function tuple(var bool, var int): element_safe(
	array of int: a,
	var int: x
) =
	let {
		set of int: idx = index_set(x)
		var bool: total = x in idx;
		var idx: xs;
		int: m = min(idx);
		% Give xs the value of x when result is total
		constraint total -> xs = x; 
		% Otherwise, give xs the value m instead to avoid a free variable
		constraint not total -> xs = m;
		% element constraint that is guaranteed to be total
		tuple(var bool, var int): ret = (total, element(a, xs));
	} in ret;