function.c

#include "function.h"
#include "ast.h"
#include "symbol_table.h"
#include "Loops.h"
#include <stdlib.h>

struct ast *newuserfunction(struct symbol *s, struct ast *l) {
  struct userfunction *a = malloc(sizeof(struct userfunction));
  if (!a) {
    yyerror("out of space");
    exit(0);
  }
  a->nodetype = 'C';
  a->l = l;
  a->s = s;
  return (struct ast *)a;
}

double calluserfunction(struct userfunction *f) {
  struct symbol *fn = f->s; /* function name */
  struct symlist *sl;       /* dummy arguments */
  struct ast *args = f->l;  /* actual arguments */
  double *oldval, *newval;  /* saved arg values */
  double v;
  int nargs;
  int i;
  if (!fn->func) {
    yyerror("call to undefined function", fn->name);
    return 0;
  }
  /* count the arguments */
  sl = fn->syms;
  for (nargs = 0; sl; sl = sl->next)
    nargs++;
  /* prepare to save them */
  oldval = (double *)malloc(nargs * sizeof(double));
  newval = (double *)malloc(nargs * sizeof(double));
  if (!oldval || !newval) {
    yyerror("Out of space in %s", fn->name);
    return 0.0;
  }
  /* evaluate the arguments */
  for (i = 0; i < nargs; i++) {
    if (!args) {
      yyerror("too few args in call to %s", fn->name);
      free(oldval);
      free(newval);
      return 0.0;
    }
    if (args->nodetype == 'L') { /* if this is a list node */
      newval[i] = eval(args->l);
      args = args->r;
    } else { /* if it's the end of the list */
      newval[i] = eval(args);
      args = NULL;
    }
  }
  /* save old values of dummies, assign new ones */
  sl = fn->syms;
  for (i = 0; i < nargs; i++) {
    struct symbol *s = sl->sym;
    oldval[i] = s->value;
    s->value = newval[i];
    sl = sl->next;
  }
  free(newval);
  /* evaluate the function */
  v = eval(fn->func);
  /* put the real values of the dummies back */
  sl = fn->syms;
  for (i = 0; i < nargs; i++) {
    struct symbol *s = sl->sym;
    s->value = oldval[i];
    sl = sl->next;
  }
  free(oldval);
  return v;
}