prev_locale;
#endif
    int cct = 0;
    yyval.type = MN_INTEGER;

    for (;; cct = 0)
	switch (*ptr++) {
	case '+':
	    if (*ptr == '+' && (unary || !ialnum(*ptr))) {
		ptr++;
		return (unary) ? PREPLUS : POSTPLUS;
	    }
	    if (*ptr == '=') {
		ptr++;
		return PLUSEQ;
	    }
	    return (unary) ? UPLUS : PLUS;
	case '-':
	    if (*ptr == '-' && (unary || !ialnum(*ptr))) {
		ptr++;
		return (unary) ? PREMINUS : POSTMINUS;
	    }
	    if (*ptr == '=') {
		ptr++;
		return MINUSEQ;
	    }
	    return (unary) ? UMINUS : MINUS;
	case '(':
	    return M_INPAR;
	case ')':
	    return M_OUTPAR;
	case '!':
	    if (*ptr == '=') {
		ptr++;
		return NEQ;
	    }
	    return NOT;
	case '~':
	    return COMP;
	case '&':
	    if (*ptr == '&') {
		if (*++ptr == '=') {
		    ptr++;
		    return DANDEQ;
		}
		return DAND;
	    } else if (*ptr == '=') {
		ptr++;
		return ANDEQ;
	    }
	    return AND;
	case '|':
	    if (*ptr == '|') {
		if (*++ptr == '=') {
		    ptr++;
		    return DOREQ;
		}
		return DOR;
	    } else if (*ptr == '=') {
		ptr++;
		return OREQ;
	    }
	    return OR;
	case '^':
	    if (*ptr == '^') {
		if (*++ptr == '=') {
		    ptr++;
		    return DXOREQ;
		}
		return DXOR;
	    } else if (*ptr == '=') {
		ptr++;
		return XOREQ;
	    }
	    return XOR;
	case '*':
	    if (*ptr == '*') {
		if (*++ptr == '=') {
		    ptr++;
		    return POWEREQ;
		}
		return POWER;
	    }
	    if (*ptr == '=') {
		ptr++;
		return MULEQ;
	    }
	    return MUL;
	case '/':
	    if (*ptr == '=') {
		ptr++;
		return DIVEQ;
	    }
	    return DIV;
	case '%':
	    if (*ptr == '=') {
		ptr++;
		return MODEQ;
	    }
	    return MOD;
	case '<':
	    if (*ptr == '<') {
		if (*++ptr == '=') {
		    ptr++;
		    return SHLEFTEQ;
		}
		return SHLEFT;
	    } else if (*ptr == '=') {
		ptr++;
		return LEQ;
	    }
	    return LES;
	case '>':
	    if (*ptr == '>') {
		if (*++ptr == '=') {
		    ptr++;
		    return SHRIGHTEQ;
		}
		return SHRIGHT;
	    } else if (*ptr == '=') {
		ptr++;
		return GEQ;
	    }
	    return GRE;
	case '=':
	    if (*ptr == '=') {
		ptr++;
		return DEQ;
	    }
	    return EQ;
	case '$':
	    yyval.u.l = mypid;
	    return NUM;
	case '?':
	    if (unary) {
		yyval.u.l = lastval;
		return NUM;
	    }
	    return QUEST;
	case ':':
	    return COLON;
	case ',':
	    return COMMA;
	case '\0':
	    ptr--;
	    return EOI;
	case '[':
	    {
		int n;

