[Haskell-cafe] Syntax proposal for "reverse apply"/"pipeline apply" (flip ($))

Malcolm Wallace malcolm.wallace at me.com
Fri Apr 18 10:09:20 UTC 2014

On 17 Apr 2014, at 20:20, Edward Kmett wrote:

> After the last time this made the rounds, this went to the core libraries committee.
> Consensus was achieved to add it as an infixl 1 & operator to Data.Function, but not to Prelude,so we just need to put in the patch and you'll see it in GHC 7.10.

I would like to strongly oppose the theft of the (&) operator from general use.  The proposal to put it in Data.Function, such that you need to know you are importing it, is OK, but it should never go into the Prelude.

My general position is that there are very few single-character operator names left for ordinary programmers to use locally in their code.  Given we now have more than twenty years usage of Haskell, I think it is pretty likely that people have made use of the flexibility to define their own operators for code that will never be widely shared.  Taking away those operators from users, to become "standard", will only break old code.

As a single datapoint, I grepped for uses of the & operator in our codebase at work, and found ~28,000 LoC where it is used.


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