String.hs

  -- | This module contains some common String funcions
module Database.Design.Ampersand.Basics.String (unCap,upCap,escapeNonAlphaNum) where

import Data.Char

-- | Converts the first character of a string to lowercase, with the exception that there is a second character, which is uppercase.
-- uncap "AbcDe" == "abcDe"
-- uncap "ABcDE" == "ABcDE"
unCap :: String -> String
unCap [] = []
unCap [h] = [toLower h]
unCap (h:h':t) | isUpper h' = h:h':t
               | otherwise  = toLower h:h':t
-- | Converts the first character of a string to uppercase
upCap :: String -> String
upCap [] = []
upCap (h:t) = toUpper h:t

-- | escape anything except regular characters and digits to _<character code>
-- e.g. escapeNonAlphaNum "a_é" = "a_95_233"
escapeNonAlphaNum :: String -> String
escapeNonAlphaNum = concatMap escapeNonAlphaNumChar
 where escapeNonAlphaNumChar c
         | isAlphaNum c && isAscii c = [c]
         | otherwise                 = '_' : show (ord c)