How do I dynamically create functions without lambda?

[Kay Schluehr]

Steven D'Aprano wrote:
> On Sat, 28 Jan 2006 00:13:28 -0800, Kay Schluehr wrote:
>
> [snip lambda calculus stuff]
>
> > In Python you can write:
> >
> > Y = lambda g: (lambda f: g(lambda arg: f(f)(arg))) (lambda f: g(lambda
> > arg: f(f)(arg)))
> >
> > This serves the purpose. Try Y(F) and see.
>
>
> Is any of this stuff maintainable in the real world of IT, where
> most programmers don't have computer science degrees?

Probably not. But the good thing about Y is that it is in closed form
and the expression is not infinitely long. By the way I have no less a
hard time to read C code with advanced data-structures and many type
casts which is much more likely to happen in the "real world".

>From what I've seen the only *practical* purpose fixpoint combinators
serve is a kind of recursion "overloading". Without modifying F one can
memoize values by adapting the fixpoint combinator. We already know
something similar from the Go4 "command pattern" but there is no
self-referential entanglement and it is less general.

> You come along six
> months after the project was finished to maintain this code and discover
> that the whiz-kid lambda calculus guy never commented anything because
> that would detract from the elegance of his one liners; what happens next?

Ask a Scheme guy at LtU. Accuse the original author in Den Haag and if
caught put him to shame by making photos at a dentist. Google for
"lambda calculus Y". Ask someone here at comp.lang.python. Ask your
boss for more time ;)

Kay