/**
 * Memoize (by reference on the input parameter) the given arity 1 function.
 * 
 * * also works with primitive keys
 * * keys will *never* be garbage collected (even if they're not
 * primitive); this may or may not be ok, depending on the use case
 * * will also work with `object`s but since this will hold a reference and
 * prevent garbage collection, rather use `memoize` instead
 */
function memoizePrimitive<T, U>(f: (a: T) => U): (a: T) => U {
	const results = new Map<T,U>();
	
	return function(a: T): U {
		let result = results.get(a);
		if (result !== undefined) {
			//console.log('cache hit');
			return result; 
		}

		//console.log('cache miss');
		result = f(a);
		results.set(a, result);
		
		return result;
	}
}