[Patches] [ python-Patches-1412451 ] Fill out the functional module

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Patches item #1412451, was opened at 2006-01-22 21:21
Message generated for change (Comment added) made by rhettinger
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Category: Modules
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Submitted By: Collin Winter (collinwinter)
Assigned to: Nobody/Anonymous (nobody)
Summary: Fill out the functional module

Initial Comment:
This patch is an expansion of my earlier patch,
#1410119, and should be considered to supersede it.

This patch fixes a reference leak in the earlier
implementation of foldr. The reference leak was tricky
to trigger, but existed.

In addition, this patch breaks the functional module
into two parts: Modules/_functionalmodule.c and
Lib/functional.py. The latter is for list-producing
functions which are better implemented as generators
(to make them lazier), while the former is reserved for
non-list-producing functions, written in C for speed.
Lib/functional.py imports the `_functional` module
generated from Modules/_functionalmodule.c.

The total contents of the functional module:
+ compose
+ concat
+ concatMap
+ cycle
+ drop
+ dropWhile
+ flip
+ foldl
+ foldl1
+ foldr
+ foldr1
+ id
+ iterate
+ partial
+ repeat
+ scanl
+ scanl1
+ scanr
+ scanr1
+ take
+ takeWhile

In addition to a full test-suite and latex-formatted
documentation for all functions, this patch also adds a
functional/ directory to Demo/ and populates it with
examples.

After applying this patch, the existing
Modules/functionalmodule.c should be removed and
replaced with the attached _functionalmodule.c (sorry,
I couldn't figure out how to make this show up in an
svn diff reliably).

The patch is against svn revision 42148.

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>Comment By: Raymond Hettinger (rhettinger)
Date: 2006-02-01 14:59

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I am strongly against the broad expansion of this module 
until it has lived for some time as a successful, mature, 
well-loved stand-alone module.

Each addition needs to be fully thought-out in terms of 
use cases and evaluated for clarity/efficacy against 
existing Python solutions.

At some point, there was a substantial discussion on just 
the compose() function.  While it seems basic to 
functional programming, it was found not to be necessary, 
and not represent much of an improvement over a simple 
lambda expression.  Also, a number of folks have 
difficulty remembering whether compose(f,g) means f(g(x)) 
or g(f(x)).

Also, some of these entries duplicate those in the 
itertools module.  It is not in Python's best interests to 
provide several ways of doing the same thing.


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Comment By: Brett Cannon (bcannon)
Date: 2006-02-01 14:15

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Do note that the function names do not follow the naming
convention specified in PEP 8.

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Comment By: Collin Winter (collinwinter)
Date: 2006-02-01 05:27

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I've updated functional.patch to remove functions that are
already handled in itertools. The remaining functions which
had been implemented in Python have now all been recoded in
C. All functions have seen implementation improvements since
the last version of the patch.

This patch removes the need for the icky "manually add
_functionalmodule.c" part of the original patching
instructions. No special actions are necessary now.

The patch is against svn revision 42219.

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Comment By: Collin Winter (collinwinter)
Date: 2006-01-23 07:55

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I've broken the main functional.patch into two subpatches.
demo.patch creates and populates the Demo/functional/
directory, while functional.patch does all the rest.

Both patches are updated to r42155.

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