New PEP: Reduce-Map Comprehensions (and the "last" builtin)

[petered]

This PEP proposes the addition of new "Reduce-Map" comprehension. The Reduce-Map comprehension would perform a reduction while keeping intermediate elements. We also propose a built-in function "last", which, combined with a Reduce-Map comprehension, would allow us to replace the reduce builtin with a call to get the last element of a Reduce-Map generator.

Example:

smooth_signal = [average = (1-decay)*average + decay*x for x in signal from average=0.]

[the-knights-who-say-ni]

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[zware]

Hi @petered, and thanks for your interest in improving Python. However, your proposal has some procedural issues and your draft document does not conform to the standard PEP format. See PEP 12 for a guide to PEP formatting.

First, though, you should raise this idea on the python-ideas@python.org mailing list. The folks there will give you valuable feedback, which can either be incorporated into your PEP or possibly convince you that your PEP isn't necessary.

You will also need to sign the CLA; see the message from @the-knights-who-say-ni above for details on that.

For now, I'm going to close this PR. After you've discussed the idea on python-ideas and the formatting is fixed, please feel free to open a new PR.