UNIX — универсальная среда программирования - Керниган Брайан Уилсон
;
cond: '(' expr ')' { code(STOP); $$ = $2; }
;
while: WHILE { $$ = code3(whilecode, STOP, STOP); }
;
if: IF { $$=code(ifcode); code3(STOP, STOP, STOP); }
;
end: /* nothing */ { code(STOP); $$ = progp; }
;
stmtlist: /* nothing */ { $$ = progp; }
| stmtlist 'n'
| stmtlist stmt
;
expr: NUMBER { $$ = code2(constpush, (Inst)$1); }
| VAR { $$ = code3(varpush, (Inst)$1, eval); }
| asgn
| BLTIN '(' expr ')'
{ $$ = $3; code2(bltin,(Inst)$1->u.ptr); }
| '(' expr ')' { $$ = $2; }
| expr '+' expr { code(add); }
| expr '-' expr { code(sub); }
| expr '*' expr { code(mul); }
| expr '/' expr { code(div); }
| expr '^' expr { code (power); }
| '-' expr %prec UNARYMINUS { $$ = $2; code(negate); }
| expr GT expr { code(gt); }
| expr GE expr { code(ge); }
| expr LT expr { code(lt); }
| expr LE expr { code(le); }
| expr EQ expr { code(eq); }
| expr NE expr { code(ne); }
| expr AND expr { code(and); }
| expr OR expr { code(or); }
| NOT expr { $$ = $2; code(not); }
;
%%
/* end of grammar */
#include <stdio.h>
#include <ctype.h>
char *progname;
int lineno = 1;
#include <signal.h>
#include <setjmp.h>
jmp_buf begin;
int defining;
int c; /* global for use by warning() */
yylex() /* hoc5 */
{
while ((c=getchar()) == ' ' || c == 't')
;
if (c == EOF)
return 0;
if (c == '.' || isdigit(c)) { /* number */
double d;
ungetc(c, stdin);
scanf("%lf", &d);
yylval.sym = install("", NUMBER, d);
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 = ' ';
if ((s=lookup(sbuf)) == 0)
s = install(sbuf, UNDEF, 0.0);
yylval.sym = s;
return s->type == UNDEF ? VAR : s->type;
}
switch (c) {
case '>': return follow('=', GE, GT);
case '<': return follow('=', LE, LT);
case '=': return follow('=', EQ, '=');
case '!': return follow('=', NE, NOT);
case '|': return follow('|', OR, '|');
case '&': return follow('&', AND, '&');
case 'n': lineno++; return 'n';
default: return c;
}
}
follow(expect, ifyes, ifno) /* look ahead for >=, etc. */
{
int c = getchar();
if (c == expect)
return ifyes;
ungetc(c, stdin);
return ifno;
}
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);
}
main(argc, argv)
char *argv[];
{
