[Proj] proj.4 BNF

[support.mn at elisanet.fi]

The problem using + alone as a staement separator is obvious,
since it can be mixed with positive number sign. One way is to forbid
to use "+" as a positive number sgn. But then it would trop all
future expressions also. Maybe best is to agree, that if "+" is
used as statement separator (and continuation mark) it should
be preceded by <SEP>, which is usually the case.

So it would be more like:


<SEP> ::= (<SPACE>  | <TAB> | <EOL>) {<SEP>}

<continuation> ::= <SEP> "+"


That would require some white space before + and would make it
most clear?

----

Janne.

-----------------------------------------

support.mn at elisanet.fi kirjoitti: 
> Frank Warmerdam <warmerdam at pobox.com> kirjoitti: 
> > support.mn at elisanet.fi wrote:
> > > Maybe should define the correct BNF (BackusNaur Form) for proj.4?
> > > 
> > > http://en.wikipedia.org/wiki/Backus-Naur_form
> > > 
> > > That would help people to write correct proj.4 inits. I am still wondering
> > > that if sombody enters wrong proj.4 attributes, the library takes them 
> > > in, but does
> > > something else and never informs the user that something he was entering
> > > was totally ignored. Not a very nice situation.
> > > 
> > > There might be some kind of a stand alone pre scanner, that could be called
> > > on demand and that checked the user entry and gave full information about
> > > typos. errors and similar matters. It could be bypassed by those who do not
> > > need it. But I don't see why anybody wanted to bypass checking of his 
> > > input.
> > 
> > Janne,
> > 
> > While this seems like a reasonable idea, I am doubtful that it will occur
> > due to the challenges in implementing and keeping it up to date.
> > 
> 
> Well, I can start with it. Here is an example, maybe full of errors, but something
> to start with.
> 
> ------------------
> 
> <proj.4 definition> ::= <statement list>
> 
> <statement list> ::= <statement> {<SEP> <statement list> }
> 
> <statement> ::= <empty> | <comment line> | <assignment statement> | <identifier>
> 
> <empty ::=
> 
> <comment line> ::= # <anything but EOL> <EOL>
> 
> <assignment statement> ::= <identifier> = <right side>
> 
> <right side> ::= <identifier> | <identifier list> | <number> | <number list>
> 
> ........
> 
> <EOL> ::= <CR> <LF> | <CR> | <LF>
> 
> <SEP> ::= <SPACE>  | <TAB> | <EOL> | "+"
> 
> <SPACE>  :: = " "
> 
> <TAB>  ::= chr(09)
> 
> 
> etc. etc.
> 
> 
> 
> regards: Janne.