(original) (raw)

2013/11/22 anatoly techtonik <techtonik@gmail.com>:

> On Fri, Nov 15, 2013 at 5:43 PM, Benjamin Peterson <benjamin@python.org> wrote:
\>> 2013/11/15 anatoly techtonik <techtonik@gmail.com>:
\>>> On Tue, Nov 12, 2013 at 5:08 PM, Benjamin Peterson <benjamin@python.org> wrote:
\>>>> 2013/11/12 anatoly techtonik <techtonik@gmail.com>:
\>>>>> On Sun, Nov 10, 2013 at 8:34 AM, Benjamin Peterson <benjamin@python.org> wrote:
\>>>>>> 2013/11/10 anatoly techtonik <techtonik@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.