Шрифт:
Inst *inst; /* machine instruction */
}
%token <sym> NUMBER PRINT VAR BLTIN UNDEF WHILE IF ELSE
%type <inst> stmt asgn expr stmtlist cond while if end
%right '='
%left OR
%left AND
%left GT GE LT LE EQ NE
%left '+' '-'
%left '*' '/'
%left UNARYMINUS NOT
%right
%%
list: /* nothing */
| list '\n'
| list asgn '\n' { code2(pop, STOP); return 1; }
| list stmt '\n' { code(STOP); return 1; }
| list expr '\n' { code2(print, STOP); return 1; }
| list error '\n' { yyerrok; }
;
asgn: VAR '=' expr { $$=$3; code3(varpush,(Inst)$1.assign); }
;
stmt: expr { code(pop); }
| PRINT expr { code(prexpr); $$ = $2; }
| while cond stmt end {
($1)[1] = (Inst)$3; /* body of loop */
($1)[2] = (Inst)$4;
} /* end, if cond fails */
| if cond stmt end { /* else-less if */
($1)[1] = (Inst)$3; /* thenpart */
($1)[2] = (Inst)$4;
} /* end, if cond fails */
| if cond stmt end ELSE stmt end { /* if with else */
($1)[1] = (Inst)$3; /* thenpart */
($1)[2] = (Inst)$6; /* elsepart */
($1)[3] = (Inst)$7;
} /* end, if cond fails */
| '{' stmtlist '}' { $$ = $2; }
;
cond: '(' expr ')' { code(STOP); $$ = $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 */