[Haskell-cafe] Desugaring of infix operators is (always?) the wrong way round

Sam Hughes hughes at rpi.edu
Tue Sep 25 20:46:56 EDT 2007

Brian Hulley wrote:
> Dan Piponi wrote:
>> On 9/25/07, Brian Hulley <brianh at metamilk.com> wrote:
>>> ..

> I don't understand what you mean. For example, with the prefix 
> definition of a function with multiple clauses, the function name at the 
> start of each clause is already lined up since it must appear at the 
> margin of the current layout block (especially if you follow the simple 
> rule of always following a layout starter token by a newline rather than 
> starting a new multi-line layout block in the middle of a line), whereas 
> with the postfix notation you'd need to manually line up the function 
> names if you wanted the same neat look.

Or you could have everything be backwards, and use an editor that right 
aligns things.

>>> It's not so clear to me what the syntax for types should be in a 
>>> postfix language.
>> Postfix, of course! So you'd write
>> data a Tree = Leaf | a a Tree

                                 a a Tree |
                                     Leaf = a Tree

> A postfix version could be:
>    map :: (a -> b) -> a List -> b List
>    Empty _ map = Empty
>    (h t PushF) f map = (h f) (t f map) PushF

            (a -> b) -> [a] -> [b] ::          map
                                 [] = []     _ map
                     x f : xs f map = (x:xs) f map

- Sam

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