		if (idigit(*ptr)) {
		    n = zstrtol(ptr, &ptr, 10);
		    if (*ptr != ']' || !idigit(*++ptr)) {
			zerr("bad base syntax", NULL, 0);
			return EOI;
		    }
		    yyval.u.l = zstrtol(ptr, &ptr, lastbase = n);
		    return NUM;
		}
		if (*ptr == '#') {
		    n = 1;
		    if (*++ptr == '#') {
			n = -1;
			ptr++;
		    }
		    if (!idigit(*ptr))
			goto bofs;
		    outputradix = n * zstrtol(ptr, &ptr, 10);
		} else {
		    bofs:
		    zerr("bad output format specification", NULL, 0);
		    return EOI;
		}
		if(*ptr != ']')
			goto bofs;
		ptr++;
		break;
	    }
	case ' ':
	case '\t':
	case '\n':
	    break;
	case '0':
	    if (*ptr == 'x' || *ptr == 'X') {
		/* Should we set lastbase here? */
		yyval.u.l = zstrtol(++ptr, &ptr, lastbase = 16);
		return NUM;
	    }
	    else if (isset(OCTALZEROES) &&
		    (memchr(ptr, '.', strlen(ptr)) == NULL) &&
		     idigit(*ptr)) {
	        yyval.u.l = zstrtol(ptr, &ptr, lastbase = 8);
		return NUM;
	    }
	/* Fall through! */
	default:
	    if (idigit(*--ptr) || *ptr == '.') {
		char *nptr;
		for (nptr = ptr; idigit(*nptr); nptr++);

		if (*nptr == '.' || *nptr == 'e' || *nptr == 'E') {
		    /* it's a float */
		    yyval.type = MN_FLOAT;
#ifdef USE_LOCALE
		    prev_locale = setlocale(LC_NUMERIC, NULL);
		    setlocale(LC_NUMERIC, "POSIX");
#endif
		    yyval.u.d = strtod(ptr, &nptr);
#ifdef USE_LOCALE
		    setlocale(LC_NUMERIC, prev_locale);
#endif
		    if (ptr == nptr || *nptr == '.') {
			zerr("bad floating point constant", NULL, 0);
			return EOI;
		    }
		    ptr = nptr;
		} else {
		    /* it's an integer */
		    yyval.u.l = zstrtol(ptr, &ptr, 10);

		    if (*ptr == '#') {
			ptr++;
			yyval.u.l = zstrtol(ptr, &ptr, lastbase = yyval.u.l);
		    }
		}
		return NUM;
	    }
	    if (*ptr == '#') {
		if (*++ptr == '\\' || *ptr == '#') {
		    int v;

		    ptr++;
		    ptr = getkeystring(ptr, NULL, 6, &v);
		    yyval.u.l = v;
		    return NUM;
		}
		cct = 1;
	    }
	    if (iident(*ptr)) {
		int func = 0;
		char *p;

		p = ptr;
		while (iident(*++ptr));
		if (*ptr == '[' || (!cct && *ptr == '(')) {
		    char op = *ptr, cp = ((*ptr == '[') ? ']' : ')');
		    int l;
		    func = (op == '(');
		    for (ptr++, l = 1; *ptr && l; ptr++) {
			if (*ptr == op)
			    l++;
			if (*ptr == cp)
			    l--;
			if (*ptr == '\\' && ptr[1])
			    ptr++;
		    }
		}
		yylval = dupstrpfx(p, ptr - p);
		return (func ? FUNC : (cct ? CID : ID));
	    }
	    else if (cct) {
		yyval.u.l = poundgetfn(NULL);
		return NUM;
	    }
	    return EOI;
	}
}

/* the value stack */

#define STACKSZ 100
static int mtok;			/* last token */
static int sp = -1;			/* stack pointer */

struct mathvalue {
    char *lval;
    mnumber val;
};

static struct mathvalue *stack;

/**/
static void
push(mnumber val, char *lval)
{
    if (sp == STACKSZ - 1)
	zerr("stack overflow", NULL, 0);
    else
	sp++;
    stack[sp].val = val;
    stack[sp].lval = lval;
}


/**/
static mnumber
getcvar(char *s)
{
    char *t;
    mnumber mn;
    mn.type = MN_INTEGER;

    queue_signals();
    if (!(t = getsparam(s)))
	mn.u.l = 0;
    else
        mn.u.l = STOUC(*t == Meta ? t[1] ^ 32 : *t);
    unqueue_signals();
    return mn;
}


/**/
static mnumber
setvar(char *s, mnumber v)
{
    if (!s) {
	zerr("lvalue required", NULL, 0);
	v.type = MN_INTEGER;
	v.u.l = 0;
	return v;
    }
    if (noeval)
	return v;
    untokenize(s);
    setnparam(s, v);
    return v;
}


