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expr.c revision 1.6
      1  1.5    glass /*
      2  1.5    glass  * Copyright (c) 1989, 1993
      3  1.5    glass  *	The Regents of the University of California.  All rights reserved.
      4  1.5    glass  *
      5  1.5    glass  * This code is derived from software contributed to Berkeley by
      6  1.5    glass  * Ozan Yigit at York University.
      7  1.5    glass  *
      8  1.5    glass  * Redistribution and use in source and binary forms, with or without
      9  1.5    glass  * modification, are permitted provided that the following conditions
     10  1.5    glass  * are met:
     11  1.5    glass  * 1. Redistributions of source code must retain the above copyright
     12  1.5    glass  *    notice, this list of conditions and the following disclaimer.
     13  1.5    glass  * 2. Redistributions in binary form must reproduce the above copyright
     14  1.5    glass  *    notice, this list of conditions and the following disclaimer in the
     15  1.5    glass  *    documentation and/or other materials provided with the distribution.
     16  1.5    glass  * 3. All advertising materials mentioning features or use of this software
     17  1.5    glass  *    must display the following acknowledgement:
     18  1.5    glass  *	This product includes software developed by the University of
     19  1.5    glass  *	California, Berkeley and its contributors.
     20  1.5    glass  * 4. Neither the name of the University nor the names of its contributors
     21  1.5    glass  *    may be used to endorse or promote products derived from this software
     22  1.5    glass  *    without specific prior written permission.
     23  1.5    glass  *
     24  1.5    glass  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     25  1.5    glass  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     26  1.5    glass  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     27  1.5    glass  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     28  1.5    glass  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     29  1.5    glass  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     30  1.5    glass  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     31  1.5    glass  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     32  1.5    glass  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     33  1.5    glass  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     34  1.5    glass  * SUCH DAMAGE.
     35  1.5    glass  */
     36  1.5    glass 
     37  1.5    glass #ifndef lint
     38  1.5    glass static char sccsid[] = "@(#)expr.c	8.1 (Berkeley) 6/6/93";
     39  1.5    glass #endif /* not lint */
     40  1.2    glass 
     41  1.5    glass #include <sys/cdefs.h>
     42  1.5    glass #include <stdio.h>
     43  1.5    glass 
     44  1.5    glass /*
     45  1.5    glass  *      expression evaluator: performs a standard recursive
     46  1.5    glass  *      descent parse to evaluate any expression permissible
     47  1.5    glass  *      within the following grammar:
     48  1.5    glass  *
     49  1.5    glass  *      expr    :       query EOS
     50  1.5    glass  *      query   :       lor
     51  1.5    glass  *              |       lor "?" query ":" query
     52  1.5    glass  *      lor     :       land { "||" land }
     53  1.6  mycroft  *      land    :       not { "&&" not }
     54  1.6  mycroft  *	not	:	eqrel
     55  1.6  mycroft  *		|	'!' not
     56  1.6  mycroft  *      eqrel   :       shift { eqrelop shift }
     57  1.5    glass  *      shift   :       primary { shop primary }
     58  1.5    glass  *      primary :       term { addop term }
     59  1.6  mycroft  *      term    :       exp { mulop exp }
     60  1.6  mycroft  *	exp	:	unary { expop unary }
     61  1.5    glass  *      unary   :       factor
     62  1.5    glass  *              |       unop unary
     63  1.5    glass  *      factor  :       constant
     64  1.5    glass  *              |       "(" query ")"
     65  1.5    glass  *      constant:       num
     66  1.5    glass  *              |       "'" CHAR "'"
     67  1.5    glass  *      num     :       DIGIT
     68  1.5    glass  *              |       DIGIT num
     69  1.5    glass  *      shop    :       "<<"
     70  1.5    glass  *              |       ">>"
     71  1.6  mycroft  *      eqrel   :       "="
     72  1.5    glass  *              |       "=="
     73  1.5    glass  *              |       "!="
     74  1.6  mycroft  *      	|       "<"
     75  1.5    glass  *              |       ">"
     76  1.5    glass  *              |       "<="
     77  1.5    glass  *              |       ">="
     78  1.5    glass  *
     79  1.5    glass  *
     80  1.5    glass  *      This expression evaluator is lifted from a public-domain
     81  1.5    glass  *      C Pre-Processor included with the DECUS C Compiler distribution.
