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From: Benjamin Kaplan <benjamin.kaplan@case.edu>
Date: Tue, 22 Oct 2013 09:03:49 -0700
Subject: Re: Python Front-end to GCC
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On Tue, Oct 22, 2013 at 8:04 AM, Mark Janssen <dreamingforward@gmail.com> wrote:
> I love it.  Watch this...
>
> [context]
>>>> A language specification in BNF is just syntax. It doesn't say anything
>>>> about semantics. So how could this be used to produce executable C code
>>>> for a program? BNF is used to produce parsers. But a parser isn't
>>>> sufficient.
>>>
>>> A C program is just syntax also.  How does the compiler generate
>>> executable machine code?  Extrapolate into a Python front-end to C.
>
> [Dave Angel responds:]
>> Did you even read the paragraph you quoted above?  The BNF specification
>> does NOT completely describe a language, it only defines its syntax.
>
> [Steven D'Aprano responds:]
>> Like every other language, C programs are certainly not *just* syntax.
>> Here is some syntax:
>>
>> &foo bar^ :=
>
> Now, I don't know where y'all were taught Computer Science, but BNF
> specifies not only syntax (which would be the *tokens* of a language),
> but also its *grammar*;  how syntax relates to linguistic categories
> like keywords, and tokens relate to each other.
>
> Dave is claiming that BNF only defines the syntax of a language, but
> then Stephen goes on to supply some syntax that a BNF specification of
> the language would not allow (even though Steven calls it "syntax"
> which is what BNF in Dave's claim parses).
>
> So which of you is confused?  I ask that in the inclusive (not
> exclusive OR) sense.... ;^)  <-- face says "both".
>

I don't know where you were taught English, but syntax is " the way in
which linguistic elements (as words) are put together to form
constituents (as phrases or clauses) ", not the set of valid words
(tokens) in a language. A grammar, such as those grammars written in
BNF, describe the rules for the syntax of a language. And, as Steven
said, it still doesn't describe the semantics of a language, which is
the set of instructions described by the syntax.