/**/
static mnumber
callmathfunc(char *o)
{
    MathFunc f;
    char *a, *n;
    static mnumber dummy;

    n = a = dupstring(o);

    while (*a != '(')
	a++;
    *a++ = '\0';
    a[strlen(a) - 1] = '\0';

    if ((f = getmathfunc(n, 1))) {
	if (f->flags & MFF_STR)
	    return f->sfunc(n, a, f->funcid);
	else {
	    int argc = 0;
	    mnumber *argv = NULL, *q;
	    LinkList l = newlinklist();
	    LinkNode node;

	    while (iblank(*a))
		a++;
	    while (*a) {
		if (*a) {
		    argc++;
 		    q = (mnumber *) zhalloc(sizeof(mnumber));
		    *q = mathevall(a, ARGPREC, &a);
		    addlinknode(l, q);
		    if (errflag || mtok != COMMA)
			break;
		}
	    }
	    if (*a && !errflag)
		zerr("bad math expression: illegal character: %c",
		     NULL, *a);
	    if (!errflag) {
		if (argc >= f->minargs && (f->maxargs < 0 ||
					   argc <= f->maxargs)) {
		    if (argc) {
			q = argv = (mnumber *)zhalloc(argc * sizeof(mnumber));
			for (node = firstnode(l); node; incnode(node))
			    *q++ = *(mnumber *)getdata(node);
		    }
		    return f->nfunc(n, argc, argv, f->funcid);
		} else
		    zerr("wrong number of arguments: %s", o, 0);
	    }
	}
    } else
	zerr("unknown function: %s", n, 0);

    dummy.type = MN_INTEGER;
    dummy.u.l = 0;

    return dummy;
}

/**/
static int
notzero(mnumber a)
{
    if ((a.type & MN_INTEGER) ? a.u.l == 0 : a.u.d == 0.0) {
	zerr("division by zero", NULL, 0);
	return 0;
    }
    return 1;
}

/* macro to pop three values off the value stack */

/**/
void
op(int what)
{
    mnumber a, b, c, *spval;
    char *lv;
    int tp = type[what];

    if (errflag)
	return;
    if (sp < 0) {
	zerr("bad math expression: stack empty", NULL, 0);
	return;
    }

    if (tp & (OP_A2|OP_A2IR|OP_A2IO|OP_E2|OP_E2IO)) {
	/* Make sure anyone seeing this message reports it. */
	DPUTS(sp < 1, "BUG: math: not enough wallabies in outback.");
	b = stack[sp--].val;
	a = stack[sp--].val;

	if (tp & (OP_A2IO|OP_E2IO)) {
	    /* coerce to integers */
	    if (a.type & MN_FLOAT) {
		a.type = MN_INTEGER;
		a.u.l = (zlong)a.u.d;
	    }
	    if (b.type & MN_FLOAT) {
		b.type = MN_INTEGER;
		b.u.l = (zlong)b.u.d;
	    }
	} else if (a.type != b.type && what != COMMA) {
	    /*
	     * Different types, so coerce to float.
	     * It may happen during an assigment that the LHS
	     * variable is actually an integer, but there's still
	     * no harm in doing the arithmetic in floating point;
	     * the assignment will do the correct conversion.
	     * This way, if the parameter is actually a scalar, but
	     * used to contain an integer, we can write a float into it.
	     */
	    if (a.type & MN_INTEGER) {
		a.type = MN_FLOAT;
		a.u.d = (double)a.u.l;
	    }
	    if (b.type & MN_INTEGER) {
		b.type = MN_FLOAT;
		b.u.d = (double)b.u.l;
	    }
	}

	if (noeval) {
	    c.type = MN_INTEGER;
	    c.u.l = 0;
	} else {
	    /*
	     * type for operation: usually same as operands, but e.g.
	     * (a == b) returns int.
	     */
	    c.type = (tp & OP_A2IR) ? MN_INTEGER : a.type;

