src/common/caldefn.c

/* Copyright (c) 1986 Regents of the University of California */

#ifndef lint
static char SCCSid[] = "$SunId$ LBL";
#endif

/*
 *  Store variable definitions.
 *
 *  7/1/85  Greg Ward
 *
 *  11/11/85  Added conditional compiles (OUTCHAN) for control output.
 *
 *  4/2/86  Added conditional compiles for function definitions (FUNCTION).
 *
 *  1/15/88  Added clock for caching of variable values.
 *
 *  11/16/88  Added VARDEF structure for hard linking.
 *
 *  5/31/90  Added conditional compile (REDEFW) for redefinition warning.
 */

#include  <stdio.h>

#include  <ctype.h>

#include  "calcomp.h"

#ifndef  NHASH
#define  NHASH          521             /* hash size (a prime!) */
#endif

#define  newnode()      (EPNODE *)ecalloc(1, sizeof(EPNODE))

extern char  *ecalloc(), *savestr();

extern double  dvalue();

long  eclock = -1;                      /* value storage timer */

static VARDEF  *hashtbl[NHASH];         /* definition list */
static int  htndx;                      /* index for */         
static VARDEF  *htpos;                  /* ...dfirst() and */
#ifdef  OUTCHAN
static EPNODE  *ochpos;                 /* ...dnext */
static EPNODE  *outchan;
#endif

#ifdef  FUNCTION
EPNODE  *curfunc;
#define  dname(ep)      ((ep)->v.kid->type == SYM ? \
                        (ep)->v.kid->v.name : \
                        (ep)->v.kid->v.kid->v.name)
#else
#define  dname(ep)      ((ep)->v.kid->v.name)
#endif


fcompile(fname)                 /* get definitions from a file */
char  *fname;
{
    FILE  *fp;

    if (fname == NULL)
        fp = stdin;
    else if ((fp = fopen(fname, "r")) == NULL) {
        eputs(fname);
        eputs(": cannot open\n");
        quit(1);
    }
    initfile(fname, fp);
    while (nextc != EOF)
        loaddefn();
    if (fname != NULL)
        fclose(fp);
}


scompile(file, str)             /* get definitions from a string */
char  *file;
char  *str;
{
    initstr(file, str);
    while (nextc != EOF)
        loaddefn();
}


double
varvalue(vname)                 /* return a variable's value */
char  *vname;
{
    return(dvalue(vname, dlookup(vname)));
}


double
evariable(ep)                   /* evaluate a variable */
EPNODE  *ep;
{
    register VARDEF  *dp = ep->v.ln;

    return(dvalue(dp->name, dp->def));
}


varset(vname, val)              /* set a variable's value */
char  *vname;
double  val;
{
    register EPNODE  *ep1, *ep2;
                                        /* check for quick set */
    if ((ep1 = dlookup(vname)) != NULL && ep1->v.kid->type == SYM) {
        ep2 = ep1->v.kid->sibling;
        if (ep2->type == NUM) {
            ep2->v.num = val;
            ep2->sibling->v.tick = -1;
            return;
        }
    }
                                        /* hand build definition */
    ep1 = newnode();
    ep1->type = '=';
    ep2 = newnode();
    ep2->type = SYM;
    ep2->v.name = savestr(vname);
    addekid(ep1, ep2);
    ep2 = newnode();
    ep2->type = NUM;
    ep2->v.num = val;
    addekid(ep1, ep2);
    ep2 = newnode();
    ep2->type = TICK;
    ep2->v.tick = -1;
    addekid(ep1, ep2);
    ep2 = newnode();
    ep2->type = NUM;
    addekid(ep1, ep2);
    dclear(vname);
    dpush(ep1);
}


dclear(name)                    /* delete all definitions of name */
char  *name;
{
    register EPNODE  *ep;

    while ((ep = dpop(name)) != NULL)
        epfree(ep);
}


vardefined(name)        /* return non-zero if variable defined */
char  *name;
{
    register EPNODE  *dp;

    return((dp = dlookup(name)) != NULL && dp->v.kid->type == SYM);
}


#ifdef  OUTCHAN
chanout()                       /* set output channels */
{
    register EPNODE  *ep;

    for (ep = outchan; ep != NULL; ep = ep->sibling)
        chanset(ep->v.kid->v.chan, evalue(ep->v.kid->sibling));