     82  1.5    glass  *      It is hacked somewhat to be suitable for m4.
     83  1.5    glass  *
     84  1.5    glass  *      Originally by:  Mike Lutz
     85  1.5    glass  *                      Bob Harper
     86  1.5    glass  */
     87  1.5    glass 
     88  1.5    glass #define TRUE    1
     89  1.2    glass #define FALSE   0
     90  1.5    glass #define EOS     (char) 0
     91  1.5    glass #define EQL     0
     92  1.5    glass #define NEQ     1
     93  1.5    glass #define LSS     2
     94  1.5    glass #define LEQ     3
     95  1.5    glass #define GTR     4
     96  1.5    glass #define GEQ     5
     97  1.5    glass #define OCTAL   8
     98  1.5    glass #define DECIMAL 10
     99  1.5    glass 
    100  1.5    glass static char *nxtch;		       /* Parser scan pointer */
    101  1.5    glass 
    102  1.5    glass static int query __P((void));
    103  1.5    glass static int lor __P((void));
    104  1.5    glass static int land __P((void));
    105  1.6  mycroft static int not __P((void));
    106  1.6  mycroft static int eqrel __P((void));
    107  1.5    glass static int shift __P((void));
    108  1.5    glass static int primary __P((void));
    109  1.5    glass static int term __P((void));
    110  1.6  mycroft static int exp __P((void));
    111  1.5    glass static int unary __P((void));
    112  1.5    glass static int factor __P((void));
    113  1.5    glass static int constant __P((void));
    114  1.5    glass static int num __P((void));
    115  1.6  mycroft static int geteqrel __P((void));
    116  1.5    glass static int skipws __P((void));
    117  1.5    glass static void experr __P((char *));
    118  1.5    glass 
    119  1.5    glass /*
    120  1.5    glass  * For longjmp
    121  1.5    glass  */
    122  1.5    glass #include <setjmp.h>
    123  1.5    glass static jmp_buf expjump;
    124  1.2    glass 
    125  1.5    glass /*
    126  1.5    glass  * macros:
    127  1.5    glass  *      ungetch - Put back the last character examined.
    128  1.5    glass  *      getch   - return the next character from expr string.
    129  1.5    glass  */
    130  1.5    glass #define ungetch()       nxtch--
    131  1.5    glass #define getch()         *nxtch++
    132  1.5    glass 
    133  1.5    glass int
    134  1.5    glass expr(expbuf)
    135  1.5    glass char *expbuf;
    136  1.5    glass {
    137  1.5    glass 	register int rval;
    138  1.5    glass 
    139  1.5    glass 	nxtch = expbuf;
    140  1.5    glass 	if (setjmp(expjump) != 0)
    141  1.5    glass 		return FALSE;
    142  1.5    glass 
    143  1.5    glass 	rval = query();
    144  1.5    glass 	if (skipws() == EOS)
    145  1.5    glass 		return rval;
    146  1.5    glass 
    147  1.5    glass 	printf("m4: ill-formed expression.\n");
    148  1.5    glass 	return FALSE;
    149  1.5    glass }
    150  1.5    glass 
    151  1.5    glass /*
    152  1.5    glass  * query : lor | lor '?' query ':' query
    153  1.5    glass  */
    154  1.5    glass static int
    155  1.5    glass query()
    156  1.5    glass {
    157  1.5    glass 	register int bool, true_val, false_val;
    158  1.5    glass 
    159  1.5    glass 	bool = lor();
    160  1.5    glass 	if (skipws() != '?') {
    161  1.5    glass 		ungetch();
    162  1.5    glass 		return bool;
    163  1.5    glass 	}
    164  1.5    glass 
    165  1.5    glass 	true_val = query();
    166  1.5    glass 	if (skipws() != ':')
    167  1.5    glass 		experr("bad query");
