[Python-checkins] CVS: python/nondist/peps pep-0279.txt,1.2,1.3

2002年2月04日 13:03:06 -0800

Update of /cvsroot/python/python/nondist/peps
In directory usw-pr-cvs1:/tmp/cvs-serv9926
Modified Files:
	pep-0279.txt 
Log Message:
Raymond Hettinger's latest updates.
Index: pep-0279.txt
===================================================================
RCS file: /cvsroot/python/python/nondist/peps/pep-0279.txt,v
retrieving revision 1.2
retrieving revision 1.3
diff -C2 -d -r1.2 -r1.3
*** pep-0279.txt	2002年02月01日 14:55:46	1.2
--- pep-0279.txt	2002年02月04日 21:03:03	1.3
***************
*** 8,12 ****
 Created: 30-Jan-2002
 Python-Version: 2.3
! Post-History: 

--- 8,12 ----
 Created: 30-Jan-2002
 Python-Version: 2.3
! Post-History:

***************
*** 46,50 ****
 making generator creation as convenient as list creation.

! 3. Extend the syntax of the 'yield' keyword to enable two way
 parameter passing. The resulting increase in power simplifies
 the creation of consumer streams which have a complex execution
--- 46,50 ----
 making generator creation as convenient as list creation.

! 3. Extend the syntax of the 'yield' keyword to enable generator
 parameter passing. The resulting increase in power simplifies
 the creation of consumer streams which have a complex execution
***************
*** 58,62 ****
 existing implementation and require little additional effort to
 incorporate. Each is backward compatible and requires no new
! keywords.

--- 58,63 ----
 existing implementation and require little additional effort to
 incorporate. Each is backward compatible and requires no new
! keywords. These generator tools go into Python 2.3 when
! generators become final and are not imported from __future__.

***************
*** 150,180 ****

 If a list comprehension starts with a 'yield' keyword, then
! express the remainder of the statement as generator. For example:

! g = [yield (len(line),line) for line in file.readline() if len(line)>5]
! print g.next()
! print g.next()

 This would be implemented as if it had been written:

! def __temp_gen():
! for line in file.readline():
! if len(line) > 5:
! yield (len(line), line)
! g = __temp_gen()
! print g.next()
! print g.next()
! 
! Note A: There is a difference in the above implementation as
! compared to list comprehensions. For a generator comprehension,
! the variables are created in a separate scope while list
! comprehensions use the enclosing scope. If this PEP is accepted,
! the parser should generate byte code that eliminates this
! difference by passing the line variable in the enclosing scope and
! using that same variable passed by reference inside the generator.
! This will make the behavior of generator comprehension identical
! to that of list comprehensions.

! Note B: There is some debate about whether the enclosing brackets
 should be part of the syntax for generator comprehensions. On the
 plus side, it neatly parallels list comprehensions and would be
--- 151,168 ----

 If a list comprehension starts with a 'yield' keyword, then
! express the comprehension with a generator. For example:

! g = [yield (len(line),line) for line in file if len(line)>5]

 This would be implemented as if it had been written:

! class __Temp:
! def __iter__(self):
! for line in file:
! if len(line) > 5:
! yield (len(line), line)
! g = __Temp()

! Note A: There is some debate about whether the enclosing brackets
 should be part of the syntax for generator comprehensions. On the
 plus side, it neatly parallels list comprehensions and would be
***************
*** 191,195 ****

! Specification for two-way Generator Parameter Passing:

 1. Allow 'yield' to assign a value as in:
--- 179,183 ----

! Specification for Generator Parameter Passing:

 1. Allow 'yield' to assign a value as in:
***************
*** 210,214 ****
 is that a value can be sent into the generator. By analogy,
 consider the quality improvement from GOSUB (which had no argument
! passing mechanism) to modern procedure calls (which pass in
 arguments and return values).

--- 198,202 ----
 is that a value can be sent into the generator. By analogy,
 consider the quality improvement from GOSUB (which had no argument
! passing mechanism) to modern procedure calls (which can pass in
 arguments and return values).

***************
*** 235,239 ****
 queues. A class-based approach competes well when there are no
 complex execution states or variable states. When the complexity
! increases, generators with two-way communication are much simpler
 because they automatically save state (unlike classes which must
 explicitly save the variable and execution state in instance
--- 223,227 ----
 queues. A class-based approach competes well when there are no
 complex execution states or variable states. When the complexity
! increases, generators with parameter passing are much simpler
 because they automatically save state (unlike classes which must
 explicitly save the variable and execution state in instance
***************
*** 241,245 ****

! Example of a Complex Consumer 

 The encoder for arithmetic compression sends a series of
--- 229,233 ----

! Example of a Complex Consumer

 The encoder for arithmetic compression sends a series of
***************
*** 282,285 ****
--- 270,282 ----

+ Example of a Producer and Consumer Used Together in a Pipelike Fashion
+ 
+ 'Analogy to: source | upper | sink'
+ sink = sinkgen()
+ sink.next()
+ for word in source():
+ sink.next( word.upper() )
+ 
+ 
 Specification for Generator Exception Passing:

***************
*** 312,318 ****
 already associated with exceptions in other languages.

 References
! 
 [1] PEP 255 Simple Generators
 http://python.sourceforge.net/peps/pep-0255.html
--- 309,322 ----
 already associated with exceptions in other languages.

+ Note B: The throw syntax should exactly match raise's syntax including:
+ raise string g.throw(string)
+ raise string, data g.throw(string,data)
+ raise class, instance g.throw(class,instance)
+ raise instance g.throw(instance)
+ raise g.throw()

+ 
 References
! 
 [1] PEP 255 Simple Generators
 http://python.sourceforge.net/peps/pep-0255.html
***************
*** 321,325 ****
 http://python.sourceforge.net/peps/pep-0212.html

! [3] PEP 202 List Comprehensions 
 http://python.sourceforge.net/peps/pep-0202.html

--- 325,329 ----
 http://python.sourceforge.net/peps/pep-0212.html

! [3] PEP 202 List Comprehensions
 http://python.sourceforge.net/peps/pep-0202.html

***************
*** 327,331 ****
 tease out these proposals:

! Indexed Function 
 http://groups.google.com/groups?hl=en&th=33f778d92dd5720a

--- 331,335 ----
 tease out these proposals:

! Indexed Function
 http://groups.google.com/groups?hl=en&th=33f778d92dd5720a

***************
*** 340,347 ****

 Discussion Draft of this PEP
! http://groups.google.com/groups?hl=en&th=df8b5e7709957eb7 

 [5] Dr. David Mertz's draft column for Charming Python.
! href="http://gnosis.cx/publish/programming/charming_python_b5.txt

--- 344,351 ----

 Discussion Draft of this PEP
! http://groups.google.com/groups?hl=en&th=df8b5e7709957eb7

 [5] Dr. David Mertz's draft column for Charming Python.
! http://gnosis.cx/publish/programming/charming_python_b5.txt

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*** 357,358 ****
--- 361,364 ----
 fill-column: 70
 End:
+ 
+ 