}
#endif


dclearall()                     /* clear all definitions */
{
    register int  i;
    register VARDEF  *vp;
    register EPNODE  *ep;

    for (i = 0; i < NHASH; i++)
        for (vp = hashtbl[i]; vp != NULL; vp = vp->next)
            dclear(vp->name);
#ifdef  OUTCHAN
    for (ep = outchan; ep != NULL; ep = ep->sibling)
        epfree(ep);
    outchan = NULL;
#endif
}


EPNODE *
dlookup(name)                   /* look up a definition */
char  *name;
{
    register VARDEF  *vp;
    
    if ((vp = varlookup(name)) == NULL)
        return(NULL);
    return(vp->def);
}


VARDEF *
varlookup(name)                 /* look up a variable */
char  *name;
{
    register VARDEF  *vp;
    
    for (vp = hashtbl[hash(name)]; vp != NULL; vp = vp->next)
        if (!strcmp(vp->name, name))
            return(vp);
    return(NULL);
}


VARDEF *
varinsert(name)                 /* get a link to a variable */
char  *name;
{
    register VARDEF  *vp;
    int  hv;
    
    hv = hash(name);
    for (vp = hashtbl[hv]; vp != NULL; vp = vp->next)
        if (!strcmp(vp->name, name)) {
            vp->nlinks++;
            return(vp);
        }
    vp = (VARDEF *)emalloc(sizeof(VARDEF));
    vp->name = savestr(name);
    vp->nlinks = 1;
    vp->def = NULL;
    vp->lib = NULL;
    vp->next = hashtbl[hv];
    hashtbl[hv] = vp;
    return(vp);
}


varfree(ln)                             /* release link to variable */
register VARDEF  *ln;
{
    register VARDEF  *vp;
    int  hv;

    if (--ln->nlinks > 0)
        return;                         /* still active */

    hv = hash(ln->name);
    vp = hashtbl[hv];
    if (vp == ln)
        hashtbl[hv] = vp->next;
    else {
        while (vp->next != ln)          /* must be in list */
                vp = vp->next;
        vp->next = ln->next;
    }
    freestr(ln->name);
    efree((char *)ln);
}


EPNODE *
dfirst()                        /* return pointer to first definition */
{
    htndx = 0;
    htpos = NULL;
#ifdef  OUTCHAN
    ochpos = outchan;
#endif
    return(dnext());
}


EPNODE *
dnext()                         /* return pointer to next definition */
{
    register EPNODE  *ep;

    while (htndx < NHASH) {
        if (htpos == NULL)
                htpos = hashtbl[htndx++];
        while (htpos != NULL) {
            ep = htpos->def;
            htpos = htpos->next;
            if (ep != NULL)
                return(ep);
        }
    }
#ifdef  OUTCHAN
    if ((ep = ochpos) != NULL)
        ochpos = ep->sibling;
    return(ep);
#else
    return(NULL);
#endif
}


EPNODE *
dpop(name)                      /* pop a definition */
char  *name;
{
    register VARDEF  *vp;
    register EPNODE  *dp;
    
    if ((vp = varlookup(name)) == NULL || vp->def == NULL)
        return(NULL);
    dp = vp->def;
    vp->def = dp->sibling;
    varfree(vp);
    return(dp);
}


dpush(ep)                       /* push on a definition */
register EPNODE  *ep;
{
    register VARDEF  *vp;

    vp = varinsert(dname(ep));
    ep->sibling = vp->def;
    vp->def = ep;
}


#ifdef  OUTCHAN
addchan(sp)                     /* add an output channel assignment */
EPNODE  *sp;
{
    int  ch = sp->v.kid->v.chan;
    register EPNODE  *ep, *epl;

    for (epl = NULL, ep = outchan; ep != NULL; epl = ep, ep = ep->sibling)
        if (ep->v.kid->v.chan >= ch) {
            if (epl != NULL)
                epl->sibling = sp;
            else
                outchan = sp;
            if (ep->v.kid->v.chan > ch)
                sp->sibling = ep;
            else {
                sp->sibling = ep->sibling;
                epfree(ep);
            }
            return;
        }
    if (epl != NULL)
        epl->sibling = sp;
    else
        outchan = sp;
    sp->sibling = NULL;

