Шрифт:
| expr '+' expr { $$ = $1 + $3; }
| expr '-' expr { $$ = $1 - $3; }
| expr '*' expr { $$ = $1 * $3; }
| expr '/' expr {
if ($3 == 0.0)
execerror("division by zero", "");
$$ = $1 / $3;
}
| expr '^' expr { $$ = Pow($1, $3); }
| '(' expr ')' { $$ = $2; }
| '-' expr %prec UNARYMINUS { $$ = -$2; }
;
%%
/* end of grammar */
#include <stdio.h>
#include <ctype.h>
char *progname;
int lineno = 1;
#include <signal.h>
#include <setjmp.h>
jmp_buf begin;
main(argc, argv) /* hoc3 */
char *argv[];
{
int fpecatch;
progname = argv[0];
init;
setjmp(begin);
signal(SIGFPE, fpecatch);
yyparse;
}
yylex /* hoc3 */
{
int c;
while ((c=getchar) == ' ' || c == '\t')
;
if (c == EOF)
return 0;
if (c == '.' || isdigit(c)) {
/* number */
ungetc(c, stdin);
scanf("%lf", &yylval.val);
return NUMBER;
}
if (isalpha(c)) {
Symbol *s;
char sbuf[100], *p = sbuf;
do {
*p++ = c;
} while ((c=getchar) != EOF && isalnum(c));
ungetc(c, stdin);
*p = '\0';
if ((s=lookup(sbuf)) == 0)
s = install(sbuf, UNDEF, 0.0);
yylval.sym = s;
return s->type == UNDEF ? VAR : s->type;
}
if (c == '\n')
lineno++;
return c;
}
yyerror(s)
char *s;
{
warning(s, (char *)0);
}
execerror(s, t) /* recover from run-time error */
char *s, *t;
{
warning(s, t);
longjmp(begin, 0);
}
fpecatch /* catch floating point exceptions */
execerror("floating point exception", (char*)0);
}
warning(s, t)
char *s, *t;
{
fprintf(stderr, "%s: %s", progname, s);
if (t && *t)
fprintf (stderr, " %s", t);
fprintf(stderr, " near line %d\n", lineno);
}
3.3.4
init.c
#include "hoc.h"
#include "y.tab.h"
#include <math.h>
extern double Log, Log10, Exp, Sqrt, integer;
static struct { /* Constants */
char *name;
double eval;
} consts[] = {
"PI", 3.14159265358979323846,
"E", 2.71828182845904523536,
"GAMMA", 0.57721566490153286060, /* Euler */
"DEG", 57.29577951308232087680, /* deg/radian */