update from Peter Harris; minor edits

pep-0309.txt

@@ -1,5 +1,5 @@
 PEP: 309
-Title: Partial Function Application 
+Title: Partial Function Application
 Version: $Revision$
 Last-Modified: $Date$
 Author: Peter Harris <scav@blueyonder.co.uk>
@@ -18,15 +18,18 @@ This proposal is for a function or callable class that allows a new
 callable to be constructed from a callable and a partial argument list
 (including positional and keyword arguments).
 
-I propose a standard library module called "functional", to hold useful
+I propose a standard library module called "functional", to hold
-higher-order functions, including the implementation of partial().
+useful higher-order functions, including the implementation of
+partial().
+
+An implementation has been submitted to SourceForge [2]_.
 
 
 Motivation
 ==========
 
 In functional programming, function currying is a way of implementing
-multi-argument functions in terms of single-argument functions. A
+multi-argument functions in terms of single-argument functions.  A
 function with N arguments is really a function with 1 argument that
 returns another function taking (N-1) arguments.  Function application
 in languages like Haskell and ML works such that a function call::
@@ -38,7 +41,7 @@ actually means::
    (((f x) y) z)
 
 This would be only an obscure theoretical issue except that in actual
-programming it turns out to be very useful. Expressing a function in
+programming it turns out to be very useful.  Expressing a function in
 terms of partial application of arguments to another function can be
 both elegant and powerful, and in functional languages it is heavily
 used.
@@ -52,8 +55,9 @@ always knows the number of arguments expected and can do the right
 thing when presented with a functor and less arguments than expected.
 
 Python does not implement multi-argument functions by currying, so if
-you want a function with partially-applied arguments you would probably
+you want a function with partially-applied arguments you would
-use a lambda as above, or define a named function for each instance.
+probably use a lambda as above, or define a named function for each
+instance.
 
 However, lambda syntax is not to everyone's taste, so say the least.
 Furthermore, Python's flexible parameter passing using both positional
@@ -61,11 +65,11 @@ and keyword presents an opportunity to generalise the idea of partial
 application and do things that lambda cannot.
 
 
-Rationale
+Example Implementation
-=========
+======================
 
 Here is one way to do a create a callable with partially-applied
-arguments in Python. The implementation below is based on improvements
+arguments in Python.  The implementation below is based on improvements
 provided by Scott David Daniels::
 
     class partial(object):
@@ -90,6 +94,9 @@ positional arguments are appended to those provided to the
 constructor, and keyword arguments override and augment those provided
 to the constructor.
 
+Positional arguments, keyword arguments or both can be supplied at
+when creating the object and when calling it.
+
 
 Examples of Use
 ===============
@@ -97,8 +104,8 @@ Examples of Use
 So ``partial(operator.add, 1)`` is a bit like ``(lambda x: 1 + x)``.
 Not an example where you see the benefits, of course.
 
-Note too, that you could wrap a class in the same way, since
+Note too, that you could wrap a class in the same way, since classes
-classes themselves are callable factories for objects. So in some cases,
+themselves are callable factories for objects.  So in some cases,
 rather than defining a subclass, you can specialise classes by partial
 application of the arguments to the constructor.
 
@@ -115,9 +122,10 @@ callbacks for Tkinter widgets on the fly::
     win = Tk()
     c = Canvas(win,width=200,height=50)
     c.pack()
-    
+
     for colour in sys.argv[1:]:
-        b = Button(win, text=colour, command=partial(c.config,bg=colour))
+        b = Button(win, text=colour,
+                   command=partial(c.config, bg=colour))
         b.pack(side='left')
 
     win.mainloop()
@@ -129,16 +137,13 @@ Abandoned Syntax Proposal
 I originally suggested the syntax ``fn@(*args, **kw)``, meaning the
 same as ``partial(fn, *args, **kw)``.
 
-At least there are no backwards-compatibility issues because the @
-character isn't a legal operator in any previous versions of Python.
-
 The @ sign is used in some assembly languages to imply register
 indirection, and the use here is also a kind of indirection.
-``f@(x)`` is not ``f(x)`` , but a thing that becomes ``f(x)`` when you
+``f@(x)`` is not ``f(x)``, but a thing that becomes ``f(x)`` when you
 call it.
 
-It has not been well-received, so I have withdrawn this part of the
+It was not well-received, so I have withdrawn this part of the
-proposal.
+proposal.  In any case, @ has been taken for the new decorator syntax.
 
 
 Feedback from comp.lang.python and python-dev
@@ -157,7 +162,7 @@ Among the opinions voiced were the following (which I summarise):
 * A curry class would indeed be a useful addition to the standard
   library.
 
-* It isn't function currying, but partial application. Hence the
+* It isn't function currying, but partial application.  Hence the
   name is now proposed to be partial().
 
 * It maybe isn't useful enough to be in the built-ins.
@@ -181,7 +186,7 @@ not one single person has said they like it, so as far as I'm
 concerned it's a dead parrot.
 
 I concur with calling the class partial rather than curry or closure,
-so I have amended the proposal in this PEP accordingly. But not
+so I have amended the proposal in this PEP accordingly.  But not
 throughout: some incorrect references to 'curry' have been left in
 since that's where the discussion was at the time.
 
@@ -199,12 +204,10 @@ Carl Banks posted an implementation as a real functional closure::
             return fn(*(cargs + fargs), **d)
         return call_fn
 
-which he assures me is more efficient.  You lose introspection and
+which he assures me is more efficient.
-sub-classing that way, but these are maybe only marginal benefits and
-not worth a performance hit, so this would also do as a reference
-implementation.
 
-I also coded the class in Pyrex::
+I also coded the class in Pyrex, to estimate how the performance
+might be improved by coding it in C::
 
     cdef class curry:
 
@@ -238,10 +241,16 @@ callables should be present in the standard library.
 
 A standard library module ``functional`` should contain an
 implementation of ``partial``, and any other higher-order functions
-the community want. Other functions that might belong there fall
+the community want.  Other functions that might belong there fall
 outside the scope of this PEP though.
 
-The @ syntax proposal has been withrawn.
+Patches for the implementation, documentation and unit tests (SF
+patches 931005_, 931007_, and 931010_ respectively) have been
+submitted but not yet checked in.
+
+A C implementation by Hye-Shik Chang has also been submitted, although
+it is not expected to be included until after the Python
+implementation has proven itself useful enough to be worth optimising.
 
 
 References
@@ -249,6 +258,12 @@ References
 
 .. [1] http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52549
 
+.. [2] Patches 931005_, 931007_, and 931010_.
+
+.. _931005: http://www.python.org/sf/931005
+.. _931007: http://www.python.org/sf/931007
+.. _931010: http://www.python.org/sf/931010
+
 
 Copyright
 =========