The additional code complexity and new NOP opcode were not worth it.

* Can now test for basic blocks.
* Optimize inverted comparisions.
* Optimize unary_not followed by a conditional jump.
* Added a new opcode, NOP, to keep code size constant.
* Applied NOP to previous transformations where appropriate.

Note, the NOP would not be necessary if other functions were
added to re-target jump addresses and update the co_lnotab mapping.
That would yield slightly faster and cleaner bytecode at the
expense of optimizer simplicity and of keeping it decoupled
from the line-numbering structure.

Use a slightly different strategy to determine when not to call the line
trace function.  This removes the need for the RETURN_NONE opcode, so
that's gone again.  Update docs and comments to match.

Thanks to Neal and Armin!

Also add a test suite.  This should have come with the original patch...

[ 587993 ] SET_LINENO killer

Remove SET_LINENO.  Tracing is now supported by inspecting co_lnotab.

Many sundry changes to document and adapt to this change.

This introduces:

- A new operator // that means floor division (the kind of division
  where 1/2 is 0).

- The "future division" statement ("from __future__ import division)
  which changes the meaning of the / operator to implement "true
  division" (where 1/2 is 0.5).

- New overloadable operators __truediv__ and __floordiv__.

- New slots in the PyNumberMethods struct for true and floor division,
  new abstract APIs for them, new opcodes, and so on.

I emphasize that without the future division statement, the semantics
of / will remain unchanged until Python 3.0.

Not yet implemented are warnings (default off) when / is used with int
or long arguments.

This has been on display since 7/31 as SF patch #443474.

Flames to /dev/null.

Bugfix candidate in inspect.py:  it was referencing "self" outside of
a method.

new slot tp_iter in type object, plus new flag Py_TPFLAGS_HAVE_ITER
new C API PyObject_GetIter(), calls tp_iter
new builtin iter(), with two forms: iter(obj), and iter(function, sentinel)
new internal object types iterobject and calliterobject
new exception StopIteration
new opcodes for "for" loops, GET_ITER and FOR_ITER (also supported by dis.py)
new magic number for .pyc files
new special method for instances: __iter__() returns an iterator
iteration over dictionaries: "for x in dict" iterates over the keys
iteration over files: "for x in file" iterates over lines

TODO:

documentation
test suite
decide whether to use a different way to spell iter(function, sentinal)
decide whether "for key in dict" is a good idea
use iterators in map/filter/reduce, min/max, and elsewhere (in/not in?)
speed tuning (make next() a slot tp_next???)

SF patch 102989 by Thomas Wouters

The majority of the changes are in the compiler.  The mainloop changes
primarily to implement the new opcodes and to pass a function's
closure to eval_code2().  Frames and functions got new slots to hold
the closure.

Include/compile.h
    Add co_freevars and co_cellvars slots to code objects.
    Update PyCode_New() to take freevars and cellvars as arguments
Include/funcobject.h
    Add func_closure slot to function objects.
    Add GetClosure()/SetClosure() functions (and corresponding
    macros) for getting at the closure.
Include/frameobject.h
    PyFrame_New() now takes a closure.
Include/opcode.h
    Add four new opcodes: MAKE_CLOSURE, LOAD_CLOSURE, LOAD_DEREF,
    STORE_DEREF.
    Remove comment about old requirement for opcodes to fit in 7
    bits.
compile.c
    Implement changes to code objects for co_freevars and co_cellvars.

    Modify symbol table to use st_cur_name (string object for the name
    of the current scope) and st_cur_children (list of nested blocks).
    Also define st_nested, which might more properly be called
    st_cur_nested.  Add several DEF_XXX flags to track def-use
    information for free variables.

    New or modified functions of note:
    com_make_closure(struct compiling *, PyCodeObject *)
        Emit LOAD_CLOSURE opcodes as needed to pass cells for free
        variables into nested scope.
    com_addop_varname(struct compiling *, int, char *)
        Emits opcodes for LOAD_DEREF and STORE_DEREF.
    get_ref_type(struct compiling *, char *name)
        Return NAME_CLOSURE if ref type is FREE or CELL
    symtable_load_symbols(struct compiling *)
        Decides what variables are cell or free based on def-use info.
        Can now raise SyntaxError if nested scopes are mixed with
        exec or from blah import *.
    make_scope_info(PyObject *, PyObject *, int, int)
        Helper functions for symtable scope stack.
    symtable_update_free_vars(struct symtable *)
        After a code block has been analyzed, it must check each of
        its children for free variables that are not defined in the
        block.  If a variable is free in a child and not defined in
        the parent, then it is defined by block the enclosing the
        current one or it is a global.  This does the right logic.
    symtable_add_use() is now a macro for symtable_add_def()
    symtable_assign(struct symtable *, node *)
        Use goto instead of for (;;)

    Fixed bug in symtable where name of keyword argument in function
    call was treated as assignment in the scope of the call site. Ex:
        def f():
            g(a=2) # a was considered a local of f

ceval.c
    eval_code2() now take one more argument, a closure.
    Implement LOAD_CLOSURE, LOAD_DEREF, STORE_DEREF, MAKE_CLOSURE>

    Also: When name error occurs for global variable, report that the
    name was global in the error mesage.