    168  1.5    glass 
    169  1.5    glass 	false_val = query();
    170  1.5    glass 	return bool ? true_val : false_val;
    171  1.5    glass }
    172  1.2    glass 
    173  1.5    glass /*
    174  1.5    glass  * lor : land { '||' land }
    175  1.5    glass  */
    176  1.5    glass static int
    177  1.5    glass lor()
    178  1.5    glass {
    179  1.5    glass 	register int c, vl, vr;
    180  1.5    glass 
    181  1.5    glass 	vl = land();
    182  1.6  mycroft 	while ((c = skipws()) == '|') {
    183  1.6  mycroft 		if (getch() != '|')
    184  1.6  mycroft 			ungetch();
    185  1.5    glass 		vr = land();
    186  1.5    glass 		vl = vl || vr;
    187  1.5    glass 	}
    188  1.5    glass 
    189  1.5    glass 	ungetch();
    190  1.5    glass 	return vl;
    191  1.5    glass }
    192  1.2    glass 
    193  1.5    glass /*
    194  1.6  mycroft  * land : not { '&&' not }
    195  1.5    glass  */
    196  1.5    glass static int
    197  1.5    glass land()
    198  1.5    glass {
    199  1.5    glass 	register int c, vl, vr;
    200  1.5    glass 
    201  1.6  mycroft 	vl = not();
    202  1.6  mycroft 	while ((c = skipws()) == '&') {
    203  1.6  mycroft 		if (getch() != '&')
    204  1.6  mycroft 			ungetch();
    205  1.6  mycroft 		vr = not();
    206  1.5    glass 		vl = vl && vr;
    207  1.5    glass 	}
    208  1.5    glass 
    209  1.5    glass 	ungetch();
    210  1.5    glass 	return vl;
    211  1.5    glass }
    212  1.2    glass 
    213  1.5    glass /*
    214  1.6  mycroft  * not : eqrel | '!' not
    215  1.5    glass  */
    216  1.5    glass static int
    217  1.6  mycroft not()
    218  1.5    glass {
    219  1.6  mycroft 	register int val, c;
    220  1.5    glass 
    221  1.6  mycroft 	if ((c = skipws()) == '!' && getch() != '=') {
    222  1.5    glass 		ungetch();
    223  1.6  mycroft 		val = not();
    224  1.6  mycroft 		return !val;
    225  1.5    glass 	}
    226  1.5    glass 
    227  1.6  mycroft 	if (c == '!')
    228  1.5    glass 		ungetch();
    229  1.5    glass 	ungetch();
    230  1.6  mycroft 	return eqrel();
    231  1.5    glass }
    232  1.2    glass 
    233  1.5    glass /*
    234  1.6  mycroft  * eqrel : shift { eqrelop shift }
    235  1.5    glass  */
    236  1.5    glass static int
    237  1.6  mycroft eqrel()
    238  1.5    glass {
    239  1.6  mycroft 	register int vl, vr, eqrel;
    240  1.5    glass 
    241  1.6  mycroft 	vl = shift();
    242  1.6  mycroft 	while ((eqrel = geteqrel()) != -1) {
    243  1.6  mycroft 		vr = shift();
    244  1.5    glass 
    245  1.6  mycroft 		switch (eqrel) {
    246  1.5    glass 
    247  1.5    glass 		case EQL:
    248  1.5    glass 			vl = (vl == vr);
    249  1.5    glass 			break;
    250  1.5    glass 		case NEQ:
    251  1.5    glass 			vl = (vl != vr);
    252  1.5    glass 			break;
    253  1.5    glass 
    254  1.5    glass 		case LEQ:
    255  1.5    glass 			vl = (vl <= vr);
    256  1.5    glass 			break;
    257  1.5    glass 		case LSS:
    258  1.5    glass 			vl = (vl < vr);
    259  1.5    glass 			break;
    260  1.5    glass 		case GTR:
    261  1.5    glass 			vl = (vl > vr);
    262  1.5    glass 			break;
    263  1.5    glass 		case GEQ:
    264  1.5    glass 			vl = (vl >= vr);
    265  1.5    glass 			break;
    266  1.5    glass 		}
    267  1.2    glass 	}
    268  1.2    glass 	return vl;
    269  1.5    glass }
    270  1.2    glass 
    271  1.5    glass /*
