Re: [Haskell-cafe] Maybe a, The Rationale

On 11 May 2008, at 00:36, PR Stanley wrote:

Hi folks

data Maybe a = Nothing | Just a

What is the underlying rationale for the Maybe data type? is it the safe style of programming it encourages/ Something tells me this is going to start a lengthy discussion. :-)

Pure and simple -- it allows you to represent partial functions. Looking up a map will only sometimes find a value, so we either return Nothing, or Just that value. Bob