[Python-checkins] python/dist/src/Doc/tut tut.tex,1.227,1.228

[rhettinger at users.sourceforge.net]

Update of /cvsroot/python/python/dist/src/Doc/tut
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv18118/Doc/tut

Modified Files:
	tut.tex 
Log Message:
Add more docs for generator expressions.

* Put in a brief, example driven tutorial entry.
* Use better examples in whatsnew24.tex.



Index: tut.tex
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RCS file: /cvsroot/python/python/dist/src/Doc/tut/tut.tex,v
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*** tut.tex	6 May 2004 01:35:45 -0000	1.227
--- tut.tex	19 May 2004 19:45:16 -0000	1.228
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*** 4400,4403 ****
--- 4400,4436 ----
  more effort than writing a regular function.
  
+ \section{Generator Expressions\label{genexps}}
+ 
+ Some simple generators can be coded succinctly as expressions using a syntax
+ like list comprehensions but with parentheses instead of brackets.  These
+ expressions are designed for situations where the generator is used right
+ away by an enclosing function.  Generator expressions are more compact but
+ less versatile than full generator definitions and the tend to be more memory
+ friendly than equivalent list comprehensions.
+ 
+ Examples:
+ 
+ \begin{verbatim}
+ >>> sum(i*i for i in range(10))                 # sum of squares
+ 285
+ 
+ >>> xvec = [10, 20, 30]
+ >>> yvec = [7, 5, 3]
+ >>> sum(x*y for x,y in zip(xvec, yvec))         # dot product
+ 260
+ 
+ >>> from math import pi, sin
+ >>> sine_table = dict((x, sin(x*pi/180)) for x in range(0, 91))
+ 
+ >>> unique_words = set(word  for line in page  for word in line.split())
+ 
+ >>> valedictorian = max((student.gpa, student.name) for student in graduates)
+ 
+ >>> data = 'golf'
+ >>> list(data[i] for i in range(len(data)-1,-1,-1))
+ ['f', 'l', 'o', 'g']
+ 
+ \end{verbatim}
+