Re: Going backwards from a Language(or set of expressions) to a Grammar

Seima Rao <seimarao@gmail.com> wrote in news:17-04-014@comp.compilers:


> Hi,
>
> Is it possible generally to arrive at a grammar from
> a language or set of expressions ?


It depends on the language properties. It can be simple to impossible.


Your question implied that you thoroughly know the language and wanted
to derive its grammar sufficiently to write a parser/complier to
(correctly) process example programs/expressions.


An experienced compiler writer will need some time to study what
category of grammar is needed. (Regular) expressions just need an
lexical analyzer. Many languages like Pascal and Modula2 are LL-1 and
the grammars and parsers are straightforward recursive descent. Other
languages like C and its bethren need more complex bottom-up parsers
and preprocessors for disambiguation. Large context sensitive
languages (English for example) have a high error rate. So, your
answer is yes for simple with some practice and understanding and can
be extrememly had as the language gets complexity.


Elegant

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