[Python-ideas] Infix functions

[Andrew Barnert]

From: Mathias Panzenböck <grosser.meister.morti at gmx.net>
Sent: Friday, February 21, 2014 5:45 PM


>Am 2014-02-21 23:05, schrieb Andrew Barnert:
>> While we're discussing crazy ideas inspired by a combination of a long-abandoned PEP and Haskell idioms (see the implicit lambda thread), here's another: arbitrary infix operators:
>>
>>      a `foo` b == foo(a, b)
>>
>
>If you really want to you could do this:


This is basically the same trick you use in Haskell to allow arbitrary expressions rather than just identifiers to be used infix. Which I don't think you actually want to allow. Also, it requires you to declare certain functions as infix-able rather than just use any functions arbitrarily. Of course that does allow you to give the infix version a different name than the prefix version, like bar = infix(foo), or even bar = infix(partial(Spam(2).long_method_name, 'eggs')), which could I suppose be useful.

One question about the implementation:

>    class infix2(object):
>        __slots__ = 'func', 'arg1'
>    
>        def __init__(self,func,arg1):
>            self.func = func
>            self.arg1 = arg1
>    
>        def __call__(*args,**kwargs):
>            self, args = args[0], args[1:]
>            return self.func(self.arg1,*args,**kwargs)


First, why not just:

    def __call__(self, *args, **kwargs):
        return self.func(self.arg1, *args, **kwargs)

More importantly, I assume this is to allow auto-partialing, so "spam" |foo is a normal function of one argument that you can pass around? That doesn't actually work the same way as Haskell operators, and it looks pretty weird in Python too, and I can't think of when you'd want it, but it is clever.