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;
            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:	1.4
Committed:	Thu Jul 19 11:06:37 1990 UTC (33 years, 9 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 1.3:	+5 -4 lines
Log Message:	added line numbers to error reports
#	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			ep2->sibling->v.tick = -1;
119			return;
120			}
121			}
122			/* hand build definition */
123			ep1 = newnode();
124			ep1->type = '=';
125			ep2 = newnode();
126			ep2->type = SYM;
127			ep2->v.name = savestr(vname);
128			addekid(ep1, ep2);
129			ep2 = newnode();
130			ep2->type = NUM;
131			ep2->v.num = val;
132			addekid(ep1, ep2);
133			ep2 = newnode();
134			ep2->type = TICK;
135			ep2->v.tick = -1;
136			addekid(ep1, ep2);
137			ep2 = newnode();
138			ep2->type = NUM;
139			addekid(ep1, ep2);
140			dclear(vname);
141			dpush(ep1);
142			}
143
144
145			dclear(name) /* delete all definitions of name */
146			char *name;
147			{
148			register EPNODE *ep;
149
150			while ((ep = dpop(name)) != NULL)
151			epfree(ep);
152			}
153
154
155			vardefined(name) /* return non-zero if variable defined */
156			char *name;
157			{
158			register EPNODE *dp;
159
160			return((dp = dlookup(name)) != NULL && dp->v.kid->type == SYM);
161			}
162
163
164			#ifdef OUTCHAN
165			chanout() /* set output channels */
166			{
167			register EPNODE *ep;
168
169			for (ep = outchan; ep != NULL; ep = ep->sibling)
170			chanset(ep->v.kid->v.chan, evalue(ep->v.kid->sibling));
171
172			}
173			#endif
174
175
176			dclearall() /* clear all definitions */
177			{
178			register int i;
179			register VARDEF *vp;
180			register EPNODE *ep;
181
182			for (i = 0; i < NHASH; i++)
183			for (vp = hashtbl[i]; vp != NULL; vp = vp->next)
184			dclear(vp->name);
185			#ifdef OUTCHAN
186			for (ep = outchan; ep != NULL; ep = ep->sibling)
187			epfree(ep);
188			outchan = NULL;
189			#endif
190			}
191
192
193			EPNODE *
194			dlookup(name) /* look up a definition */
195			char *name;
196			{
197			register VARDEF *vp;
198
199			if ((vp = varlookup(name)) == NULL)
200			return(NULL);
201			return(vp->def);
202			}
203
204
205			VARDEF *
206			varlookup(name) /* look up a variable */
207			char *name;
208			{
209			register VARDEF *vp;
210
211			for (vp = hashtbl[hash(name)]; vp != NULL; vp = vp->next)
212			if (!strcmp(vp->name, name))
213			return(vp);
214			return(NULL);
215			}
216
217
218			VARDEF *
219			varinsert(name) /* get a link to a variable */
220			char *name;
221			{
222			register VARDEF *vp;
223			int hv;
224
225			hv = hash(name);
226			for (vp = hashtbl[hv]; vp != NULL; vp = vp->next)
227			if (!strcmp(vp->name, name)) {
228			vp->nlinks++;
229			return(vp);
230			}
231			vp = (VARDEF *)emalloc(sizeof(VARDEF));
232			vp->name = savestr(name);
233			vp->nlinks = 1;
234			vp->def = NULL;
235			vp->lib = NULL;
236			vp->next = hashtbl[hv];
237			hashtbl[hv] = vp;
238			return(vp);
239			}
240
241
242			varfree(ln) /* release link to variable */
243			register VARDEF *ln;
244			{
245			register VARDEF *vp;
246			int hv;
247
248			if (--ln->nlinks > 0)
249			return; /* still active */
250
251			hv = hash(ln->name);
252			vp = hashtbl[hv];
253			if (vp == ln)
254			hashtbl[hv] = vp->next;
255			else {
256			while (vp->next != ln) /* must be in list */
257			vp = vp->next;
258			vp->next = ln->next;
259			}
260			freestr(ln->name);
261			efree((char *)ln);
262			}
263
264
265			EPNODE *
266			dfirst() /* return pointer to first definition */
267			{
268			htndx = 0;
269			htpos = NULL;
270			#ifdef OUTCHAN
271			ochpos = outchan;
272			#endif
273			return(dnext());
274			}
275
276
277			EPNODE *
278			dnext() /* return pointer to next definition */
279			{
280			register EPNODE *ep;
281
282			while (htndx < NHASH) {
283			if (htpos == NULL)
284			htpos = hashtbl[htndx++];
285			while (htpos != NULL) {
286			ep = htpos->def;
287			htpos = htpos->next;
288			if (ep != NULL)
289			return(ep);
290			}
291			}
292			#ifdef OUTCHAN
293			if ((ep = ochpos) != NULL)
294			ochpos = ep->sibling;
295			return(ep);
296			#else
297			return(NULL);
298			#endif
299			}
300
301
302			EPNODE *
303			dpop(name) /* pop a definition */
304			char *name;
305			{
306			register VARDEF *vp;
307			register EPNODE *dp;
308
309			if ((vp = varlookup(name)) == NULL \|\| vp->def == NULL)
