grap/for.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include "grap.h"
   4 #include "y.tab.h"
   5
   6 typedef struct {
   7         Obj     *var;   /* index variable */
   8         double  to;     /* limit */
   9         double  by;
  10         int     op;     /* operator */
  11         char    *str;   /* string to push back */
  12 } For;
  13
  14 #define MAXFOR  10
  15
  16 For     forstk[MAXFOR]; /* stack of for loops */
  17 For     *forp = forstk; /* pointer to current top */
  18
  19 void forloop(Obj *var, double from, double to, int op, double by, char *str)    /* set up a for loop */
  20 {
  21         fprintf(tfd, "# for %s from %g to %g by %c %g \n",
  22                 var->name, from, to, op, by);
  23         if (++forp >= forstk+MAXFOR)
  24                 ERROR "for loop nested too deep" FATAL;
  25         forp->var = var;
  26         forp->to = to;
  27         forp->op = op;
  28         forp->by = by;
  29         forp->str = str;
  30         setvar(var, from);
  31         nextfor();
  32         unput('\n');
  33 }
  34
  35 void nextfor(void)      /* do one iteration of a for loop */
  36 {
  37         /* BUG:  this should depend on op and direction */
  38         if (forp->var->fval > SLOP * forp->to) {        /* loop is done */
  39                 free(forp->str);
  40                 if (--forp < forstk)
  41                         ERROR "forstk popped too far" FATAL;
  42         } else {                /* another iteration */
  43                 pushsrc(String, "\nEndfor\n");
  44                 pushsrc(String, forp->str);
  45         }
  46 }
  47
  48 void endfor(void)       /* end one iteration of for loop */
  49 {
  50         switch (forp->op) {
  51         case '+':
  52         case ' ':
  53                 forp->var->fval += forp->by;
  54                 break;
  55         case '-':
  56                 forp->var->fval -= forp->by;
  57                 break;
  58         case '*':
  59                 forp->var->fval *= forp->by;
  60                 break;
  61         case '/':
  62                 forp->var->fval /= forp->by;
  63                 break;
  64         }
  65         nextfor();
  66 }
  67
  68 char *ifstat(double expr, char *thenpart, char *elsepart)
  69 {
  70         dprintf("if %g then <%s> else <%s>\n", expr, thenpart, elsepart? elsepart : "");
  71         if (expr) {
  72                 unput('\n');
  73                 pushsrc(Free, thenpart);
  74                 pushsrc(String, thenpart);
  75                 unput('\n');
  76                 if (elsepart)
  77                         free(elsepart);
  78                 return thenpart;        /* to be freed later */
  79         } else {
  80                 free(thenpart);
  81                 if (elsepart) {
  82                         unput('\n');
  83                         pushsrc(Free, elsepart);
  84                         pushsrc(String, elsepart);
  85                         unput('\n');
  86                 }
  87                 return elsepart;
  88         }
  89 }