Replaced usage of n+k pattern by conditions.
Defined A as A : Set. Otherwise did not typecheck.
Added {-# BUILTIN IO IO #-}
Removed id import. Changed return type from Set to Set1 for -_->_is_

Removed id import because it is not in the module.
Changed return type from Set to Set1 for -_->_is_ because S -> T has
type Set1.