[Python-checkins] CVS: python/nondist/peps pep-0237.txt,1.10,1.11

[Guido van Rossum]

Update of /cvsroot/python/python/nondist/peps
In directory usw-pr-cvs1:/tmp/cvs-serv26695

Modified Files:
	pep-0237.txt 
Log Message:
Explain the semantics of OverflowWarning, for the benefit of the
documenter.  Clarify a few other issues (some brought up by Martin von
Loewis in private email).


Index: pep-0237.txt
===================================================================
RCS file: /cvsroot/python/python/nondist/peps/pep-0237.txt,v
retrieving revision 1.10
retrieving revision 1.11
diff -C2 -d -r1.10 -r1.11
*** pep-0237.txt	2001/08/14 19:30:15	1.10
--- pep-0237.txt	2001/08/23 03:50:54	1.11
***************
*** 122,125 ****
--- 122,143 ----
        optimization.
  
+     - The expression type(x).__name__ depends on whether x is a short
+       or a long int.  Since implementation alternative 2 is chosen,
+       this difference will remain.
+ 
+     - Long and short ints are handled different by the marshal module,
+       and by the pickle and cPickle modules.  This difference will
+       remain.
+ 
+     - Short ints with small values (typically between -1 and 99
+       inclusive) are "interned" -- whenever a result has such a value,
+       an existing short int with the same value is returned.  This is
+       not done for long ints with the same values.  This difference
+       will remain.  (Since there is no guarantee of this interning, is
+       is debatable whether this is a semantic difference -- but code
+       may exist that uses 'is' for comparisons of short ints and
+       happens to work because of this interning.  Such code may fail
+       if used with long ints.)
+ 
  
  Literals
***************
*** 164,169 ****
         depends on this exception would have to be too convoluted to be
         concerned about it.)  For those concerned about extreme
!        backwards compatibility, a command line option will allow a
!        warning to be issued at this point, but this is off by default.
  
      B. The remaining semantic differences are addressed.  In most
--- 182,188 ----
         depends on this exception would have to be too convoluted to be
         concerned about it.)  For those concerned about extreme
!        backwards compatibility, a command line option (or a call to
!        the warnings module) will allow a warning or an error to be
!        issued at this point, but this is off by default.
  
      B. The remaining semantic differences are addressed.  In most
***************
*** 206,209 ****
--- 225,276 ----
  
  
+ OverflowWarning
+ 
+     Here are the rules that guide warnings generated in situations
+     that currently raise OverflowError.  This applies to transition
+     phase A.
+ 
+     - A new warning category is introduced, OverflowWarning.  This is
+       a built-in name.
+ 
+     - If an int result overflows, an OverflowWarning warning is
+       issued, with a message argument indicating the operation,
+       e.g. "integer addition".  This may or may not cause a warning
+       message to be displayed on sys.stderr, or may cause an exception
+       to be raised, all under control of the -W command line and the
+       warnings module.
+ 
+     - The OverflowWarning warning is ignored by default.
+ 
+     - The OverflowWarning warning can be controlled like all warnings,
+       via the -W command line option or via the
+       warnings.filterwarnings() call.  For example:
+ 
+         python -Wdefault::OverflowWarning
+ 
+       cause the OverflowWarning to be displayed the first time it
+       occurs at a particular source line, and
+ 
+         python -Werror::OverflowWarning
+ 
+       cause the OverflowWarning to be turned into an exception
+       whenever it happens.  The following code enables the warning
+       from inside the program:
+ 
+         import warnings
+         warnings.filterwarnings("default", "", OverflowWarning)
+ 
+       See the python man page for the -W option and the the warnings
+       module documentation for filterwarnings().
+ 
+     - If the OverflowWarning warning is turned into an error,
+       OverflowError is substituted.  This is needed for backwards
+       compatibility.
+ 
+     - Unless the warning is turned into an exceptions, the result of
+       the operation (e.g., x+y) is recomputed after converting the
+       arguments to long ints.
+ 
+ 
  Example
  
***************
*** 230,238 ****
  
  
! Open Issues
  
!     We expect that these issues will be resolved over time, as more
!     feedback is received or we gather more experience with the initial
!     implementation.
  
      - What to do about sys.maxint?  Leave it in, since it is still
--- 297,303 ----
  
  
! Resolved Issues
  
!     These issues, previously open, have been resolved.
  
      - What to do about sys.maxint?  Leave it in, since it is still