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
>> functions.
>> Looking up a map will only sometimes find a value, so we either
>> return
>> 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
really difficult?
--
brandon s. allbery [solaris,freebsd,perl,pugs,haskell]
allbery@...
system administrator [openafs,heimdal,too many hats]
allbery@...
electrical and computer engineering, carnegie mellon university KF8NH
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