[Python-checkins] CVS: python/dist/src/Grammar Grammar,1.44,1.45

[Guido van Rossum]

Update of /cvsroot/python/python/dist/src/Grammar
In directory usw-pr-cvs1:/tmp/cvs-serv24320/Grammar

Modified Files:
	Grammar 
Log Message:
Very subtle syntax change: in a list comprehension, the testlist in
"for <var> in <testlist> may no longer be a single test followed by
a comma.  This solves SF bug #431886.  Note that if the testlist
contains more than one test, a trailing comma is still allowed, for
maximum backward compatibility; but this example is not:

    [(x, y) for x in range(10), for y in range(10)]
                              ^

The fix involved creating a new nonterminal 'testlist_safe' whose
definition doesn't allow the trailing comma if there's only one test:

    testlist_safe: test [(',' test)+ [',']]



Index: Grammar
===================================================================
RCS file: /cvsroot/python/python/dist/src/Grammar/Grammar,v
retrieving revision 1.44
retrieving revision 1.45
diff -C2 -d -r1.44 -r1.45
*** Grammar	2001/08/08 05:00:17	1.44
--- Grammar	2001/10/15 15:44:04	1.45
***************
*** 90,93 ****
--- 90,94 ----
  exprlist: expr (',' expr)* [',']
  testlist: test (',' test)* [',']
+ testlist_safe: test [(',' test)+ [',']]
  dictmaker: test ':' test (',' test ':' test)* [',']
  
***************
*** 98,101 ****
  
  list_iter: list_for | list_if
! list_for: 'for' exprlist 'in' testlist [list_iter]
  list_if: 'if' test [list_iter]
--- 99,102 ----
  
  list_iter: list_for | list_if
! list_for: 'for' exprlist 'in' testlist_safe [list_iter]
  list_if: 'if' test [list_iter]