Objects/frameobject.c
    Initialize f_closure to be a tuple containing space for cellvars
    and freevars.  f_closure is NULL if neither are present.
Objects/funcobject.c
    Add support for func_closure.
Python/import.c
    Change the magic number.
Python/marshal.c
    Track changes to code objects.

This should match the situation in the 1.6b1 tree.

PySequence methods and functions, new tokens.

Add the EXTENDED_ARG opcode to the virtual machine, allowing 32-bit
arguments to opcodes instead of being forced to stick to the 16-bit
limit.  This is especially useful for machine-generated code, which
can be too long for the SET_LINENO parameter to fit into 16 bits.

This closes the implementation portion of SourceForge patch #100893.

This adds the two new opcodes to support this feature: PRINT_ITEM_TO,
PRINT_NEWLINE_TO.

name as n'. By doing some twists and turns, "as" is not a reserved word.

There is a slight change in semantics for 'from module import name' (it will
now honour the 'global' keyword) but only in cases that are explicitly
undocumented.

did the same anyway.

I'm not sure what to do with Tools/compiler/compiler/* -- that isn't part of
distutils, is it ? Should it try to be compatible with old bytecode version ?

executive summary:
Instead of typing 'apply(f, args, kwargs)' you can type 'f(*arg, **kwargs)'.
Some file-by-file details follow.

Grammar/Grammar:
    simplify varargslist, replacing '*' '*' with '**'
    add * & ** options to arglist

Include/opcode.h & Lib/dis.py:
    define three new opcodes
        CALL_FUNCTION_VAR
        CALL_FUNCTION_KW
        CALL_FUNCTION_VAR_KW

Python/ceval.c:
    extend TypeError "keyword parameter redefined" message to include
        the name of the offending keyword
    reindent CALL_FUNCTION using four spaces
    add handling of sequences and dictionaries using extend calls
    fix function import_from to use PyErr_Format

object.h: made sizes and refcnts signed ints.
stringobject.h: make getstrsize() signed int.
methodobject.h: add METH_VARARGS and METH_FREENAME flag bit definitions.

* Grammar: add exec statement; allow testlist in expr statement.
* ceval.c, compile.c, opcode.h: support exec statement;
  avoid optimizing locals when it is used
* fileobject.{c,h}: add getfilename() internal function.

* Makefile: change location of FORMS library.
* posixmodule.c: turn #if 0 into #ifdef MSDOS (stuff in unistd.h or not)
* Almost all .h files: added CPP magic to avoid duplicate inclusions and
  to support inclusion from C++.

(1) dictionaries/mappings now have attributes values() and items() as
well as keys(); at the C level, use the new function mappinggetnext()
to iterate over a dictionary.

(2) "class C(): ..." is now illegal; you must write "class C: ...".

(3) Class objects now know their own name (finally!); and minor
improvements to the way how classes, functions and methods are
represented as strings.

(4) Added an "access" statement and semantics.  (This is still
experimental -- as long as you don't use the keyword 'access' nothing
should be changed.)

lookup (opcode.h, ceval.[ch], compile.c, frameobject.[ch],
pythonrun.c, import.c).  The .pyc MAGIC number is changed again.
Added get_menu_text to flmodule.

* Stubs for faster implementation of local variables (not yet finished)
* Added function name to code object.  Print it for code and function
  objects.  THIS MAKES THE .PYC FILE FORMAT INCOMPATIBLE (the version
  number has changed accordingly)
* Print address of self for built-in methods
* New internal functions getattro and setattro (getattr/setattr with
  string object arg)
* Replaced "dictobject" with more powerful "mappingobject"
* New per-type functio tp_hash to implement arbitrary object hashing,
  and hashobject() to interface to it
* Added built-in functions hash(v) and hasattr(v, 'name')
* classobject: made some functions static that accidentally weren't;
  added __hash__ special instance method to implement hash()
* Added proper comparison for built-in methods and functions