Re: Looking for Perl Grammar

* Khamis Abuelkomboz schrieb:
>
> However I still find clauses like
>
> if ( s{foo}{bar} ) ...
> if ( s[foo][var] ) ...
> if ( s<foo><bar> ) ...
>
> I still don't figure out what could be used as "brackets" for the
> s|tr|m commands???? So I'm looking as example for grammar descriping
> how the (s, tr, qq) could be built, something like
>
> S: s OP1 expr OP2 expr OP3
> OP1: '/' | '{' | '[' | ':' | ...
> OP2: '/' | '}{' | '][' | ...
> OP3: '/' | '}' | ']' | ':' | ...
>
> I'm still guissing :-)

This is mentioned in `perldoc perlop` in the section named "Quote and
Quote-like Operators".

Non-bracketing delimiters use the same character fore and aft, but
the four sorts of brackets (round, angle, square, curly) will all
nest, which means that

q{foo{bar}baz}

is the same as

'foo{bar}baz'

[...]

There can be whitespace between the operator and the quoting
characters, except when # is being used as the quoting character.
q#foo# is parsed as the string foo, while q #foo# is the operator q
followed by a comment. Its argument will be taken from the next
line. This allows you to write:

s {foo} # Replace foo
{bar} # with bar.

So, for s/// you could start with a grammar similar to

S: s WS BRACKETED WS BRACKETED | s WS DELIM expr DELIM expr DELIM
BRACKETED: '(' expr ')' | '<' expr '>' | '[' expr ']' | '{' expr '}'
WS: WHITE-SPACES *
DELIM: '/' | '!' | ':' | '^'

I'm not deeply familiar with grammar descriptions. Is there a way to
ensure that each DELIM is the same char?

Don't forget to add the special behavior of »#« to your grammar. And of
course, do you want to allow comments between the BRACKETED parts as in
the example above? ;-)

regards,
fabian
.

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