}
#endif


loaddefn()                      /* load next definition */
{
    register EPNODE  *ep;

    if (nextc == ';') {         /* empty statement */
        scan();
        return;
    }
#ifdef  OUTCHAN
    if (nextc == '$') {         /* channel assignment */
        ep = getchan();
        addchan(ep);
    } else
#endif
    {                           /* ordinary definition */
        ep = getdefn();
#ifdef  REDEFW
        if (dlookup(dname(ep)) != NULL) {
                dclear(dname(ep));
                wputs(dname(ep));
                wputs(": redefined\n");
        }
#else
        dclear(dname(ep));
#endif
        dpush(ep);
    }
    if (nextc != EOF) {
        if (nextc != ';')
            syntax("';' expected");
        scan();
    }
}


EPNODE *
getdefn()                       /* A -> SYM = E1 */
                                /*      FUNC(SYM,..) = E1 */
{
    register EPNODE  *ep1, *ep2;

    if (!isalpha(nextc))
        syntax("illegal variable name");

    ep1 = newnode();
    ep1->type = SYM;
    ep1->v.name = savestr(getname());

#ifdef  FUNCTION
    if (nextc == '(') {
        ep2 = newnode();
        ep2->type = FUNC;
        addekid(ep2, ep1);
        ep1 = ep2;
        do {
            scan();
            if (!isalpha(nextc))
                syntax("illegal variable name");
            ep2 = newnode();
            ep2->type = SYM;
            ep2->v.name = savestr(getname());
            addekid(ep1, ep2);
        } while (nextc == ',');
        if (nextc != ')')
            syntax("')' expected");
        scan();
        curfunc = ep1;
    } else
        curfunc = NULL;
#endif

    if (nextc != '=')
        syntax("'=' expected");
    scan();

    ep2 = newnode();
    ep2->type = '=';
    addekid(ep2, ep1);
    addekid(ep2, getE1());

#ifdef  FUNCTION
    if (ep1->type == SYM)
#endif
    {
        ep1 = newnode();
        ep1->type = TICK;
        ep1->v.tick = -1;
        addekid(ep2, ep1);
        ep1 = newnode();
        ep1->type = NUM;
        addekid(ep2, ep1);
    }

    return(ep2);
}


#ifdef  OUTCHAN
EPNODE *
getchan()                       /* A -> $N = E1 */
{
    register EPNODE  *ep1, *ep2;

    if (nextc != '$')
        syntax("missing '$'");
    scan();

    ep1 = newnode();
    ep1->type = CHAN;
    ep1->v.chan = getinum();

    if (nextc != '=')
        syntax("'=' expected");
    scan();

    ep2 = newnode();
    ep2->type = '=';
    addekid(ep2, ep1);
    addekid(ep2, getE1());

    return(ep2);
}
#endif


/*
 *  The following routines are for internal use only:
 */


static double
dvalue(name, d)                 /* evaluate a variable */
char  *name;
EPNODE  *d;
{
    register EPNODE  *ep1, *ep2;
    
    if (d == NULL || d->v.kid->type != SYM) {
        eputs(name);
        eputs(": undefined variable\n");
        quit(1);
    }
    ep1 = d->v.kid->sibling;                    /* get expression */
    ep2 = ep1->sibling;                         /* check time */
    if (ep2->v.tick < 0 || ep2->v.tick < eclock) {
        ep2->v.tick = eclock;
        ep2 = ep2->sibling;
        ep2->v.num = evalue(ep1);               /* compute new value */
    } else
        ep2 = ep2->sibling;                     /* reuse old value */

    return(ep2->v.num);
}


static int
hash(s)                         /* hash a string */
register char  *s;
{
    register int  rval = 0;

    while (*s)
        rval += *s++;
    
