Nick Coghlan <[email protected]> added the comment:
For flip, const and identity I agree there are already better ways to handle
them using either itertools or comprehension syntax.
The problem I have with trampoline is that it depends on the function's *return
values* being defined in a certain way (i.e. returning a zero-argument callable
instead of just calling them).
The other major factor limiting the appeal of some of the more complex
functional programming tools (the one that almost lead to lambda's removal in
3.x) is the availability of nested function definitions.
To rephrase Raymond's last example in more idiomatic Python:
def fg2(x):
# Comment or docstring explaining fg2
return f(g(2,x)
def h2(x, y):
# Comment or docstring explaining h2
return h(x, 3, y, flag=True)
result = [fg2(x), h2(x, y) for x, y in zip(X, Y) if x>y//2]
I see compose as being the most potential useful, as it would allow us to
provide a C accelerated version of the following alternative to trampoline:
def compose(*args):
def _composed(x):
for f in args:
x = f(x)
return x
return _composed
While this actually does match the mathematical definition, I agree pointing
that out is more confusing than helpful for many people (since the "inside-out"
nested evaluation ends up looking like "right-to-left" evaluation when written
down)
Raymond's proposed alternative to trampoline could then be written:
compose(*get_actions())(x)
----------
nosy: +ncoghlan
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