On Fri, Nov 22, 2013 at 3:21 AM, anatoly techtonik <techto...@gmail.com>wrote:
> On Fri, Nov 15, 2013 at 5:43 PM, Benjamin Peterson <benja...@python.org> > wrote: > > 2013/11/15 anatoly techtonik <techto...@gmail.com>: > >> On Tue, Nov 12, 2013 at 5:08 PM, Benjamin Peterson <benja...@python.org> > wrote: > >>> 2013/11/12 anatoly techtonik <techto...@gmail.com>: > >>>> On Sun, Nov 10, 2013 at 8:34 AM, Benjamin Peterson < > benja...@python.org> wrote: > >>>>> 2013/11/10 anatoly techtonik <techto...@gmail.com>: > >>>>>> http://hg.python.org/cpython/file/1ee45eb6aab9/Parser/Python.asdl > >>>>>> > >>>>>> In Assign(expr* targets, expr value), why the first argument is a > list? > >>>>> > >>>>> x = y = 42 > >>>> > >>>> Thanks. > >>>> > >>>> Speaking of this ASDL. `expr* targets` means that multiple entities of > >>>> `expr` under the name 'targets' can be passed to Assign statement. > >>>> Assign uses them as left value. But `expr` definition contains things > >>>> that can not be used as left side assignment targets: > >>>> > >>>> expr = BoolOp(boolop op, expr* values) > >>>> | BinOp(expr left, operator op, expr right) > >>>> ... > >>>> | Str(string s) -- need to specify raw, unicode, etc? > >>>> | Bytes(bytes s) > >>>> | NameConstant(singleton value) > >>>> | Ellipsis > >>>> > >>>> -- the following expression can appear in assignment context > >>>> | Attribute(expr value, identifier attr, expr_context ctx) > >>>> | Subscript(expr value, slice slice, expr_context ctx) > >>>> | Starred(expr value, expr_context ctx) > >>>> | Name(identifier id, expr_context ctx) > >>>> | List(expr* elts, expr_context ctx) > >>>> | Tuple(expr* elts, expr_context ctx) > >>>> > >>>> If I understand correctly, this is compiled into C struct definitions > >>>> (Python-ast.c), and there is a code to traverse the structure, but > >>>> where is code that validates that the structure is correct? Is it done > >>>> on the first level - text file parsing, before ASDL is built? If so, > >>>> then what is the role of this ADSL exactly that the first step is > >>>> unable to solve? > >>> > >>> Only valid expression targets are allowed during AST construction. See > >>> set_expr_context in ast.c. > >> > >> Oh my. Now there is also CST in addition to AST. This stuff - > >> http://docs.python.org/devguide/ - badly needs diagrams about data > >> transformation toolchain from Python source code to machine > >> execution instructions. I'd like some pretty stuff, but raw blogdiag > >> hack will do the job http://blockdiag.com/en/blockdiag/index.html > >> > >> There is no set_expr_context in my copy of CPython code, which > >> seems to be some alpha of Python 3.4 > > > > It's actually called set_context. > > Ok. So what is the process? > > SOURCE --> TOKEN STREAM --> SENTENCE STREAM --> CST --> > --> AST --> BYTECODE > > Is that right? > > >>>> Is it possible to fix ADSL to move `expr` that are allowed in Assign > >>>> into `expr` subset? What effect will it achieve? I mean - will ADSL > >>>> compiler complain about wrong stuff on the left side, or it will still > >>>> be a role of some other component. Which one? > >>> > >>> I'm not sure what you mean by an `expr` subset. > >> > >> Transform this: > >> > >> expr = BoolOp(boolop op, expr* values) > >> | BinOp(expr left, operator op, expr right) > >> ... > >> | Str(string s) -- need to specify raw, unicode, etc? > >> | Bytes(bytes s) > >> | NameConstant(singleton value) > >> | Ellipsis > >> > >> -- the following expression can appear in assignment context > >> | Attribute(expr value, identifier attr, expr_context ctx) > >> | Subscript(expr value, slice slice, expr_context ctx) > >> | Starred(expr value, expr_context ctx) > >> | Name(identifier id, expr_context ctx) > >> | List(expr* elts, expr_context ctx) > >> | Tuple(expr* elts, expr_context ctx) > >> > >> to this: > >> > >> expr = BoolOp(boolop op, expr* values) > >> | BinOp(expr left, operator op, expr right) > >> ... > >> | Str(string s) -- need to specify raw, unicode, etc? > >> | Bytes(bytes s) > >> | NameConstant(singleton value) > >> | Ellipsis > >> > >> -- the following expression can appear in assignment context > >> | expr_asgn > >> > >> expr_asgn = > >> Attribute(expr value, identifier attr, expr_context ctx) > >> | Subscript(expr value, slice slice, expr_context ctx) > >> | Starred(expr value, expr_context ctx) > >> | Name(identifier id, expr_context ctx) > >> | List(expr* elts, expr_context ctx) > >> | Tuple(expr* elts, expr_context ctx) > > > > I doubt ASDL will let you do that. > > asdl.py is plain broken - wrong number of arguments passed to > output function > asdl_c.py worked ok with fixed ASDL and generated - diff attached. > I don't know what to check further - on Windows without Visual Studio. > -- > asdl.py is about to be replaced - please see http://bugs.python.org/issue19655 - I'm waiting for after the 3.4 branch to move forward with that. Let's discuss any needed fixes in that issue. Eli
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