	    switch(what) {
	    case AND:
	    case ANDEQ:
		c.u.l = a.u.l & b.u.l;
		break;
	    case XOR:
	    case XOREQ:
		c.u.l = a.u.l ^ b.u.l;
		break;
	    case OR:
	    case OREQ:
		c.u.l = a.u.l | b.u.l;
		break;
	    case MUL:
	    case MULEQ:
		if (c.type == MN_FLOAT)
		    c.u.d = a.u.d * b.u.d;
		else
		    c.u.l = a.u.l * b.u.l;
		break;
	    case DIV:
	    case DIVEQ:
		if (!notzero(b))
		    return;
		if (c.type == MN_FLOAT)
		    c.u.d = a.u.d / b.u.d;
		else
		    c.u.l = a.u.l / b.u.l;
		break;
	    case MOD:
	    case MODEQ:
		if (!notzero(b))
		    return;
		c.u.l = a.u.l % b.u.l;
		break;
	    case PLUS:
	    case PLUSEQ:
		if (c.type == MN_FLOAT)
		    c.u.d = a.u.d + b.u.d;
		else
		    c.u.l = a.u.l + b.u.l;
		break;
	    case MINUS:
	    case MINUSEQ:
		if (c.type == MN_FLOAT)
		    c.u.d = a.u.d - b.u.d;
		else
		    c.u.l = a.u.l - b.u.l;
		break;
	    case SHLEFT:
	    case SHLEFTEQ:
		c.u.l = a.u.l << b.u.l;
		break;
	    case SHRIGHT:
	    case SHRIGHTEQ:
		c.u.l = a.u.l >> b.u.l;
		break;
	    case LES:
		c.u.l = (zlong)
		    (a.type == MN_FLOAT ? (a.u.d < b.u.d) : (a.u.l < b.u.l));
		break;
	    case LEQ:
		c.u.l = (zlong)
		    (a.type == MN_FLOAT ? (a.u.d <= b.u.d) : (a.u.l <= b.u.l));
		break;
	    case GRE:
		c.u.l = (zlong)
		    (a.type == MN_FLOAT ? (a.u.d > b.u.d) : (a.u.l > b.u.l));
		break;
	    case GEQ:
		c.u.l = (zlong)
		    (a.type == MN_FLOAT ? (a.u.d >= b.u.d) : (a.u.l >= b.u.l));
		break;
	    case DEQ:
		c.u.l = (zlong)
		    (a.type == MN_FLOAT ? (a.u.d == b.u.d) : (a.u.l == b.u.l));
		break;
	    case NEQ:
		c.u.l = (zlong)
		    (a.type == MN_FLOAT ? (a.u.d != b.u.d) : (a.u.l != b.u.l));
		break;
	    case DAND:
	    case DANDEQ:
		c.u.l = (zlong)(a.u.l && b.u.l);
		break;
	    case DOR:
	    case DOREQ:
		c.u.l = (zlong)(a.u.l || b.u.l);
		break;
	    case DXOR:
	    case DXOREQ:
		c.u.l = (zlong)((a.u.l && !b.u.l) || (!a.u.l && b.u.l));
		break;
	    case COMMA:
		c = b;
		break;
	    case POWER:
	    case POWEREQ:
		if (c.type == MN_INTEGER && b.u.l < 0) {
		    /* produces a real result, so cast to real. */
		    a.type = b.type = c.type = MN_FLOAT;
		    a.u.d = (double) a.u.l;
		    b.u.d = (double) b.u.l;
		}
		if (c.type == MN_INTEGER) {
		    for (c.u.l = 1; b.u.l--; c.u.l *= a.u.l);
		} else {
		    if (b.u.d <= 0 && !notzero(a))
			return;
		    if (a.u.d < 0) {
			/* Error if (-num ** b) and b is not an integer */
			double tst = (double)(zlong)b.u.d;
			if (tst != b.u.d) {
			    zerr("imaginary power", NULL, 0);
			    return;
			}
		    }
		    c.u.d = pow(a.u.d, b.u.d);
		}
		break;
	    case EQ:
		c = b;
		break;
	    }
	}
	if (tp & (OP_E2|OP_E2IO)) {
	    lv = stack[sp+1].lval;
	    push(setvar(lv,c), lv);
	} else
	    push(c,NULL);
	return;
    }

