Plan 9 from Bell Labs’s /usr/web/sources/contrib/fernan/nhc98/src/prelude/Ix/Ix_Integer.hs
module Ix(Ix(..)) where import CIx instance Ix Integer where range (m,n) = [m .. n] index b@(m,n) i | inRange b i = fromInteger (i - m) | True = error "Ix.Integer.index: Index out of range." inRange (m,n) i = m <= i && i <= n