Simple haskell string manage

subs :: String -> String -> String -> String
-- example:
-- subs 'x' "x^3 + x + sin(x)" "6.2" will generate
--          "6.2^3 + 6.2 + sin(6.2)"

import Text.Regex(mkRegex, subRegex)

subs :: String -> String -> String -> String
subs wildcard input value = subRegex (mkRegex wildcard) input value

import Text.Format
format "{0}^3 + {0} + sin({0})" ["6.2"]