public static Query RandomMember <T>(this VarList <T> list, Var <T> member)
{
var listLength = new Var <int>();
var randomIndex = new Var <int>();
return(list.Length(listLength)
& Query.Random(listLength, randomIndex)
& list.Nth(randomIndex, member));
}
public static Query Nth <T>(this VarList <T> list, Var <int> index, Var <T> element)
{
var head = new Var <T>();
var tail = new VarList <T>();
return(list <= (head, tail)
& ((head <= element & index <= 0)
| (() =>
{
var innerIndex = new Var <int>();
return tail.Nth(innerIndex, element)
& index <= innerIndex.Inc;
})
));
}