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Parallel => Lockstep everywhere. 

Replaced the reference implementation with one that's closer to what
the C code will actually look like; i.e. it obeys the iteration
protocol.

Other grammar and spelling fixes.
This commit is contained in:
Barry Warsaw 2000-07-28 05:48:25 +00:00
parent ff898c8e8a
commit a4a4286ce1
1 changed files with 27 additions and 25 deletions
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52
pep-0201.txt
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@ -1,5 +1,5 @@
PEP: 201
Title: Parallel Iteration
Title: Lockstep Iteration
Version: $Revision$
Author: bwarsaw@beopen.com (Barry A. Warsaw)
Python-Version: 2.0
@ -10,14 +10,14 @@ Post-History: 27-Jul-2000
Introduction
This PEP describes the `parallel iteration' proposal for Python
2.0, previously known as `parallel for loops'. This PEP tracks
the status and ownership of this feature, slated for introduction
in Python 2.0. It contains a description of the feature and
outlines changes necessary to support the feature. This PEP
summarizes discussions held in mailing list forums, and provides
URLs for further information, where appropriate. The CVS revision
history of this file contains the definitive historical record.
This PEP describes the `lockstep iteration' proposal for Python
2.0. This PEP tracks the status and ownership of this feature,
slated for introduction in Python 2.0. It contains a description
of the feature and outlines changes necessary to support the
feature. This PEP summarizes discussions held in mailing list
forums, and provides URLs for further information, where
appropriate. The CVS revision history of this file contains the
definitive historical record.
Motivation
@ -33,9 +33,9 @@ Motivation
iterations by introducing a new builtin function called `zip'.
Parallel For-Loops
Lockstep For-Loops
Parallel for-loops are non-nested iterations over two or more
Lockstep for-loops are non-nested iterations over two or more
sequences, such that at each pass through the loop, one element
from each sequence is taken to compose the target. This behavior
can already be accomplished in Python through the use of the map()
@ -70,10 +70,10 @@ Parallel For-Loops
[(1, 4), (2, 5), (3, 6), (None, 7)]
For these reasons, several proposals were floated in the Python
2.0 beta time frame for providing a better spelling of parallel
2.0 beta time frame for providing a better spelling of lockstep
for-loops. The initial proposals centered around syntactic
changes to the for statement, but conflicts and problems with the
syntax were unresolvable, especially when parallel for-loops were
syntax were unresolvable, especially when lockstep for-loops were
combined with another proposed feature called `list
comprehensions' (see pep-0202.txt).
@ -140,21 +140,23 @@ Examples
Reference Implementation
Here is a reference implementation, in Python of the zip()
built-in function. These would ultimately be replaced by
equivalent C code.
built-in function. This will be replaced with a C implementation
after final approval.
def zip(*args):
if not args:
raise TypeError('zip() expects one or more sequence arguments')
ret = []
# find the length of the shortest sequence
shortest = min(*map(len, args))
for i in range(shortest):
item = []
for s in args:
item.append(s[i])
ret.append(tuple(item))
return ret
i = 0
try:
while 1:
item = []
for s in args:
item.append(s[i])
ret.append(tuple(item))
i = i + 1
except IndexError:
return ret
BDFL Pronouncements
@ -165,8 +167,8 @@ BDFL Pronouncements
- The function's name. An earlier version of this PEP included an
open issue listing 20+ proposed alternative names to zip(). In
the face of no overwhelmingly better choice, the BDFL strongly
prefers zip() due to it's Haskell[2] heritage. See version 1.7
of this PEP for the list of alteratives.
prefers zip() due to its Haskell[2] heritage. See version 1.7
of this PEP for the list of alternatives.
- zip() shall be a built-in function.