    272  1.5    glass  * shift : primary { shop primary }
    273  1.5    glass  */
    274  1.5    glass static int
    275  1.5    glass shift()
    276  1.5    glass {
    277  1.5    glass 	register int vl, vr, c;
    278  1.5    glass 
    279  1.5    glass 	vl = primary();
    280  1.6  mycroft 	while (((c = skipws()) == '<' || c == '>') && getch() == c) {
    281  1.5    glass 		vr = primary();
    282  1.5    glass 
    283  1.5    glass 		if (c == '<')
    284  1.5    glass 			vl <<= vr;
    285  1.5    glass 		else
    286  1.5    glass 			vl >>= vr;
    287  1.5    glass 	}
    288  1.5    glass 
    289  1.5    glass 	if (c == '<' || c == '>')
    290  1.5    glass 		ungetch();
    291  1.5    glass 	ungetch();
    292  1.5    glass 	return vl;
    293  1.5    glass }
    294  1.2    glass 
    295  1.5    glass /*
    296  1.5    glass  * primary : term { addop term }
    297  1.5    glass  */
    298  1.5    glass static int
    299  1.5    glass primary()
    300  1.5    glass {
    301  1.5    glass 	register int c, vl, vr;
    302  1.5    glass 
    303  1.5    glass 	vl = term();
    304  1.5    glass 	while ((c = skipws()) == '+' || c == '-') {
    305  1.5    glass 		vr = term();
    306  1.6  mycroft 
    307  1.5    glass 		if (c == '+')
    308  1.5    glass 			vl += vr;
    309  1.5    glass 		else
    310  1.5    glass 			vl -= vr;
    311  1.2    glass 	}
    312  1.5    glass 
    313  1.5    glass 	ungetch();
    314  1.2    glass 	return vl;
    315  1.5    glass }
    316  1.2    glass 
    317  1.5    glass /*
    318  1.6  mycroft  * <term> := <exp> { <mulop> <exp> }
    319  1.5    glass  */
    320  1.5    glass static int
    321  1.5    glass term()
    322  1.5    glass {
    323  1.5    glass 	register int c, vl, vr;
    324  1.5    glass 
    325  1.6  mycroft 	vl = exp();
    326  1.5    glass 	while ((c = skipws()) == '*' || c == '/' || c == '%') {
    327  1.6  mycroft 		vr = exp();
    328  1.2    glass 
    329  1.5    glass 		switch (c) {
    330  1.5    glass 		case '*':
    331  1.5    glass 			vl *= vr;
    332  1.5    glass 			break;
    333  1.5    glass 		case '/':
    334  1.5    glass 			vl /= vr;
    335  1.5    glass 			break;
    336  1.5    glass 		case '%':
    337  1.5    glass 			vl %= vr;
    338  1.5    glass 			break;
    339  1.5    glass 		}
    340  1.2    glass 	}
    341  1.5    glass 	ungetch();
    342  1.2    glass 	return vl;
    343  1.5    glass }
    344  1.2    glass 
    345  1.5    glass /*
    346  1.6  mycroft  * <term> := <unary> { <expop> <unary> }
    347  1.6  mycroft  */
    348  1.6  mycroft static int
    349  1.6  mycroft exp()
    350  1.6  mycroft {
    351  1.6  mycroft 	register c, vl, vr, n;
    352  1.6  mycroft 
    353  1.6  mycroft 	vl = unary();
    354  1.6  mycroft 	switch (c = skipws()) {
    355  1.6  mycroft 
    356  1.6  mycroft 	case '*':
    357  1.6  mycroft 		if (getch() != '*') {
    358  1.6  mycroft 			ungetch();
    359  1.6  mycroft 			break;
    360  1.6  mycroft 		}
    361  1.6  mycroft 
    362  1.6  mycroft 	case '^':
    363  1.6  mycroft 		vr = exp();
    364  1.6  mycroft 		n = 1;
    365  1.6  mycroft 		while (vr-- > 0)
    366  1.6  mycroft 			n *= vl;
    367  1.6  mycroft 		return n;
    368  1.6  mycroft 	}
    369  1.6  mycroft 
    370  1.6  mycroft 	ungetch();
    371  1.6  mycroft 	return vl;
    372  1.6  mycroft }
    373  1.6  mycroft 
    374  1.6  mycroft /*
    375  1.5    glass  * unary : factor | unop unary
