[Python-checkins] python/dist/src/Doc/ref ref5.tex,1.82,1.83

[rhettinger at users.sourceforge.net]

Update of /cvsroot/python/python/dist/src/Doc/ref
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv16053

Modified Files:
	ref5.tex 
Log Message:
SF patch #872326:  generator expression implementation
(Contributed by Jiwon Seo.)

Add genexps to the reference manual.



Index: ref5.tex
===================================================================
RCS file: /cvsroot/python/python/dist/src/Doc/ref/ref5.tex,v
retrieving revision 1.82
retrieving revision 1.83
diff -C2 -d -r1.82 -r1.83
*** ref5.tex	7 Aug 2004 19:16:32 -0000	1.82
--- ref5.tex	15 Aug 2004 23:28:10 -0000	1.83
***************
*** 56,60 ****
    \production{enclosure}
               {\token{parenth_form} | \token{list_display}}
!   \productioncont{| \token{dict_display} | \token{string_conversion}}
  \end{productionlist}
  
--- 56,61 ----
    \production{enclosure}
               {\token{parenth_form} | \token{list_display}}
!   \productioncont{| \token{generator_expression | \token{dict_display}}}
!   \productioncont{| \token{string_conversion}}
  \end{productionlist}
  
***************
*** 194,197 ****
--- 195,240 ----
  
  
+ \subsection{Generator expressions\label{genexpr}}
+ \indexii{generator}{expression}
+ 
+ A generator expression is a compact generator notation in parentheses:
+ 
+ \begin{productionlist}
+   \production{generator_expression}
+              {"(" \token{test} \token{genexpr_for} ")"}
+   \production{genexpr_for}
+              {"for" \token{expression_list} "in" \token{test}
+               [\token{genexpr_iter}]}
+   \production{genexpr_iter}
+              {\token{genexpr_for} | \token{genexpr_if}}
+   \production{genexpr_if}
+              {"if" \token{test} [\token{genexpr_iter}]}
+ \end{productionlist}
+ 
+ A generator expression yields a new generator object.
+ \obindex{generator}
+ \obindex{generator expression}
+ It consists of a single expression followed by at least one
+ \keyword{for} clause and zero or more \keyword{for} or \keyword{if}
+ clauses.  The iterating values of the new generator are those that
+ would be produced by considering each of the \keyword{for} or
+ \keyword{if} clauses a block, nesting from left to right, and
+ evaluating the expression to yield a value that is reached the
+ innermost block for each iteration.
+ 
+ Variables used in the generator expression are evaluated lazily
+ when the \method{next()} method is called for generator object
+ (in the same fashion as normal generators). However, the leftmost
+ \keyword{for} clause is immediately evaluated so that error produced
+ by it can be seen before any other possible error in the code that
+ handles the generator expression.
+ Subsequent \keyword{for} clauses cannot be evaluated immediately since
+ they may depend on the previous \keyword{for} loop.
+ For example: \samp{(x*y for x in range(10) for y in bar(x))}.
+ 
+ The parentheses can be omitted on calls with only one argument.
+ See section \ref{calls} for the detail.
+ 
+ 
  \subsection{Dictionary displays\label{dict}}
  \indexii{dictionary}{display}
***************
*** 433,436 ****
--- 476,481 ----
    \production{call}
               {\token{primary} "(" [\token{argument_list} [","]] ")"}
+              {\token{primary} "(" [\token{argument_list} [","] |
+ 	      \token{test} \token{genexpr_for} ] ")"}                                                   
    \production{argument_list}
               {\token{positional_arguments} ["," \token{keyword_arguments}]}