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();

static 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(fp, fname, 0);
    while (nextc != EOF)
        loaddefn();
    if (fname != NULL)
        fclose(fp);
}


scompile(str, fn, ln)           /* get definitions from a string */
char  *str;
char  *fn;
int  ln;
{
    initstr(str, fn, ln);
    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;
            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);
    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(cs)                     /* set output channels */
int  (*cs)();
{
    register EPNODE  *ep;

    for (ep = outchan; ep != NULL; ep = ep->sibling)
        (*cs)(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());

    if (
#ifdef  FUNCTION
            ep1->type == SYM &&
#endif
            ep1->sibling->type != NUM) {
        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 */
    if (ep1->type == NUM)
        return(ep1->v.num);                     /* return if number */
    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);               /* needs new value */
    } else
        ep2 = ep2->sibling;                     /* else 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:	1.7
Committed:	Fri Jul 20 08:30:23 1990 UTC (33 years, 9 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 1.6:	+3 -2 lines
Log Message:	forgot addition for elimination of TICK for numeric def'ns
#	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	greg	1.3	static double dvalue();
38	greg	1.1
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	greg	1.4	initfile(fp, fname, 0);
72	greg	1.1	while (nextc != EOF)
73			loaddefn();
74			if (fname != NULL)
75			fclose(fp);
76			}
77
78
79	greg	1.4	scompile(str, fn, ln) /* get definitions from a string */
80	greg	1.1	char *str;
81	greg	1.4	char *fn;
82			int ln;
83	greg	1.1	{
84	greg	1.4	initstr(str, fn, ln);
85	greg	1.1	while (nextc != EOF)
86			loaddefn();
87			}
88
89
90			double
91			varvalue(vname) /* return a variable's value */
92			char *vname;
93			{
94			return(dvalue(vname, dlookup(vname)));
95			}
96
97
98			double
99			evariable(ep) /* evaluate a variable */
100			EPNODE *ep;
101			{
102			register VARDEF *dp = ep->v.ln;
103
104			return(dvalue(dp->name, dp->def));
105			}
106
107
108			varset(vname, val) /* set a variable's value */
109			char *vname;
110			double val;
111			{
112			register EPNODE ep1, ep2;
113			/* check for quick set */
114			if ((ep1 = dlookup(vname)) != NULL && ep1->v.kid->type == SYM) {
115			ep2 = ep1->v.kid->sibling;
116			if (ep2->type == NUM) {
117			ep2->v.num = val;
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			dclear(vname);
133			dpush(ep1);
134			}
135
136
137			dclear(name) /* delete all definitions of name */
138			char *name;
139			{
140			register EPNODE *ep;
141
142			while ((ep = dpop(name)) != NULL)
143			epfree(ep);
144			}
145
146
147			vardefined(name) /* return non-zero if variable defined */
148			char *name;
149			{
150			register EPNODE *dp;
151
152			return((dp = dlookup(name)) != NULL && dp->v.kid->type == SYM);
153			}
154
155
156			#ifdef OUTCHAN
157	greg	1.6	chanout(cs) /* set output channels */
158			int (*cs)();
159	greg	1.1	{
160			register EPNODE *ep;
161
162			for (ep = outchan; ep != NULL; ep = ep->sibling)
163	greg	1.6	(*cs)(ep->v.kid->v.chan, evalue(ep->v.kid->sibling));
164	greg	1.1
165			}
166			#endif
167
168
169			dclearall() /* clear all definitions */
170			{
171			register int i;
172			register VARDEF *vp;
173			register EPNODE *ep;
174
175			for (i = 0; i < NHASH; i++)
