[Haskell-cafe] Why is $ right associative instead of left associative?

Brian Hulley brianh at metamilk.com
Sat Feb 4 09:52:20 EST 2006

Hi -
In the Haskell98 report section 4.4.2 $ is specified as being right 
associative. This means that f $ a0 a1 $ b0 b1 would parse as f (a0 a1 (b0 
b1)) which seems rather strange to me. Surely it would be much more useful 
if $ were defined as left associative so that it could be used to separate 
the args to f?

Does anyone know why this strange associativity was chosen?

Thanks, Brian.

(The reason I'm asking is that I'm working on the syntax of a language 
similar to Haskell but which uses layout to allow expressions like:

                 f #$                     -- can be followed by an explicit 
block or layout block
                        a0 a1
                        b0 b1

which is sugar for (f $ a0 a1) $ b0 b1 ie f (a0 a1) (b0 b1) ) and I was 
surprised to discover that the parentheses are needed for the most obvious 

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