#include "defs.h"
#include "prims.h"

PRIM(for_add)
{
 struct inst *vstart;
 struct inst *vstep;
 struct inst *vend;
 struct for_struct *loop;

 NARGS(3);
 vstep = TOS(0);
 vend = TOS(1);
 vstart = TOS(2);
 if (vstep->type != PROG_INTEGER) ABORT_INTERP("Invalid step size.");
 if (vend->type != PROG_INTEGER) ABORT_INTERP("Invalid end (for).");
 if (vstart->type != PROG_INTEGER) ABORT_INTERP("Invalid start (for).");
 loop = malloc(sizeof(*loop));
 loop->next = fr->for_loop;
 loop->current = vstart->data.number;
 loop->target = vend->data.number;
 loop->stepsize = vstep->data.number;
 fr->for_loop = loop;
 POP(3);
 MPUSH(PROG_INTEGER,loop->current);
}

PRIM(for_check)
{
 struct for_struct *loop;
 int cond;

 loop = fr->for_loop;
 if (! loop) ABORT_INTERP("Invalid check of FOR loop.");
 loop->current += loop->stepsize;
 if (loop->stepsize == 0) cond = 1;
 else if (loop->stepsize > 0) cond = (loop->current <= loop->target);
 else cond = (loop->current >= loop->target);
 if (! cond)
  { fr->for_loop = loop->next;
    free(loop);
  }
 else
  { STACKROOM(1);
    MPUSH(PROG_INTEGER,loop->current);
  }
 STACKROOM(1);
 MPUSH(PROG_INTEGER,cond);
}

PRIM(for_pop)
{
 struct inst *v;
 struct for_struct *loop;
 int i;

 NARGS(1);
 v = TOS(0);
 if (v->type != PROG_INTEGER) ABORT_INTERP("Internal FOR error: Invalid argument to for_pop.");
 for (i=v->data.number;i>0;i--)
  { loop = fr->for_loop;
    if (! loop) ABORT_INTERP("Internal FOR error: FOR stack underflow.");
    fr->for_loop = loop->next;
    free(loop);
  }
 POP(1);
}