public List <Tuple <int, int> > Call <Name>(Named <List <int>, Name> named)
{
var len1 = Zipper.Len(this.xs);
var len2 = Zipper.Len(named);
var proof1 = Zipper.LengthIsTwo(len1);
var proof2 = Zipper.LengthIsTwo(len2);
if (proof1 != null && proof2 != null)
{
return(Zipper.Zip(
new SuchThat <Named <List <int>, Xs>, Equals <Length <Xs>, Succ <Succ <Zero> > > >(this.xs, proof1),
new SuchThat <Named <List <int>, Name>, Equals <Length <Name>, Succ <Succ <Zero> > > >(named, proof2)));
}
throw new Exception("Lists were not of length 2.");
}
