[Python-checkins] CVS: python/nondist/peps pep-0239.txt,1.5,1.6

2001年8月08日 08:36:43 -0700

Update of /cvsroot/python/python/nondist/peps
In directory usw-pr-cvs1:/tmp/cvs-serv8456
Modified Files:
	pep-0239.txt 
Log Message:
Add nice summary by Marcin 'Qrczak' Kowalczyk from c.l.py for and
against unifying ints and rats.
Index: pep-0239.txt
===================================================================
RCS file: /cvsroot/python/python/nondist/peps/pep-0239.txt,v
retrieving revision 1.5
retrieving revision 1.6
diff -C2 -d -r1.5 -r1.6
*** pep-0239.txt	2001年07月29日 09:49:26	1.5
--- pep-0239.txt	2001年08月08日 15:36:41	1.6
***************
*** 72,75 ****
--- 72,106 ----
 For rational numbers with integer values?
 
+ - Marcin 'Qrczak' Kowalczyk summarized the arguments for and
+ against unifying ints with rationals nicely on c.l.py:
+ 
+ Arguments for unifying ints with rationals:
+ 
+ - Since 2 == 2/1 and maybe str(2/1) == '2', it reduces surprises
+ where objects seem equal but behave differently.
+ 
+ - / can be freely used for integer division when I *know* that
+ there is no remainder (if I am wrong and there is a remainder,
+ there will probably be some exception later).
+ 
+ Arguments against:
+ 
+ - When I use the result of / as a sequence index, it's usually
+ an error which should not be hidden by making the program
+ working for some data, since it will break for other data.
+ 
+ - (this assumes that after unification int and rational would be
+ different types:) Types should rarely depend on values. It's
+ easier to reason when the type of a variable is known: I know
+ how I can use it. I can determine that something is an int and
+ expect that other objects used in this place will be ints too.
+ 
+ - (this assumes the same type for them:) Int is a good type in
+ itself, not to be mixed with rationals. The fact that
+ something is an integer should be expressible as a statement
+ about its type. Many operations require ints and don't accept
+ rationals. It's natural to think about them as about different
+ types.
+ 
 
 References