310			return(NULL);
311			dp = vp->def;
312			vp->def = dp->sibling;
313			varfree(vp);
314			return(dp);
315			}
316
317
318			dpush(ep) /* push on a definition */
319			register EPNODE *ep;
320			{
321			register VARDEF *vp;
322
323			vp = varinsert(dname(ep));
324			ep->sibling = vp->def;
325			vp->def = ep;
326			}
327
328
329			#ifdef OUTCHAN
330			addchan(sp) /* add an output channel assignment */
331			EPNODE *sp;
332			{
333			int ch = sp->v.kid->v.chan;
334			register EPNODE ep, epl;
335
336			for (epl = NULL, ep = outchan; ep != NULL; epl = ep, ep = ep->sibling)
337			if (ep->v.kid->v.chan >= ch) {
338			if (epl != NULL)
339			epl->sibling = sp;
340			else
341			outchan = sp;
342			if (ep->v.kid->v.chan > ch)
343			sp->sibling = ep;
344			else {
345			sp->sibling = ep->sibling;
346			epfree(ep);
347			}
348			return;
349			}
350			if (epl != NULL)
351			epl->sibling = sp;
352			else
353			outchan = sp;
354			sp->sibling = NULL;
355
356			}
357			#endif
358
359
360			loaddefn() /* load next definition */
361			{
362			register EPNODE *ep;
363
364			if (nextc == ';') { /* empty statement */
365			scan();
366			return;
367			}
368			#ifdef OUTCHAN
369			if (nextc == '$') { /* channel assignment */
370			ep = getchan();
371			addchan(ep);
372			} else
373			#endif
374			{ /* ordinary definition */
375			ep = getdefn();
376	greg	1.2	#ifdef REDEFW
377			if (dlookup(dname(ep)) != NULL) {
378			dclear(dname(ep));
379			wputs(dname(ep));
380			wputs(": redefined\n");
381			}
382			#else
383	greg	1.1	dclear(dname(ep));
384	greg	1.2	#endif
385	greg	1.1	dpush(ep);
386			}
387			if (nextc != EOF) {
388			if (nextc != ';')
389			syntax("';' expected");
390			scan();
391			}
392			}
393
394
395			EPNODE *
396			getdefn() /* A -> SYM = E1 */
397			/* FUNC(SYM,..) = E1 */
398			{
399			register EPNODE ep1, ep2;
400
401			if (!isalpha(nextc))
402			syntax("illegal variable name");
403
404			ep1 = newnode();
405			ep1->type = SYM;
406			ep1->v.name = savestr(getname());
407
408			#ifdef FUNCTION
409			if (nextc == '(') {
410			ep2 = newnode();
411			ep2->type = FUNC;
412			addekid(ep2, ep1);
413			ep1 = ep2;
414			do {
415			scan();
416			if (!isalpha(nextc))
417			syntax("illegal variable name");
418			ep2 = newnode();
419			ep2->type = SYM;
420			ep2->v.name = savestr(getname());
421			addekid(ep1, ep2);
422			} while (nextc == ',');
423			if (nextc != ')')
424			syntax("')' expected");
425			scan();
426			curfunc = ep1;
427			} else
428			curfunc = NULL;
429			#endif
430
431			if (nextc != '=')
432			syntax("'=' expected");
433			scan();
434
435			ep2 = newnode();
436			ep2->type = '=';
437			addekid(ep2, ep1);
438			addekid(ep2, getE1());
439
440			#ifdef FUNCTION
441			if (ep1->type == SYM)
442			#endif
443			{
444			ep1 = newnode();
445			ep1->type = TICK;
446			ep1->v.tick = -1;
447			addekid(ep2, ep1);
448			ep1 = newnode();
449			ep1->type = NUM;
450			addekid(ep2, ep1);
451			}
452
453			return(ep2);
454			}
455
456
457			#ifdef OUTCHAN
458			EPNODE *
459			getchan() /* A -> $N = E1 */
460			{
461			register EPNODE ep1, ep2;
462
463			if (nextc != '$')
464			syntax("missing '$'");
465			scan();
466
467			ep1 = newnode();
468			ep1->type = CHAN;
469			ep1->v.chan = getinum();
470
471			if (nextc != '=')
472			syntax("'=' expected");
473			scan();
474
475			ep2 = newnode();
476			ep2->type = '=';
477			addekid(ep2, ep1);
478			addekid(ep2, getE1());
479
480			return(ep2);
481			}
482			#endif
483
484
485
486			/*
487			* The following routines are for internal use only:
488			*/
489
490
491			static double
492			dvalue(name, d) /* evaluate a variable */
493			char *name;
494			EPNODE *d;
495			{
496			register EPNODE ep1, ep2;
497
498			if (d == NULL \|\| d->v.kid->type != SYM) {
499			eputs(name);
500			eputs(": undefined variable\n");
501			quit(1);
502			}
503			ep1 = d->v.kid->sibling; /* get expression */
504			ep2 = ep1->sibling; /* check time */
505			if (ep2->v.tick < 0 \|\| ep2->v.tick < eclock) {
506			ep2->v.tick = eclock;
507			ep2 = ep2->sibling;
508			ep2->v.num = evalue(ep1); /* compute new value */
509			} else
510			ep2 = ep2->sibling; /* reuse old value */
511
512			return(ep2->v.num);
513			}
514
515
516			static int
517			hash(s) /* hash a string */
518			register char *s;
519			{
520			register int rval = 0;
521
522			while (*s)
523			rval += *s++;
524
525			return(rval % NHASH);
526			}