On Fri, Nov 22, 2013 at 7:29 AM, Benjamin Peterson <benja...@python.org>wrote:
> 2013/11/22 anatoly techtonik <techto...@gmail.com>: > > 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? > > I don't know what sentence stream is, but otherwise looks right. If you want more of an overview: http://pyvideo.org/video/2331/from-source-to-code-how-cpythons-compiler-works
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