// ignore-test Not a test. Used by other tests

#![allow(dead_code)]  // Tests don't ordinarily use every feature and every accessor.

use std::rc::Rc;
use cell_gc::HeapSession;

#[derive(Clone, Debug, IntoHeap)]
pub struct Pair<'h> {
    pub head: Value<'h>,
    pub tail: Value<'h>
}

#[derive(Clone, Debug, PartialEq, IntoHeap)]
pub enum Value<'h> {
    Null,
    Int(i32),
    Str(Rc<String>),  // <-- equality is by value
    Pair(PairRef<'h>)  // <-- equality is by pointer
}

/// Helper function to avoid having to write out `Pair` literals all over the place.
pub fn alloc_pair<'h>(hs: &mut HeapSession<'h>, head: Value<'h>, tail: Value<'h>) -> PairRef<'h> {
    hs.alloc(Pair { head: head, tail: tail })
}

/// Allocate a pair with the values `(null, null)`.
pub fn alloc_null_pair<'h>(hs: &mut HeapSession<'h>) -> PairRef<'h> {
    alloc_pair(hs, Value::Null, Value::Null)
}