    spval = &stack[sp].val;
    switch (what) {
    case NOT:
	if (spval->type & MN_FLOAT) {
	    spval->u.l = !spval->u.d;
	    spval->type = MN_INTEGER;
	} else
	    spval->u.l = !spval->u.l;
	stack[sp].lval = NULL;
	break;
    case COMP:
	if (spval->type & MN_FLOAT) {
	    spval->u.l = ~((zlong)spval->u.d);
	    spval->type = MN_INTEGER;
	} else
	    spval->u.l = ~spval->u.l;
	stack[sp].lval = NULL;
	break;
    case POSTPLUS:
	a = *spval;
	if (spval->type & MN_FLOAT)
	    a.u.d++;
	else
	    a.u.l++;
	(void)setvar(stack[sp].lval, a);
	break;
    case POSTMINUS:
	a = *spval;
	if (spval->type & MN_FLOAT)
	    a.u.d--;
	else
	    a.u.l--;
	(void)setvar(stack[sp].lval, a);
	break;
    case UPLUS:
	stack[sp].lval = NULL;
	break;
    case UMINUS:
	if (spval->type & MN_FLOAT)
	    spval->u.d = -spval->u.d;
	else
	    spval->u.l = -spval->u.l;
	stack[sp].lval = NULL;
	break;
    case QUEST:
	DPUTS(sp < 2, "BUG: math: three shall be the number of the counting.");
	c = stack[sp--].val;
	b = stack[sp--].val;
	a = stack[sp--].val;
	/* b and c can stay different types in this case. */
	push(((a.type & MN_FLOAT) ? a.u.d : a.u.l) ? b : c, NULL);
	break;
    case COLON:
	zerr("':' without '?'", NULL, 0);
	break;
    case PREPLUS:
	if (spval->type & MN_FLOAT)
	    spval->u.d++;
	else
	    spval->u.l++;
	setvar(stack[sp].lval, *spval);
	break;
    case PREMINUS:
	if (spval->type & MN_FLOAT)
	    spval->u.d--;
	else
	    spval->u.l--;
	setvar(stack[sp].lval, *spval);
	break;
    default:
	zerr("out of integers", NULL, 0);
	return;
    }
}


/**/
static void
bop(int tk)
{
    mnumber *spval = &stack[sp].val;
    int tst = (spval->type & MN_FLOAT) ? (zlong)spval->u.d : spval->u.l; 

    switch (tk) {
    case DAND:
    case DANDEQ:
	if (!tst)
	    noeval++;
	break;
    case DOR:
    case DOREQ:
	if (tst)
	    noeval++;
	break;
    };
}


/**/
static mnumber
mathevall(char *s, int prek, char **ep)
{
    int xlastbase, xnoeval, xunary;
    char *xptr;
    mnumber xyyval;
    char *xyylval;
    int xsp;
    struct mathvalue *xstack = 0, nstack[STACKSZ];
    mnumber ret;

    if (mlevel >= MAX_MLEVEL) {
	xyyval.type = MN_INTEGER;
	xyyval.u.l = 0;

	zerr("math recursion limit exceeded", NULL, 0);

	return xyyval;
    }
    if (mlevel++) {
	xlastbase = lastbase;
	xnoeval = noeval;
	xunary = unary;
	xptr = ptr;
	xyyval = yyval;
	xyylval = yylval;

	xsp = sp;
	xstack = stack;
    } else {
	xlastbase = xnoeval = xunary = xsp = 0;
	xyyval.type = MN_INTEGER;
	xyyval.u.l = 0;
	xyylval = NULL;
	xptr = NULL;
    }
    stack = nstack;
    lastbase = -1;
    ptr = s;
    sp = -1;
    unary = 1;
    stack[0].val.type = MN_INTEGER;
    stack[0].val.u.l = 0;
    mathparse(prek);
    *ep = ptr;
    DPUTS(!errflag && sp,
	  "BUG: math: wallabies roaming too freely in outback");

    ret = stack[0].val;

    if (--mlevel) {
	lastbase = xlastbase;
	noeval = xnoeval;
	unary = xunary;
	ptr = xptr;
	yyval = xyyval;
	yylval = xyylval;

