Книга: UNIX — универсальная среда программирования
3.5.3 hoc.y
3.5.3 hoc.y
%{
#include "hoc.h"
#define code2(c1,c2) code(c1); code(c2)
#define code3(c1,c2,c3) code(c1); code(c2); code(c3)
%}
%union {
Symbol *sym; /* symbol table pointer */
Inst *inst; /* machine instruction */
}
%token <sym> NUMBER VAR BLTIN UNDEF
%right '='
%left '+' '-'
%left '*' '/'
%left UNARYMINUS
%right '^' /* exponentiation */
%%
list: /* nothing */
| list 'n'
| list asgn 'n' { code2(pop, STOP); return 1; }
| list expr 'n' { code2(print, STOP); return 1; }
| list error 'n' { yyerrok; }
;
asgn: VAR '=' expr { code3(varpush,(Inst)$1.assign); }
;
expr: NUMBER { code2(constpush, (Inst)$1); }
| VAR { code3(varpush, (Inst)$1, eval); }
| asgn
| BLTIN '(' expr ')' { code2(bltin, (Inst)$1->u.ptr); }
| '(' expr ')'
| expr '+' expr { code(add); }
| expr '-' expr { code(sub); }
| expr '*' expr { code(mul); }
| expr '/' expr { code(div); }
| expr '^' expr { code(power); }
| '-' expr %prec UNARYMINUS { code(negate); }
;
%%
/* 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) /* hoc4 */
char *argv[];
{
int fpecatch();
progname = argv[0];
init();
setjmp(begin);
signal(SIGFPE, fpecatch);
for (initcode(); yyparse(); initcode())
execute(prog);
return 0;
}
static int c; /* global for use by warning() */
yylex() /* hoc4 */
{
while ((c=getchar()) == ' ' || с == '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;
}
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 %dn", lineno);
while (c != 'n' && с != EOF)
с = getchar(); /* flush rest of input line */
}