    return(rval % NHASH);
}
Revision:	1.2
Committed:	Thu May 31 10:24:28 1990 UTC (35 years, 5 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 1.1:	+10 -0 lines
Log Message:	added conditional compiles for redefinition warning (REDEFW)
#	User	Rev	Content
1	greg	1.1	/* Copyright (c) 1986 Regents of the University of California */
2
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* Store variable definitions.
9			*
10			* 7/1/85 Greg Ward
11			*
12			* 11/11/85 Added conditional compiles (OUTCHAN) for control output.
13			*
14			* 4/2/86 Added conditional compiles for function definitions (FUNCTION).
15			*
16			* 1/15/88 Added clock for caching of variable values.
17			*
18			* 11/16/88 Added VARDEF structure for hard linking.
19	greg	1.2	*
20			* 5/31/90 Added conditional compile (REDEFW) for redefinition warning.
21	greg	1.1	*/
22
23			#include <stdio.h>
24
25			#include <ctype.h>
26
27			#include "calcomp.h"
28
29			#ifndef NHASH
30			#define NHASH 521 /* hash size (a prime!) */
31			#endif
32
33			#define newnode() (EPNODE *)ecalloc(1, sizeof(EPNODE))
34
35			extern char ecalloc(), savestr();
36
37			extern double dvalue();
38
39			long eclock = -1; /* value storage timer */
40
41			static VARDEF hashtbl[NHASH]; / definition list */
42			static int htndx; /* index for */
43			static VARDEF htpos; / ...dfirst() and */
44			#ifdef OUTCHAN
45			static EPNODE ochpos; / ...dnext */
46			static EPNODE *outchan;
47			#endif
48
49			#ifdef FUNCTION
50			EPNODE *curfunc;
51			#define dname(ep) ((ep)->v.kid->type == SYM ? \
52			(ep)->v.kid->v.name : \
53			(ep)->v.kid->v.kid->v.name)
54			#else
55			#define dname(ep) ((ep)->v.kid->v.name)
56			#endif
57
58
59			fcompile(fname) /* get definitions from a file */
60			char *fname;
61			{
62			FILE *fp;
63
64			if (fname == NULL)
65			fp = stdin;
66			else if ((fp = fopen(fname, "r")) == NULL) {
67			eputs(fname);
68			eputs(": cannot open\n");
69			quit(1);
70			}
71			initfile(fname, fp);
72			while (nextc != EOF)
73			loaddefn();
74			if (fname != NULL)
75			fclose(fp);
76			}
77
78
79			scompile(file, str) /* get definitions from a string */
80			char *file;
81			char *str;
82			{
83			initstr(file, str);
84			while (nextc != EOF)
85			loaddefn();
86			}
87
88
89			double
90			varvalue(vname) /* return a variable's value */
91			char *vname;
92			{
93			return(dvalue(vname, dlookup(vname)));
94			}
95
96
97			double
98			evariable(ep) /* evaluate a variable */
99			EPNODE *ep;
100			{
101			register VARDEF *dp = ep->v.ln;
102
103			return(dvalue(dp->name, dp->def));
104			}
105
106
107			varset(vname, val) /* set a variable's value */
108			char *vname;
109			double val;
110			{
111			register EPNODE ep1, ep2;
112			/* check for quick set */
113			if ((ep1 = dlookup(vname)) != NULL && ep1->v.kid->type == SYM) {
114			ep2 = ep1->v.kid->sibling;
115			if (ep2->type == NUM) {
116			ep2->v.num = val;
117			ep2->sibling->v.tick = -1;
118			return;
119			}
120			}
121			/* hand build definition */
122			ep1 = newnode();
123			ep1->type = '=';
124			ep2 = newnode();
125			ep2->type = SYM;
126			ep2->v.name = savestr(vname);
127			addekid(ep1, ep2);
128			ep2 = newnode();
129			ep2->type = NUM;
130			ep2->v.num = val;
131			addekid(ep1, ep2);
132			ep2 = newnode();
133			ep2->type = TICK;
134			ep2->v.tick = -1;
135			addekid(ep1, ep2);
136			ep2 = newnode();
137			ep2->type = NUM;
138			addekid(ep1, ep2);
139			dclear(vname);
140			dpush(ep1);
141			}
142
143
144			dclear(name) /* delete all definitions of name */
145			char *name;
146			{
147			register EPNODE *ep;
148
149			while ((ep = dpop(name)) != NULL)
150			epfree(ep);
151			}
152
153
154			vardefined(name) /* return non-zero if variable defined */
155			char *name;
156			{
157			register EPNODE *dp;
