UNIX — универсальная среда программирования - Керниган Брайан Уилсон

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Автор Керниган Брайан Уилсон

static Symbol *symlist =0; /* symbol table: linked list */

Symbol *lookup(s) /* find s in symbol table */

char *s;

{

Symbol *sp;

for (sp = symlist; sp != (Symbol*)0; sp = sp->next)

if (strcmp(sp->name, s) == 0)

return sp;

return 0; /* 0 ==> not found */

}

Symbol *install(s, t, d) /* install s in symbol table */

char *s;

int t;

double d;

{

Symbol *sp;

char *emalloc();

sp = (Symbol*)emalloc(sizeof(Symbol));

sp->name = emalloc(strlen(s)+1); /* +1 for '\0' */

strcpy(sp->name, s);

sp->type = t;

sp->u.val = d;

sp->next = symlist; /* put at front of list */

symlist = sp;

return sp;

}

char *emalloc(n) /* check return from malloc */

unsigned n;

{

char *p, *malloc();

p = malloc(n);

if (p == 0)

execerror("out of memory", (char*)0);

return p;

}

3.5

hoc4

3.5.1

code.c

#include "hoc.h"

#include "y.tab.h"

#define NSTACK 256

static Datum stack[NSTACK]; /* the stack */

static Datum *stackp; /* next free spot on stack */

#define NPROG 2000

Inst prog[NPROG]; /* the machine */

Inst *progp; /* next free spot for code generation */

Inst *pc; /* program counter during execution */

initcode() /* initialize for code generation */

{

stackp = stack;

progp = prog;

}

push(d) /* push d onto stack */

Datum d;

{

if (stackp >= &stack[NSTACK])

execerror("stack overflow", (char*)0);

*stackp++ = d;

}

Datum pop() /* pop and return top elem from stack */

{

if (stackp <= stack)

execerror("stack underflow", (char*)0);

return *--stackp;

}

constpush() /* push constant onto stack */

{

Datum d;

d.val = ((Symbol*)*pc++)->u.val;

push(d);

}

varpush() /* push variable onto stack */

{

Datum d;

d.sym = (Symbol*)(*pc++);

push(d);

}

bltin() /* evaluate built-in on top of stack */

{

Datum d;

d = pop();

d.val = (*(double(*)())(*pc++))(d.val);

push(d);

}

eval() /* evaluate variable on stack */

{

Datum d;

d = pop() ;

if (d.sym->type == UNDEF)

execerror("undefined variable", d.sym->name);

d.val = d.sym->u.val;

push(d);

}

add() /* add top two elems on stack */

{

Datum d1, d2;

d2 = pop();

d1 = pop();

d1.val += d2.val;

push(d1);

}

sub() /* subtract top of stack from next */

{

Datum d1, d2;

d2 = pop();

d1 = pop();