On 26 Apr 2011, at 13:31, Eric Stansifer wrote:
Let 'c2h' convert CStrings to Haskell Strings, and 'h2c' convert Haskell Strings to CStrings. (If I understand correctly, c2h . h2c === id, but h2c . c2h is not the identity on all inputs;
That is correct. CStrings are 8-bits, and Haskell Strings are 32-bits. Converting from Haskell to C loses information, unless you use a multi-byte encoding on the C side (for instance, UTF8).
So actually I am incorrect, and h2c . c2h is the identity but c2h . h2c is not?
Ah, my bad. In reading the composition from right to left, I inadvertently read h2c and c2h from right to left as well! So, starting from C, converting to Haskell, and back to C is the identity, yes. Starting from Haskell, no. Regards, Malcolm