#include "expr.h"
#include <stdlib.h>

static GE_EXPRESSION **expr_list;
static uint32_t expr_cap = 0;
static uint32_t expr_count = 0;
static GE_EXPRESSION expr0 = {""};

GE_EXPRESSION *GE_new_expression() {
  GE_EXPRESSION *expr;
  if (expr_count==expr_cap) {
    uint32_t n = expr_count ? 2*expr_count : 100;
    expr_list = (GE_EXPRESSION**)realloc(expr_list, n*sizeof(GE_EXPRESSION *));
    expr_cap = n;
    for (; n-->expr_count;) 
      expr_list[n] = (GE_EXPRESSION*)malloc(sizeof(GE_EXPRESSION));
  }
  expr = expr_list[expr_count];
  ++expr_count;
  *expr = expr0;
  return expr;
}

void GE_push_back(GE_EXPRESSION **expr) {
  GE_EXPRESSION *ex = *expr;
  if (ex) {
    GE_push_back(&ex->details);
    GE_push_back(&ex->arg);
    GE_push_back(&ex->next);
    GE_push_back(&ex->down);
    --expr_count;
    expr_list[expr_count] = ex;
    *expr = NULL;
  }
}

GE_EXPRESSION *expr_bottom(GE_EXPRESSION* expr) {
  GE_EXPRESSION *ex = 0;
  for (; expr; expr=expr->down)  ex = expr;
  return ex;
}

GE_EXPRESSION *expr_last(GE_EXPRESSION* expr) {
  GE_EXPRESSION *ex = 0;
  for (; expr; expr=expr->next)  ex = expr;
  return ex;
}