176			for (vp = hashtbl[i]; vp != NULL; vp = vp->next)
177			dclear(vp->name);
178			#ifdef OUTCHAN
179			for (ep = outchan; ep != NULL; ep = ep->sibling)
180			epfree(ep);
181			outchan = NULL;
182			#endif
183			}
184
185
186			EPNODE *
187			dlookup(name) /* look up a definition */
188			char *name;
189			{
190			register VARDEF *vp;
191
192			if ((vp = varlookup(name)) == NULL)
193			return(NULL);
194			return(vp->def);
195			}
196
197
198			VARDEF *
199			varlookup(name) /* look up a variable */
200			char *name;
201			{
202			register VARDEF *vp;
203
204			for (vp = hashtbl[hash(name)]; vp != NULL; vp = vp->next)
205			if (!strcmp(vp->name, name))
206			return(vp);
207			return(NULL);
208			}
209
210
211			VARDEF *
212			varinsert(name) /* get a link to a variable */
213			char *name;
214			{
215			register VARDEF *vp;
216			int hv;
217
218			hv = hash(name);
219			for (vp = hashtbl[hv]; vp != NULL; vp = vp->next)
220			if (!strcmp(vp->name, name)) {
221			vp->nlinks++;
222			return(vp);
223			}
224			vp = (VARDEF *)emalloc(sizeof(VARDEF));
225			vp->name = savestr(name);
226			vp->nlinks = 1;
227			vp->def = NULL;
228			vp->lib = NULL;
229			vp->next = hashtbl[hv];
230			hashtbl[hv] = vp;
231			return(vp);
232			}
233
234
235			varfree(ln) /* release link to variable */
236			register VARDEF *ln;
237			{
238			register VARDEF *vp;
239			int hv;
240
241			if (--ln->nlinks > 0)
242			return; /* still active */
243
244			hv = hash(ln->name);
245			vp = hashtbl[hv];
246			if (vp == ln)
247			hashtbl[hv] = vp->next;
248			else {
249			while (vp->next != ln) /* must be in list */
250			vp = vp->next;
251			vp->next = ln->next;
252			}
253			freestr(ln->name);
254			efree((char *)ln);
255			}
256
257
258			EPNODE *
259			dfirst() /* return pointer to first definition */
260			{
261			htndx = 0;
262			htpos = NULL;
263			#ifdef OUTCHAN
264			ochpos = outchan;
265			#endif
266			return(dnext());
267			}
268
269
270			EPNODE *
271			dnext() /* return pointer to next definition */
272			{
273			register EPNODE *ep;
274
275			while (htndx < NHASH) {
276			if (htpos == NULL)
277			htpos = hashtbl[htndx++];
278			while (htpos != NULL) {
279			ep = htpos->def;
280			htpos = htpos->next;
281			if (ep != NULL)
282			return(ep);
283			}
284			}
285			#ifdef OUTCHAN
286			if ((ep = ochpos) != NULL)
287			ochpos = ep->sibling;
288			return(ep);
289			#else
290			return(NULL);
291			#endif
292			}
293
294
295			EPNODE *
296			dpop(name) /* pop a definition */
297			char *name;
298			{
299			register VARDEF *vp;
300			register EPNODE *dp;
301
302			if ((vp = varlookup(name)) == NULL \|\| vp->def == NULL)
303			return(NULL);
304			dp = vp->def;
305			vp->def = dp->sibling;
306			varfree(vp);
307			return(dp);
308			}
309
310
311			dpush(ep) /* push on a definition */
312			register EPNODE *ep;
313			{
314			register VARDEF *vp;
315
316			vp = varinsert(dname(ep));
317			ep->sibling = vp->def;
318			vp->def = ep;
319			}
320
321
322			#ifdef OUTCHAN
323			addchan(sp) /* add an output channel assignment */
324			EPNODE *sp;
325			{
326			int ch = sp->v.kid->v.chan;
327			register EPNODE ep, epl;
328
329			for (epl = NULL, ep = outchan; ep != NULL; epl = ep, ep = ep->sibling)
330			if (ep->v.kid->v.chan >= ch) {
331			if (epl != NULL)
332			epl->sibling = sp;
333			else
334			outchan = sp;
335			if (ep->v.kid->v.chan > ch)
336			sp->sibling = ep;
337			else {
338			sp->sibling = ep->sibling;
339			epfree(ep);
340			}
341			return;
342			}
343			if (epl != NULL)
344			epl->sibling = sp;
345			else
346			outchan = sp;
347			sp->sibling = NULL;
348
349			}
350			#endif
351
