Re: Using Standard C++ library with Bison .y files (or defining tokens with #define)...

[Hans Aberg]

Reply-to: address@hidden
At 20:30 +0100 2002/03/26, Michael Suodenjoki wrote:
>Hi,

Hi.

>I'm one of those C++ developers that's trying to use Bison to integrate
>a parser into a C++ project.

Akim will probably suggest you to try the CVS version and its C++ skeleton
file (I'm not a Bison developer).

>    %token eq

>This will in my version of the Standard C++ library FAIL because the
>'eq' is used inside the library (in my case in <iosfwd>, which have been
>included through <sstream>).

>1. Don't define token symbols that Standard C++ or any other include
>file may use. This may be a huge amount,
>and it is nearly impossible to know on beforehand. I know that the
>normal convention is to use uppercase
>tokens like EQ, however in principle these may be used elsewhere too.

Unless you find it difficult to type, have a computer really low on memory
or something, one can use longer names, for example:

%token equal_sign "="

%%
boolean_expression: lhs "=" rhs {...}

Bison error messages will then print "=", not "equal_sign".

>2. Change Bison so that it doesn't produces #defines but uses constants,
>e.g. like "const int eq = 257;"

I think that Bison's future C++ feature will do that, hopefully within a
custom namespace at need.

While waiting for that, you can emulate macro namespaces by adding a
prefix, for example

%token my_equal_sign "="

Apart from this change, provided you use "=", it does not change the
grammar code itself!

  Hans Aberg