    376  1.5    glass  */
    377  1.5    glass static int
    378  1.5    glass unary()
    379  1.5    glass {
    380  1.5    glass 	register int val, c;
    381  1.5    glass 
    382  1.6  mycroft 	if ((c = skipws()) == '+' || c == '-' || c == '~') {
    383  1.5    glass 		val = unary();
    384  1.5    glass 
    385  1.5    glass 		switch (c) {
    386  1.6  mycroft 		case '+':
    387  1.6  mycroft 			return val;
    388  1.6  mycroft 		case '-':
    389  1.6  mycroft 			return -val;
    390  1.5    glass 		case '~':
    391  1.5    glass 			return ~val;
    392  1.5    glass 		}
    393  1.5    glass 	}
    394  1.2    glass 
    395  1.5    glass 	ungetch();
    396  1.5    glass 	return factor();
    397  1.5    glass }
    398  1.5    glass 
    399  1.5    glass /*
    400  1.5    glass  * factor : constant | '(' query ')'
    401  1.5    glass  */
    402  1.5    glass static int
    403  1.5    glass factor()
    404  1.5    glass {
    405  1.5    glass 	register int val;
    406  1.5    glass 
    407  1.5    glass 	if (skipws() == '(') {
    408  1.5    glass 		val = query();
    409  1.5    glass 		if (skipws() != ')')
    410  1.5    glass 			experr("bad factor");
    411  1.5    glass 		return val;
    412  1.5    glass 	}
    413  1.5    glass 
    414  1.5    glass 	ungetch();
    415  1.5    glass 	return constant();
    416  1.5    glass }
    417  1.5    glass 
    418  1.5    glass /*
    419  1.5    glass  * constant: num | 'char'
    420  1.5    glass  * Note: constant() handles multi-byte constants
    421  1.5    glass  */
    422  1.5    glass static int
    423  1.5    glass constant()
    424  1.5    glass {
    425  1.5    glass 	register int i;
    426  1.5    glass 	register int value;
    427  1.5    glass 	register char c;
    428  1.5    glass 	int v[sizeof(int)];
    429  1.5    glass 
    430  1.5    glass 	if (skipws() != '\'') {
    431  1.5    glass 		ungetch();
    432  1.5    glass 		return num();
    433  1.5    glass 	}
    434  1.5    glass 	for (i = 0; i < sizeof(int); i++) {
    435  1.5    glass 		if ((c = getch()) == '\'') {
    436  1.5    glass 			ungetch();
    437  1.5    glass 			break;
    438  1.5    glass 		}
    439  1.5    glass 		if (c == '\\') {
    440  1.5    glass 			switch (c = getch()) {
    441  1.5    glass 			case '0':
    442  1.5    glass 			case '1':
    443  1.5    glass 			case '2':
    444  1.5    glass 			case '3':
    445  1.5    glass 			case '4':
    446  1.5    glass 			case '5':
    447  1.5    glass 			case '6':
    448  1.5    glass 			case '7':
    449  1.5    glass 				ungetch();
    450  1.5    glass 				c = num();
    451  1.5    glass 				break;
    452  1.5    glass 			case 'n':
    453  1.5    glass 				c = 012;
    454  1.5    glass 				break;
    455  1.5    glass 			case 'r':
    456  1.5    glass 				c = 015;
    457  1.5    glass 				break;
    458  1.5    glass 			case 't':
    459  1.5    glass 				c = 011;
    460  1.5    glass 				break;
    461  1.5    glass 			case 'b':
    462  1.5    glass 				c = 010;
    463  1.5    glass 				break;
    464  1.5    glass 			case 'f':
    465  1.5    glass 				c = 014;
    466  1.5    glass 				break;
    467  1.5    glass 			}
    468  1.5    glass 		}
    469  1.5    glass 		v[i] = c;
    470  1.5    glass 	}
    471  1.5    glass 	if (i == 0 || getch() != '\'')
    472  1.5    glass 		experr("illegal character constant");
    473  1.5    glass 	for (value = 0; --i >= 0;) {
