[Python-checkins] python/nondist/peps pep-0336.txt, NONE, 1.1 pep-0000.txt, 1.293, 1.294

Wed Nov 3 17:58:32 CET 2004

Update of /cvsroot/python/python/nondist/peps
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv20583
Modified Files:
	pep-0000.txt 
Added Files:
	pep-0336.txt 
Log Message:
added PEP 336, "Make None Callable", by Andrew McClelland

--- NEW FILE: pep-0336.txt ---
PEP: 336
Title: Make None Callable
Version: $Revision: 1.1 $
Last-Modified: $Date: 2004年11月03日 16:58:30 $ 
Author: Andrew McClelland
Status: Draft
Type: Standards Track
Content-Type: text/plain 
Created: 28-Oct-2004
Post-History: 
Abstract
 None should be a callable object that when called with any
 arguments has no side effect and returns None.
Motivation
 To allow a programming style for selectable actions that is more
 in accordance with the minimalistic functional programming goals
 of the Python language.
Rationale
 Allow the use of None in method tables as a universal no effect
 rather than either (1) checking a method table entry against None
 before calling, or (2) writing a local no effect method with
 arguments similar to other functions in the table.
 The semantics would be effectively,
 class None:
 def __call__(self, *args):
 pass
How To Use
 Before, checking function table entry against None:
 class Select:
 def a(self, input):
 print 'a'
 def b(self, input):
 print 'b'
 def c(self, input);
 print 'c'
 def __call__(self, input):
 function = { 1 : self.a,
 2 : self.b,
 3 : self.c
 }.get(input, None)
 if function: return function(input)
 Before, using a local no effect method:
 class Select:
 def a(self, input):
 print 'a'
 def b(self, input):
 print 'b'
 def c(self, input);
 print 'c'
 def nop(self, input):
 pass
 def __call__(self, input):
 return { 1 : self.a,
 2 : self.b,
 3 : self.c
 }.get(input, self.nop)(input)
 After:
 class Select:
 def a(self, input):
 print 'a'
 def b(self, input):
 print 'b'
 def c(self, input);
 print 'c'
 def __call__(self, input):
 return { 1 : self.a,
 2 : self.b,
 3 : self.c
 }.get(input, None)(input)
References
 [1] Python Reference Manual, Section 3.2,
 http://docs.python.org/ref/ref.html
Copyright
 This document has been placed in the public domain.

Local Variables:
mode: indented-text
indent-tabs-mode: nil
sentence-end-double-space: t
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End:
Index: pep-0000.txt
===================================================================
RCS file: /cvsroot/python/python/nondist/peps/pep-0000.txt,v
retrieving revision 1.293
retrieving revision 1.294
diff -u -d -r1.293 -r1.294
--- pep-0000.txt	27 Oct 2004 10:09:55 -0000	1.293
+++ pep-0000.txt	3 Nov 2004 16:58:30 -0000	1.294
@@ -123,6 +123,7 @@
 S 332 Byte vectors and String/Unicode Unification Montanaro
 S 334 Simple Coroutines via SuspendIteration Evans
 S 335 Overloadable Boolean Operators Ewing
+ S 336 Make None Callable McClelland
 S 754 IEEE 754 Floating Point Special Values Warnes
 
 Finished PEPs (done, implemented in CVS)
@@ -366,6 +367,7 @@
 I 333 Python Web Server Gateway Interface v1.0 Eby
 S 334 Simple Coroutines via SuspendIteration Evans
 S 335 Overloadable Boolean Operators Ewing
+ S 336 Make None Callable McClelland
 SR 666 Reject Foolish Indentation Creighton
 S 754 IEEE 754 Floating Point Special Values Warnes
 I 3000 Python 3.0 Plans Kuchling, Cannon
@@ -431,6 +433,7 @@
 Lielens, Gregory gregory.lielens at fft.be
 von Loewis, Martin loewis at informatik.hu-berlin.de
 Martelli, Alex aleax at aleax.it
+ McClelland, Andrew eternalsquire at comcast.net
 McMillan, Gordon gmcm at hypernet.com
 McNamara, Andrew andrewm at object-craft.com.au
 Mick, Trent trentm at activestate.com
