Category : OS/2 Files
Archive   : KSH48.ZIP
Filename : EXPR.C

 
Output of file : EXPR.C contained in archive : KSH48.ZIP
/*
* Korn expression evaluation
*/

#ifndef lint
static char *RCSid = "$Id: expr.c,v 1.2 1992/04/25 08:33:28 sjg Exp $";
#endif

#include "stdh.h"
#include
#include
#include "sh.h"

#define ef else if /* fashion statement */

#define VAR 0x01
#define LIT 0x02
#define LEQ 0x03
#define LNE 0x04
#define LLE 0x05
#define LGE 0x06

static char *expression; /* expression being evaluated */
static char *tokp; /* lexical position */
static int tok; /* token from token() */
static struct tbl *val; /* value from token() */

static struct tbl *asn ARGS((void));
static struct tbl *e6 ARGS((void));
static struct tbl *e5 ARGS((void));
static struct tbl *e3 ARGS((void));
static struct tbl *e2 ARGS((void));
static struct tbl *e0 ARGS((void));
static void token ARGS((void));
static struct tbl *tempvar ARGS((void));
static struct tbl *intvar ARGS((struct tbl *vp));

/*
* parse and evalute expression
*/
void
evalerr(err)
char *err;
{
errorf("%s: %s\n", expression, err);
}

long
evaluate(expr)
const char *expr;
{
struct tbl *v;

expression = tokp = (char *) expr;
token();
v = intvar(asn());
if (!(tok == 0))
evalerr("bad expression");
return v->val.i;
}

static struct tbl *
asn()
{
register struct tbl *vl, *vr;

vr = vl = e6();
if ((tok == '=')) {
Area * olastarea = lastarea;
token();
if ((vl->flag&RDONLY)) /* assign to rvalue */
evalerr("bad assignment");
vr = intvar(asn());
lastarea = olastarea;
setint(vl, vr->val.i);
if ((vl->flag&INTEGER) && vl->type == 0) /* default base? */
vl->type = vr->type;
}
return vr;
}

static struct tbl *
e6()
{
register struct tbl *vl, *vr;

vl = e5();
while ((tok == LEQ) || (tok == LNE)) {
int op = tok;
token();
vl = intvar(vl);
vr = intvar(e5());
vl->val.i = vl->val.i == vr->val.i;
if (op == LNE)
vl->val.i = ! vl->val.i;
}
return vl;
}

static struct tbl *
e5()
{
register struct tbl *vl, *vr;

vl = e3();
while ((tok == LLE) || (tok == '<') || (tok == '>') || (tok == LGE)) {
int op = tok;
token();
vl = intvar(vl);
vr = intvar(e3());
if (op == LLE)
vl->val.i = vl->val.i <= vr->val.i;
ef (op == '<')
vl->val.i = vl->val.i < vr->val.i;
ef (op == LGE)
vl->val.i = vl->val.i >= vr->val.i;
ef (op == '>')
vl->val.i = vl->val.i > vr->val.i;
}
return vl;
}

static struct tbl *
e3()
{
register struct tbl *vl, *vr;

vl = e2();
while ((tok == '+') || (tok == '-')) {
int op = tok;
token();
vl = intvar(vl);
vr = intvar(e2());
if (op == '+')
vl->val.i += vr->val.i;
ef (op == '-')
vl->val.i -= vr->val.i;
}
return vl;
}

static struct tbl *
e2()
{
register struct tbl *vl, *vr;

vl = e0();
while ((tok == '*') || (tok == '/') || (tok == '%')) {
int op = tok;
token();
vl = intvar(vl);
vr = intvar(e0());
if (op != '*' && vr->val.i == 0)
evalerr("zero divisor");
if (op == '*')
vl->val.i *= vr->val.i;
ef (op == '/')
vl->val.i /= vr->val.i;
ef (op == '%')
vl->val.i %= vr->val.i;
}
return vl;
}

static struct tbl *
e0()
{
register struct tbl *v;

if ((tok == '!') || (tok == '-')) {
int op = tok;
token();
v = intvar(e0());
if (op == '!')
v->val.i = !v->val.i;
ef (op == '-')
v->val.i = -v->val.i;
} else
if ((tok == '(')) {
token();
v = asn();
if (!(tok == ')'))
evalerr("missing )");
token();
} else
if ((tok == VAR) || (tok == LIT)) {
v = val;
token();
} else
evalerr("bad expression");
return v;
}

static void
token()
{
register char *cp = (char *) tokp;
register int c, c2;

/* skip white space */
do c = *cp++; while (c != '\0' && (c == ' ' || c == '\t'));
tokp = cp-1;

if (letter(c)) {
for (; letnum(c); c = *cp++)
;
c = *--cp;
*cp = 0;
val = global(tokp);
*cp = c;
tok = VAR;
} else
if (digit(c)) {
for (; letnum(c) || c == '#'; c = *cp++)
;
c = *--cp;
*cp = 0;
val = tempvar();
setstr(val, tokp);
val->flag |= RDONLY;
*cp = c;
tok = LIT;
} else {
c2 = *cp++;
if (c == '=' && c2 == '=')
c = LEQ;
ef (c == '!' && c2 == '=')
c = LNE;
ef (c == '<' && c2 == '=')
c = LLE;
ef (c == '>' && c2 == '=')
c = LGE;
else
cp--;
tok = c;
}
tokp = cp;
}

static struct tbl *
tempvar()
{
register struct tbl *vp;

vp = (struct tbl*) alloc(sizeof(struct tbl), ATEMP);
lastarea = ATEMP;
vp->flag = ISSET|INTEGER;
vp->type = 0;
vp->name[0] = '\0';
return vp;
}

/* cast (string) variable to temporary integer variable */
static struct tbl *
intvar(vp)
register struct tbl *vp;
{
register struct tbl *vq;

vq = tempvar();
vq->type = 10;
if (strint(vq, vp) == NULL) {
if ((vp->flag&ISSET) && vp->val.s && *(vp->val.s)) {
evalerr("bad number");
} else {
vq->flag |= (ISSET|INTEGER);
vq->type = 10;
vq->val.i = 0;
}
}
return vq;
}



  3 Responses to “Category : OS/2 Files
Archive   : KSH48.ZIP
Filename : EXPR.C

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