[Haskell-cafe] Maybe a, The Rationale
Brandon S. Allbery KF8NH
allbery at ece.cmu.edu
Sat May 10 19:04:11 EDT 2008
On 2008 May 10, at 18:56, PR Stanley wrote:
>>> Paul: 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. :-)
>> Bob: Pure and simple -- it allows you to represent partial
>> Looking up a map will only sometimes find a value, so we either
>> Nothing, or Just that value.
> Paul: Would yu like to demonstrate this in an example?
Um, I was encountering and recognizing times when I really needed an
out-of-band "null", and the pain of representing such in C, shortly
after I started serious programming in C (call it 1984-5). Is this
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery at kf8nh.com
system administrator [openafs,heimdal,too many hats] allbery at ece.cmu.edu
electrical and computer engineering, carnegie mellon university KF8NH
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