352
353			loaddefn() /* load next definition */
354			{
355			register EPNODE *ep;
356
357			if (nextc == ';') { /* empty statement */
358			scan();
359			return;
360			}
361			#ifdef OUTCHAN
362			if (nextc == '$') { /* channel assignment */
363			ep = getchan();
364			addchan(ep);
365			} else
366			#endif
367			{ /* ordinary definition */
368			ep = getdefn();
369	greg	1.2	#ifdef REDEFW
370			if (dlookup(dname(ep)) != NULL) {
371			dclear(dname(ep));
372			wputs(dname(ep));
373			wputs(": redefined\n");
374			}
375			#else
376	greg	1.1	dclear(dname(ep));
377	greg	1.2	#endif
378	greg	1.1	dpush(ep);
379			}
380			if (nextc != EOF) {
381			if (nextc != ';')
382			syntax("';' expected");
383			scan();
384			}
385			}
386
387
388			EPNODE *
389			getdefn() /* A -> SYM = E1 */
390			/* FUNC(SYM,..) = E1 */
391			{
392			register EPNODE ep1, ep2;
393
394			if (!isalpha(nextc))
395			syntax("illegal variable name");
396
397			ep1 = newnode();
398			ep1->type = SYM;
399			ep1->v.name = savestr(getname());
400
401			#ifdef FUNCTION
402			if (nextc == '(') {
403			ep2 = newnode();
404			ep2->type = FUNC;
405			addekid(ep2, ep1);
406			ep1 = ep2;
407			do {
408			scan();
409			if (!isalpha(nextc))
410			syntax("illegal variable name");
411			ep2 = newnode();
412			ep2->type = SYM;
413			ep2->v.name = savestr(getname());
414			addekid(ep1, ep2);
415			} while (nextc == ',');
416			if (nextc != ')')
417			syntax("')' expected");
418			scan();
419			curfunc = ep1;
420			} else
421			curfunc = NULL;
422			#endif
423
424			if (nextc != '=')
425			syntax("'=' expected");
426			scan();
427
428			ep2 = newnode();
429			ep2->type = '=';
430			addekid(ep2, ep1);
431			addekid(ep2, getE1());
432
433	greg	1.7	if (
434	greg	1.1	#ifdef FUNCTION
435	greg	1.7	ep1->type == SYM &&
436	greg	1.1	#endif
437	greg	1.7	ep1->sibling->type != NUM) {
438	greg	1.1	ep1 = newnode();
439			ep1->type = TICK;
440			ep1->v.tick = -1;
441			addekid(ep2, ep1);
442			ep1 = newnode();
443			ep1->type = NUM;
444			addekid(ep2, ep1);
445			}
446
447			return(ep2);
448			}
449
450
451			#ifdef OUTCHAN
452			EPNODE *
453			getchan() /* A -> $N = E1 */
454			{
455			register EPNODE ep1, ep2;
456
457			if (nextc != '$')
458			syntax("missing '$'");
459			scan();
460
461			ep1 = newnode();
462			ep1->type = CHAN;
463			ep1->v.chan = getinum();
464
465			if (nextc != '=')
466			syntax("'=' expected");
467			scan();
468
469			ep2 = newnode();
470			ep2->type = '=';
471			addekid(ep2, ep1);
472			addekid(ep2, getE1());
473
474			return(ep2);
475			}
476			#endif
477
478
479
480			/*
481			* The following routines are for internal use only:
482			*/
483
484
485			static double
486			dvalue(name, d) /* evaluate a variable */
487			char *name;
488			EPNODE *d;
489			{
490			register EPNODE ep1, ep2;
491
492			if (d == NULL \|\| d->v.kid->type != SYM) {
493			eputs(name);
494			eputs(": undefined variable\n");
495			quit(1);
496			}
497			ep1 = d->v.kid->sibling; /* get expression */
498	greg	1.5	if (ep1->type == NUM)
499			return(ep1->v.num); /* return if number */
500	greg	1.1	ep2 = ep1->sibling; /* check time */
501			if (ep2->v.tick < 0 \|\| ep2->v.tick < eclock) {
502			ep2->v.tick = eclock;
503			ep2 = ep2->sibling;
504	greg	1.5	ep2->v.num = evalue(ep1); /* needs new value */
505	greg	1.1	} else
506	greg	1.5	ep2 = ep2->sibling; /* else reuse old value */
507	greg	1.1
508			return(ep2->v.num);
509			}
510
511
512			static int
513			hash(s) /* hash a string */
514			register char *s;
515			{
516			register int rval = 0;
517
518			while (*s)
519			rval += *s++;
520
521			return(rval % NHASH);
522			}