[Python-Dev] PEP 443 - Single-dispatch generic functions (original) (raw)

Devin Jeanpierre jeanpierreda at gmail.com
Thu May 23 08:33:57 CEST 2013

On Thu, May 23, 2013 at 2:04 AM, Antoine Pitrou <solipsis at pitrou.net> wrote:

On Thu, 23 May 2013 12:12:26 +1000 Nick Coghlan <ncoghlan at gmail.com> wrote:

The binary operators can be more accurately said to use a complicated single-dispatch dance rather than supporting native dual-dispatch. Not one based on the type of a single argument, though.

Why not?

I'd expect it to look something like this:

@singledispatch
def ladd(left, right):
    return NotImplemented

@singledispatch
def radd(right, left):
    return NotImplemented

def add(left, right):
    x = ladd(left, right)
    if x is not NotImplemented:
        return x
    x = radd(right, left)
    if x is not NotImplemented:
        return x
    raise TypeError

Then instead of defining add you define an overloaded implementation of ladd, and instead of defining radd you define an overloaded implementation of radd.

-- Devin

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