UNIX — универсальная среда программирования

  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;
 }

3.6 hoc5

3.6.1 code.c

 #include "hoc.h"
 #include "y.tab.h"

 #define NSTACK 256
 static Datum stack[NSTACK];
 static Datum *stackp;

 #define NPROG 2000
 Inst prog[NPROG];
 static Inst *pc;
 Inst *progp;

 initcode {
  progp = prog;
  stackp = stack;
 }

 push(d)
  Datum d;
 {
  if (stackp >= &stack[NSTACK])
  execerror("stack too deep", (char*)0);
  *stackp++ = d;
 }

 Datum pop {
  if (stackp == stack)
  execerror("stack underflow", (char*)0);
  return *--stackp;
 }

 constpush {
  Datum d;
  d.val = ((Symbol*)*pc++)->u.val;
  push(d);
 }

 varpush {
  Datum d;
  d.sym = (Symbol*)(*pc++);
  push(d);
 }

 whilecode {
  Datum d;
  Inst *savepc = pc; /* loop body */
  execute(savepc+2); /* condition */
  d = pop;
  while (d.val) {
  execute (*((Inst**)(savepc))); /* body */
  execute(savepc+2);
  d = pop;
  }
  pc = *((Inst**)(savepc+1)); /* next statement */
 }

 ifcode {
  Datum d;
  Inst *savepc = pc; /* then part */
  execute(savepc+3); /* condition */
  d = pop;
  if (d.val)
  execute(*((Inst**)(savepc)));
  else if (*((Inst**)(savepc+1))) /* else part? */
  execute(*((Inst**)(savepc+1)));
  pc = *((Inst**)(savepc+2)); /* next stmt */
 }

 bltin {
  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 != VAR && d.sym->type != UNDEF)
  execerror("attempt to evaluate non-variable", d.sym->name);
  if (d.sym->type == UNDEF)
  execerror("undefined variable", d.sym->name);
  d.val = d.sym->u.val;
  push(d);
 }

 add {
  Datum d1, d2;
  d2 = pop;
  d1 = pop;
  d1.val += d2.val;
  push(d1);
 }

 sub {
  Datum d1, d2;
  d2 = pop;
  d1 = pop;
  d1.val -= d2.val;
  push(d1);
 }

 mul {
  Datum d1, d2;
  d2 = pop;
  d1 = pop;
  d1.val *= d2.val;
  push(d1);
 }

 div {
  Datum d1, d2;
  d2 = pop;
  if (d2.val == 0.0)
  execerror("division by zero", (char*)0);
  d1 = pop;
  d1.val /= d2.val;
  push(d1);
 }

 negate {
  Datum d;
  d = pop;
  d.val = -d.val;
  push(d);
 }

 gt {
  Datum d1, d2;