158
159			return((dp = dlookup(name)) != NULL && dp->v.kid->type == SYM);
160			}
161
162
163			#ifdef OUTCHAN
164			chanout() /* set output channels */
165			{
166			register EPNODE *ep;
167
168			for (ep = outchan; ep != NULL; ep = ep->sibling)
169			chanset(ep->v.kid->v.chan, evalue(ep->v.kid->sibling));
170
171			}
172			#endif
173
174
175			dclearall() /* clear all definitions */
176			{
177			register int i;
178			register VARDEF *vp;
179			register EPNODE *ep;
180
181			for (i = 0; i < NHASH; i++)
182			for (vp = hashtbl[i]; vp != NULL; vp = vp->next)
183			dclear(vp->name);
184			#ifdef OUTCHAN
185			for (ep = outchan; ep != NULL; ep = ep->sibling)
186			epfree(ep);
187			outchan = NULL;
188			#endif
189			}
190
191
192			EPNODE *
193			dlookup(name) /* look up a definition */
194			char *name;
195			{
196			register VARDEF *vp;
197
198			if ((vp = varlookup(name)) == NULL)
199			return(NULL);
200			return(vp->def);
201			}
202
203
204			VARDEF *
205			varlookup(name) /* look up a variable */
206			char *name;
207			{
208			register VARDEF *vp;
209
210			for (vp = hashtbl[hash(name)]; vp != NULL; vp = vp->next)
211			if (!strcmp(vp->name, name))
212			return(vp);
213			return(NULL);
214			}
215
216
217			VARDEF *
218			varinsert(name) /* get a link to a variable */
219			char *name;
220			{
221			register VARDEF *vp;
222			int hv;
223
224			hv = hash(name);
225			for (vp = hashtbl[hv]; vp != NULL; vp = vp->next)
226			if (!strcmp(vp->name, name)) {
227			vp->nlinks++;
228			return(vp);
229			}
230			vp = (VARDEF *)emalloc(sizeof(VARDEF));
231			vp->name = savestr(name);
232			vp->nlinks = 1;
233			vp->def = NULL;
234			vp->lib = NULL;
235			vp->next = hashtbl[hv];
236			hashtbl[hv] = vp;
237			return(vp);
238			}
239
240
241			varfree(ln) /* release link to variable */
242			register VARDEF *ln;
243			{
244			register VARDEF *vp;
245			int hv;
246
247			if (--ln->nlinks > 0)
248			return; /* still active */
249
250			hv = hash(ln->name);
251			vp = hashtbl[hv];
252			if (vp == ln)
253			hashtbl[hv] = vp->next;
254			else {
255			while (vp->next != ln) /* must be in list */
256			vp = vp->next;
257			vp->next = ln->next;
258			}
259			freestr(ln->name);
260			efree((char *)ln);
261			}
262
263
264			EPNODE *
265			dfirst() /* return pointer to first definition */
266			{
267			htndx = 0;
268			htpos = NULL;
269			#ifdef OUTCHAN
270			ochpos = outchan;
271			#endif
272			return(dnext());
273			}
274
275
276			EPNODE *
277			dnext() /* return pointer to next definition */
278			{
279			register EPNODE *ep;
280
281			while (htndx < NHASH) {
282			if (htpos == NULL)
283			htpos = hashtbl[htndx++];
284			while (htpos != NULL) {
285			ep = htpos->def;
286			htpos = htpos->next;
287			if (ep != NULL)
288			return(ep);
289			}
290			}
291			#ifdef OUTCHAN
292			if ((ep = ochpos) != NULL)
293			ochpos = ep->sibling;
294			return(ep);
295			#else
296			return(NULL);
297			#endif
298			}
299
300
301			EPNODE *
302			dpop(name) /* pop a definition */
303			char *name;
304			{
305			register VARDEF *vp;
306			register EPNODE *dp;
307
308			if ((vp = varlookup(name)) == NULL \|\| vp->def == NULL)
309			return(NULL);
310			dp = vp->def;
311			vp->def = dp->sibling;
312			varfree(vp);
313			return(dp);
314			}
315
316
317			dpush(ep) /* push on a definition */
318			register EPNODE *ep;
319			{
320			register VARDEF *vp;
321
322			vp = varinsert(dname(ep));
323			ep->sibling = vp->def;
324			vp->def = ep;
325			}
326
327
328			#ifdef OUTCHAN
329			addchan(sp) /* add an output channel assignment */
330			EPNODE *sp;
331			{
332			int ch = sp->v.kid->v.chan;
333			register EPNODE ep, epl;
334
335			for (epl = NULL, ep = outchan; ep != NULL; epl = ep, ep = ep->sibling)
336			if (ep->v.kid->v.chan >= ch) {
