RE: [boost] Review: Lambda library - more technical analysis

From: Asger Alstrup Nielsen (alstrup_at_[hidden])
Date: 2002-03-25 08:13:18

> [3]
> 
> std::find_if(v.begin(), v.end(), _1 > 5);
> 
> Which one do you prefer?

I prefer 3. 

This is not relevant to my critique. Please read what I have written
once more, and point out what is not clear.

It might help to illustrate one of my points by writing the following as
an anonymous lambda expression:

int foo(int i) {
        switch (i) {
        case 0: return i + 1;
        case 1: 
                try {
                        return bar(i + 3);
                } catch(...) {
                        return -1;
                }
        default:
                if (i < 10) {
                        return i;
                } else {
                        int j = i;
                        while (i > 100) {
                                j += i;
                                i /= 2;
                        }
                        return j;
                }
        }
}

My initial try to write this with LL is this:

int j;
std::for_each(v.begin(), v.end(), 
        switch_statement(_1,
                case_statement<0>(_1 + 1),
                case_statement<1>(try_catch( 
                                                bar(_1 + 3),
                                        catch_all(-1)
                                        )
                ),
                default_statement(if_then_else(_1 < 10, 
                                                1,
                                                ( j = 1, 
                                                  while_statement(_1 <
100, 
                                                        (j += _1, 
                                                         i /= 2
                                                        ) 
                                                ), 
                                                j)
                                        )
                )
        );
);

I can't check it because I'm stuck with VC6, but there is at least one
error in the above. Can you spot it?

I do not think this style of programming is something to encourage.

I much prefer the basic lambda library with only basic expression
support, assignment, scoping and boost::function interaction.

Greets,

Asger Alstrup Nielsen