[boost] Re: bind question/request

From: Andreas Huber (ah2003_at_[hidden])
Date: 2004-05-01 12:26:05

Max Khesin <MKhesin <at> liquidnet.com> writes:

> 
> I am refactoring code that looks something like this:
> 
>         if (op == LN::FILTER_IN || op == LN::FILTER_NOT_IN)
>         {
>             where += handle_set_operation(column, type, format, op,
> expr_set);
>         }
>         else if (op == LN::FILTER_RANGE)
>         {
>             where += handle_range_operation(column, type, format, op,
> expr_set);
>         }
>         else if (op == LN::FILTER_NULL || op == LN::FILTER_NOT_NULL)
>         {
>             where += handle_null_operation(column, op);
>         }
> 	  ...

I assume that you somewhere have a switch/case or multiple if/else if 
implementing dispatch on "where", before the above code is executed. If so, 
then this looks like the implementation of a state machine.

> This would obviously be handled better with a map of some sort (has to map
> int to function). The problem here is that some functions have more
> arguments than others, precluding the possibility of uniform type for the
> function value of the map. I cannot just go and change the function sig to
> include dummy values ('cause it's a dumb idea). This situation made me think
> of boost.function/boost.bind, which allows to effectively shorten the
> function parameter list by binding some of the args.

It seems that would be possible, but I think (given that I'm right about the 
state machine nature of your code) there are better ways to implement this. 
You might want to have a look at boost::fsm:

Docs only:

http://boost-sandbox.sf.net/libs/fsm

Code, examples and docs zipped:

http://boost-sandbox.sf.net/fsm.zip

Regards,

Andreas