23 Mar
2014
23 Mar
'14
2:30 p.m.
Am 23.03.2014 19:16, schrieb Tom Ellis:
On Sun, Mar 23, 2014 at 01:50:43AM -0700, Bart Massey wrote:
:m + Numeric.Lens Control.Lens "7b" ^? hex Just 123 hex # 123 "7b"
Nice. Once this really becomes standard, I guess we'll be somewhere.
Unless there's some way I'm unaware of to statically verify that the string indeed represents a valid hex encoding, then this is still not a complete solution.
Since the original complaint was about parsing, there must be a way to fail. The first line ("7b" ^? hex) seems to allow failure. For literal hex input we have 0x7b. However I don't see a problem with readHex. Prelude> case Numeric.readHex "7b" of [(n,"")] -> print n; _ -> putStrLn "could not parse hex number" 123