    474  1.5    glass 		value <<= 8;
    475  1.5    glass 		value += v[i];
    476  1.5    glass 	}
    477  1.5    glass 	return value;
    478  1.5    glass }
    479  1.2    glass 
    480  1.5    glass /*
    481  1.5    glass  * num : digit | num digit
    482  1.5    glass  */
    483  1.5    glass static int
    484  1.5    glass num()
    485  1.5    glass {
    486  1.5    glass 	register int rval, c, base;
    487  1.5    glass 	int ndig;
    488  1.5    glass 
    489  1.5    glass 	base = ((c = skipws()) == '0') ? OCTAL : DECIMAL;
    490  1.5    glass 	rval = 0;
    491  1.5    glass 	ndig = 0;
    492  1.5    glass 	while (c >= '0' && c <= (base == OCTAL ? '7' : '9')) {
    493  1.5    glass 		rval *= base;
    494  1.5    glass 		rval += (c - '0');
    495  1.5    glass 		c = getch();
    496  1.5    glass 		ndig++;
    497  1.5    glass 	}
    498  1.5    glass 	ungetch();
    499  1.5    glass 
    500  1.5    glass 	if (ndig == 0)
    501  1.5    glass 		experr("bad constant");
    502  1.5    glass 
    503  1.5    glass 	return rval;
    504  1.2    glass 
    505  1.5    glass }
    506  1.1      cgd 
    507  1.5    glass /*
    508  1.6  mycroft  * eqrel : '=' | '==' | '!=' | '<' | '>' | '<=' | '>='
    509  1.5    glass  */
    510  1.5    glass static int
    511  1.6  mycroft geteqrel()
    512  1.5    glass {
    513  1.5    glass 	register int c1, c2;
    514  1.5    glass 
    515  1.5    glass 	c1 = skipws();
    516  1.5    glass 	c2 = getch();
    517  1.5    glass 
    518  1.5    glass 	switch (c1) {
    519  1.5    glass 
    520  1.5    glass 	case '=':
    521  1.5    glass 		if (c2 != '=')
    522  1.5    glass 			ungetch();
    523  1.5    glass 		return EQL;
    524  1.5    glass 
    525  1.5    glass 	case '!':
    526  1.5    glass 		if (c2 == '=')
    527  1.5    glass 			return NEQ;
    528  1.5    glass 		ungetch();
    529  1.5    glass 		ungetch();
    530  1.5    glass 		return -1;
    531  1.5    glass 
    532  1.5    glass 	case '<':
    533  1.5    glass 		if (c2 == '=')
    534  1.5    glass 			return LEQ;
    535  1.5    glass 		ungetch();
    536  1.5    glass 		return LSS;
    537  1.5    glass 
    538  1.5    glass 	case '>':
    539  1.5    glass 		if (c2 == '=')
    540  1.5    glass 			return GEQ;
    541  1.5    glass 		ungetch();
    542  1.5    glass 		return GTR;
    543  1.5    glass 
    544  1.5    glass 	default:
    545  1.5    glass 		ungetch();
    546  1.5    glass 		ungetch();
    547  1.5    glass 		return -1;
    548  1.5    glass 	}
    549  1.5    glass }
    550  1.5    glass 
    551  1.5    glass /*
    552  1.5    glass  * Skip over any white space and return terminating char.
    553  1.5    glass  */
    554  1.5    glass static int
    555  1.5    glass skipws()
    556  1.5    glass {
    557  1.5    glass 	register char c;
    558  1.5    glass 
    559  1.5    glass 	while ((c = getch()) <= ' ' && c > EOS)
    560  1.5    glass 		;
    561  1.5    glass 	return c;
    562  1.5    glass }
    563  1.5    glass 
    564  1.5    glass /*
    565  1.5    glass  * resets environment to eval(), prints an error
    566  1.5    glass  * and forces eval to return FALSE.
    567  1.5    glass  */
    568  1.5    glass static void
    569  1.5    glass experr(msg)
    570  1.5    glass char *msg;
    571  1.5    glass {
    572  1.5    glass 	printf("m4: %s in expr.\n", msg);
    573  1.5    glass 	longjmp(expjump, -1);
    574  1.5    glass }
    575