toLower package:sbv

Convert to lower-case. Only works for the Latin1 subset, otherwise returns its argument unchanged.

>>> prove $ \c -> toLowerL1 (toLowerL1 c) .== toLowerL1 c
Q.E.D.

>>> prove $ \c -> isLowerL1 c .&& c `notElem` "\181\255" .=> toLowerL1 (toUpperL1 c) .== c
Q.E.D.