Книга: UNIX — универсальная среда программирования

3.6.5 hoc.y

3.6.5 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 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() */
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[];
{
 int fpecatch();
 progname = argv[0];
 init();
 setjmp(begin);
 signal(SIGFPE, fpecatch);
 for (initcode(); yyparse(); initcode())
  execute(prog);
 return 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)
  c = getchar(); /* flush rest of input line */
 fseek(stdin, 0L, 2); /* flush rest of file */
 longjmp(begin, 0);
}

Оглавление книги