UNIX — универсальная среда программирования

Керниган Брайан Уилсон

}

double integer(x)

 double x;

{

 return (double)(long)x;

}

double errcheck(d, s) /* check result of library call */

 double d;

 char *s;

{

 if (errno == EDOM) {

errno = 0;

execerror(s, "argument out of domain");

 } else if (errno == ERANGE) {

errno = 0;

execerror(s, "result out of range");

 }

 return d;

}

3.6.9

symbol.c

#include "hoc.h"

#include "y.tab.h"

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;

}

3.7

hoc6

3.7.1

ack

func ack {

 n = n+1

 if ($1 == 0) return ($2+1)

 if ($2 == 0) return (ack($1 - 1, 1))

 return (ack($1 - 1, ack($1, $2 - 1)))

}

n=0

ack(3,3)

print n, "calls\n"

3.7.2

ack1

func ack {

 n = n+1

 if ($1 == 0) return ($2+1)

 if ($2 == 0) return (ack($1 - 1, 1))

 return (ack($1 - 1, ack($1, $2 - 1)))

}

n=0

while (read(x)) {

 read(y)

 print ack(x,y), "\n"

}

print n,"\n"

3.7.3

code.c

#include "hoc.h"

#include "y.tab.h"

#include <stdio.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 */

Inst *progbase = prog; /* start of current subprogram */

int returning; /* 1 if return stmt seen */

typedef struct Frame { /* proc/func call stack frame */

 Symbol *sp; /* symbol table entry */

 Inst *retpc; /* where to resume after return */

 Datum *argn; /* n-th argument on stack */

 int nargs; /* number of arguments */

} Frame;

#define NFRAME 100

Frame frame[NFRAME];

Frame *fp; /* frame pointer */

initcode {

 progp = progbase;

 stackp = stack;

 fp = frame;

 returning = 0;

}

push(d)