[Python-ideas] new operators via backquoting

[Brett Cannon]

On 1/2/07, Chris Rebert <cvrebert at gmail.com> wrote:
>
> In Haskell,  foo `baz` bar  means  (baz foo bar), which translates to
> baz(foo, bar) in Python. This allows Haskell programmers to use
> functions as infix operators.
> If I recall correctly, in Py3k, enclosing something in backticks will no
> longer cause it to be repr()-ed, leaving the backtick without a meaning
> in Python.


Right.  I removed that back in August at the Google sprint.

Thus, I propose one of the following as the new use for the backtick (`):
> [Note: In both, the characters between the backticks must be a valid
> Python identifier.]
>
> (A)  `baz` is treated as an operator, named "baz", just as / is "div".
> foo `baz` bar  thus causes python to try to call  foo.__baz__(bar), and
> failing that, bar.__rbaz__(foo), and if both those fail, raise
> TypeError. This is, if I understand correctly, how the builtin operators
> work.



(B)  `baz` is a special way to call a callable. foo `baz` bar  is
> translated to  baz(foo, bar)  with the standard lookup rules for
> resolving "baz"
>
>
> Example use cases, stolen from Haskell: The Craft of Functional
> Programming:
> 2 `max` 5  =>  5
> 7 `cons` tail  =>  ConsCell(val=7, next=tail)
> matrix1 `crossproduct` matrix2  =>  cross-product of the matrices
> [1, 2, 3] `zip` ['a', 'b', 'c']  =>  [[1, 'a'], [2, 'c'], [3, 'c']]
>
> I believe that this would improve the readability of code, such as
> Numeric, without going off the deep end and offering programmable syntax.



Big -1 from me.  I hate this feature from Haskell.  It is a step towards
programmable syntax and I think that's just a messy.  And having it become a
magic method that is called instead of just some function that takes two
arguments really sends us down that road.

-Brett
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