UNIX — универсальная среда программирования

Керниган Брайан Уилсон

 Inst *p;

{

 for (pc = p; *pc != STOP; )

(*(*pc++));

}

3.5.2

hoc.h

typedef struct Symbol { /* symbol table entry */

 char *name;

 short type; /* VAR, BLTIN, UNDEF */

 union {

double val; /* if VAR */

double (*ptr); /* if BLTIN */

 } u;

 struct Symbol *next; /* to link to another */

} Symbol;

Symbol *install, *lookup;

typedef union Datum { /* interpreter stack type */

 double val;

 Symbol *sym;

} Datum;

extern Datum pop;

typedef int (*Inst); /* machine instruction */

#define STOP (Inst)0

extern Inst prog[];

extern eval, add, sub, mul, div, negate, power;

extern assign, bltin, varpush, constpush, print;

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 = '\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;