[antlr-interest] SOLVED Creation of Lexer and Parser in the loop? Bad idea

[Ruslan Zasukhin]

On 10/18/04 1:32 PM, "Ruslan Zasukhin" <sunshine at public.kherson.ua> wrote:

Hi All,

This task is solved, thanks to everybody who have help.


> Hi All,
> 
> I have note that we must write such code in C++
> 
> Foo( string SqlQuery )
> {
>   istringstream inp( SqlQuery.c_str() );
> 
> 
>   Lexer lex( inp );
>   Parser parser(lex);
> 
>   ..............
> }
> 
> 
> But if we look into constructor of Lexer we have
> 
> VSQL_Lexer::VSQL_Lexer(std::istream& in)
>   : antlr::CharScanner(new antlr::CharBuffer(in),false)
> {
>   initLiterals();
> }
> 
> void VSQL_Lexer::initLiterals()
> {
>   literals["words"] = 218;
>   literals["local"] = 212;
>   literals["blob"] = 111;
>   literals["byte"] = 89;
>   literals["action"] = 227;
>   literals["nullif"] = 144;
>   ..............
> }
> 
> 
> ---------------------------------------------
> I hope it is easy to see that Lexer must built the map for N elements.
> For big grammar this is few hundreds of items.
> 
> Guys, this is terrible!
> 
> For example, if I will do in the loop 100,000 or million SQL commands
>   INSERT INTO ...
> 
> Then I will need million times create/destroy objects of lexer and parer,
> And what is the worst I need million (!!!!!!) times create and fill THE SAME
> std::map. I believe this is just silly.
> 
> And I do not see that ANTLR can allow me create Lexer/Parser only once,
> And reuse them for different texts many times.
> Or I have miss something ?
> 
> 
> I am sure that this DESIGN MISTAKE must be fixed in the ANTLR.
> 
> Any comments? 
> Or advices how to reuse Lexer/Parser in huge loops?
> 
> And this is NOT theoretical tasks. SQL Server can get such loops very often.
> 

-- 
Best regards,
Ruslan Zasukhin      [ I feel the need...the need for speed ]
-------------------------------------------------------------
e-mail: ruslan at paradigmasoft.com
web: http://www.paradigmasoft.com

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