Re: Token redefinition

[Tim Van Holder]

Hans Aberg wrote:
> On 16 Nov 2006, at 11:41, Giampaolo Fadel wrote:
> 
>> I need to write a simple compiler for a pascal-like linguage, using
>> flex and bison.
>> The language uses token as "INT" "BOOL" or "FALSE"; when I compile the
>> project using
>> Visual Studio 6.0 the following message is displayed:
>>
>> "'BOOL' : redefinition; typedef cannot be overloaded with any other
>> symbol"
>>
>> This is because in windef.h they are other defines of tokens "INT"
>> "BOOL" or "FALSE".
>> How can I resolve the question WITHOUT change the names of the tokens ??
> 
> You can switch to a different platform.

Or, as a more constructive suggestion, you could use a prefix for the
token names in the grammar (T_BOOL, tBool, tokBOOL, etc. are all viable
alternatives).  And you can always give them string names you use in the
grammar:

grammar:   %token t_BOOL "BOOL"
lexer:     "BOOL" { return t_BOOL; }
grammar:   some_rule: some_other_rule "BOOL";

which ensures that bison syntax errors say they expect a BOOL rather
than a t_BOOL (only the lexer has to use the t_* names). This is
especially nice when the name for the token consists of multiple words:

%token t_DECIMAL_LITERAL "decimal literal"