RE: [boost] Re: lexicographic_less

From: Gary Powell (Gary.Powell_at_[hidden])
Date: 2000-06-08 17:06:14

> In my 
> particular case I'm trying to make a sort key out of a 'C' struct 
> which was defined externally, 
> 
> Lastly, I've been thinking that the ideal facility would allow the 
> user to choose the comparison operator/functor for each element being 
> compared (i.e. you might use std::less on the first element but 
> std::greater on the 2nd).
> 
So the part I don't get is, why not write the global
operator>(Cstruct,Cstruct), or a plain old functor? I don't see how your
infinitely adjustable set of classes makes the code any easier to read or
maintain. (Or it could be I need another cup of coffee...)

// TURN DAY DREAM ON.
IF C++ had a templated typedef, you could write it as a lambda statement.

template<class T>
  typedef lambda_statement<T>  CompareOperation;

struct C;

typedef containerType(C *, CompareOperation);

containerType container(CompareOperation(free1->*(&C::member1) >
free2->*(&C::member1)
                        && ....
) );

But without that typedef, (and some other hand waving) writing the lambda
typedef operation would be grounds for cruel and unusual punishment.

// TURN DAY DREAM OFF.

-gary-