	sp = xsp;
	stack = xstack;
    }
    return ret;
}


/**/
mod_export mnumber
matheval(char *s)
{
    char *junk;
    mnumber x;
    int xmtok = mtok;
    /* maintain outputradix across levels of evaluation */
    if (!mlevel)
	outputradix = 0;

    if (!*s) {
	x.type = MN_INTEGER;
	x.u.l = 0;
	return x;
    }
    x = mathevall(s, TOPPREC, &junk);
    mtok = xmtok;
    if (*junk)
	zerr("bad math expression: illegal character: %c", NULL, *junk);
    return x;
}

/**/
mod_export zlong
mathevali(char *s)
{
    mnumber x = matheval(s);
    return (x.type & MN_FLOAT) ? (zlong)x.u.d : x.u.l;
}


/**/
zlong
mathevalarg(char *s, char **ss)
{
    mnumber x;
    int xmtok = mtok;

    x = mathevall(s, ARGPREC, ss);
    if (mtok == COMMA)
	(*ss)--;
    mtok = xmtok;
    return (x.type & MN_FLOAT) ? (zlong)x.u.d : x.u.l;
}

/*
 * Make sure we have an operator or an operand, whatever is expected.
 * For this purpose, unary operators constitute part of an operand.
 */

/**/
static void
checkunary(int mtokc, char *mptr)
{
    int errmsg = 0;
    int tp = type[mtokc];
    if (tp & (OP_A2|OP_A2IR|OP_A2IO|OP_E2|OP_E2IO|OP_OP)) {
	if (unary)
	    errmsg = 1;
    } else {
	if (!unary)
	    errmsg = 2;
    }
    if (errmsg) {
	char errbuf[80];
	int len, over = 0;
	while (inblank(*mptr))
	    mptr++;
	len = ztrlen(mptr);
	if (len > 10) {
	    len = 10;
	    over = 1;
	}
	sprintf(errbuf, "bad math expression: %s expected at `%%l%s'",
		errmsg == 2 ? "operator" : "operand",
		over ? "..." : ""); 
	zerr(errbuf, mptr, len);
    }
    unary = !(tp & OP_OPF);
}

/* operator-precedence parse the string and execute */

/**/
static void
mathparse(int pc)
{
    zlong q;
    int otok, onoeval;
    char *optr = ptr;

    if (errflag)
	return;
    mtok = zzlex();
    checkunary(mtok, optr);
    while (prec[mtok] <= pc) {
	if (errflag)
	    return;
	switch (mtok) {
	case NUM:
	    push(yyval, NULL);
	    break;
	case ID:
	    push((noeval ? zero_mnumber : getnparam(yylval)), yylval);
	    break;
	case CID:
	    push((noeval ? zero_mnumber : getcvar(yylval)), yylval);
	    break;
	case FUNC:
	    push((noeval ? zero_mnumber : callmathfunc(yylval)), yylval);
	    break;
	case M_INPAR:
	    mathparse(TOPPREC);
	    if (mtok != M_OUTPAR) {
		if (!errflag)
		    zerr("')' expected", NULL, 0);
		return;
	    }
	    break;
	case QUEST:
	    q = (stack[sp].val.type == MN_FLOAT) ? (zlong)stack[sp].val.u.d :
		stack[sp].val.u.l;

	    if (!q)
		noeval++;
	    mathparse(prec[COLON] - 1);
	    if (!q)
		noeval--;
	    if (mtok != COLON) {
		if (!errflag)
		    zerr("':' expected", NULL, 0);
		return;
	    }
	    if (q)
		noeval++;
	    mathparse(prec[QUEST]);
	    if (q)
		noeval--;
	    op(QUEST);
	    continue;
	default:
	    otok = mtok;
	    onoeval = noeval;
	    if (MTYPE(type[otok]) == BOOL)
		bop(otok);
	    mathparse(prec[otok] - (MTYPE(type[otok]) != RL));
	    noeval = onoeval;
	    op(otok);
	    continue;
	}
	optr = ptr;
	mtok = zzlex();
	checkunary(mtok, optr);
    }
}