[Haskell-beginners] Offside rule for function arguments?

[Isaac Dupree]

On 08/23/10 15:02, Brandon S Allbery KF8NH wrote:
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> On 8/23/10 14:56 , Isaac Dupree wrote:
>> On 08/23/10 02:33, John Smith wrote:
>>> Why doesn't Haskell allow something like this?
>>>
>>> fac 0 = 0
>>>     1 = 1
>>>     x = x * fac (x-1)
>>>
>>> This would be clearer than repeating the function name each time, and
>>> follow the same pattern as guards and case.
>>
>> Layout is detected and parsed when and only when it is preceded by 'where',
>> 'let', 'do', or 'of'.  So Haskell would have to have some such keyword to
>
> I think the next question is "so how do guards work?"

Weirdly!  It's a bit like "|" is a prefix operator, at least when found 
in this relevant parsing-context (and not e.g. in a list comprehension). 
  The guards don't need to line up either.  I admit that I wasn't too 
happy when I found out how guards parse.  "|" looks way too symmetric of 
a character for it to do that... Linebreaks are not required! :

fac x | x==0 = 0 | x==1 = 1 | otherwise = x * fac (x-1)