| > Similarly, the greatest finite double value can be written as | > 0x1.fffffffffffffp+1023. | > | > These constants have the form | > | > 0x[HH][.HHHHH]p[+/-]DDD | | If you don't want to wait on an (uncertain) inclusion into the Haskell | standard, you can implement a small helper function to that effect | yourself; essentially using encodeFloat . Or, alternatively, use quasiquoting [hex| 1.fffffp+1023 |] where 'hex' is a Haskell function that parses the string. http://www.haskell.org/ghc/docs/latest/html/users_guide/template-haskell.htm... This has the advantage that you can use the constant in patterns too. (In GHC 6.12 you have to say [$hex| 1.ffffp+1023 |], with a "$", but we're changing that for 6.14. There's a thread on ghc-users about it.) Simon