337			if (epl != NULL)
338			epl->sibling = sp;
339			else
340			outchan = sp;
341			if (ep->v.kid->v.chan > ch)
342			sp->sibling = ep;
343			else {
344			sp->sibling = ep->sibling;
345			epfree(ep);
346			}
347			return;
348			}
349			if (epl != NULL)
350			epl->sibling = sp;
351			else
352			outchan = sp;
353			sp->sibling = NULL;
354
355			}
356			#endif
357
358
359			loaddefn() /* load next definition */
360			{
361			register EPNODE *ep;
362
363			if (nextc == ';') { /* empty statement */
364			scan();
365			return;
366			}
367			#ifdef OUTCHAN
368			if (nextc == '$') { /* channel assignment */
369			ep = getchan();
370			addchan(ep);
371			} else
372			#endif
373			{ /* ordinary definition */
374			ep = getdefn();
375	greg	1.2	#ifdef REDEFW
376			if (dlookup(dname(ep)) != NULL) {
377			dclear(dname(ep));
378			wputs(dname(ep));
379			wputs(": redefined\n");
380			}
381			#else
382	greg	1.1	dclear(dname(ep));
383	greg	1.2	#endif
384	greg	1.1	dpush(ep);
385			}
386			if (nextc != EOF) {
387			if (nextc != ';')
388			syntax("';' expected");
389			scan();
390			}
391			}
392
393
394			EPNODE *
395			getdefn() /* A -> SYM = E1 */
396			/* FUNC(SYM,..) = E1 */
397			{
398			register EPNODE ep1, ep2;
399
400			if (!isalpha(nextc))
401			syntax("illegal variable name");
402
403			ep1 = newnode();
404			ep1->type = SYM;
405			ep1->v.name = savestr(getname());
406
407			#ifdef FUNCTION
408			if (nextc == '(') {
409			ep2 = newnode();
410			ep2->type = FUNC;
411			addekid(ep2, ep1);
412			ep1 = ep2;
413			do {
414			scan();
415			if (!isalpha(nextc))
416			syntax("illegal variable name");
417			ep2 = newnode();
418			ep2->type = SYM;
419			ep2->v.name = savestr(getname());
420			addekid(ep1, ep2);
421			} while (nextc == ',');
422			if (nextc != ')')
423			syntax("')' expected");
424			scan();
425			curfunc = ep1;
426			} else
427			curfunc = NULL;
428			#endif
429
430			if (nextc != '=')
431			syntax("'=' expected");
432			scan();
433
434			ep2 = newnode();
435			ep2->type = '=';
436			addekid(ep2, ep1);
437			addekid(ep2, getE1());
438
439			#ifdef FUNCTION
440			if (ep1->type == SYM)
441			#endif
442			{
443			ep1 = newnode();
444			ep1->type = TICK;
445			ep1->v.tick = -1;
446			addekid(ep2, ep1);
447			ep1 = newnode();
448			ep1->type = NUM;
449			addekid(ep2, ep1);
450			}
451
452			return(ep2);
453			}
454
455
456			#ifdef OUTCHAN
457			EPNODE *
458			getchan() /* A -> $N = E1 */
459			{
460			register EPNODE ep1, ep2;
461
462			if (nextc != '$')
463			syntax("missing '$'");
464			scan();
465
466			ep1 = newnode();
467			ep1->type = CHAN;
468			ep1->v.chan = getinum();
469
470			if (nextc != '=')
471			syntax("'=' expected");
472			scan();
473
474			ep2 = newnode();
475			ep2->type = '=';
476			addekid(ep2, ep1);
477			addekid(ep2, getE1());
478
479			return(ep2);
480			}
481			#endif
482
483
484
485			/*
486			* The following routines are for internal use only:
487			*/
488
489
490			static double
491			dvalue(name, d) /* evaluate a variable */
492			char *name;
493			EPNODE *d;
494			{
495			register EPNODE ep1, ep2;
496
497			if (d == NULL \|\| d->v.kid->type != SYM) {
498			eputs(name);
499			eputs(": undefined variable\n");
500			quit(1);
501			}
502			ep1 = d->v.kid->sibling; /* get expression */
503			ep2 = ep1->sibling; /* check time */
504			if (ep2->v.tick < 0 \|\| ep2->v.tick < eclock) {
505			ep2->v.tick = eclock;
506			ep2 = ep2->sibling;
507			ep2->v.num = evalue(ep1); /* compute new value */
508			} else
509			ep2 = ep2->sibling; /* reuse old value */
510
511			return(ep2->v.num);
512			}
513
514
515			static int
516			hash(s) /* hash a string */
517			register char *s;
518			{
519			register int rval = 0;
520
521			while (*s)
522			rval += *s++;
523
524			return(rval % NHASH);
525			}