"Alexander Borghgraef" wrote in message news:9e8c52a20509270717488cef04@mail.gmail.com...
On 9/27/05, Stuart Dootson wrote:
That's not going to work because the operator() call in the loop (i.e.
m(...)) is evaluated when the lambda expression is created, not each
time the lambda expression is evaluated.
Try replacing
var( m( c / m.w, c % m.w ) )
with
bind(&MyMatrix::operator(), var(m), var(c) / m->*&MyMatrix::w, var(c)
% m->*&MyMatrix::w)
This makes all accesses to m & c lazy (I think), so should update m as you want.
Ok, that fixes it. Now, hardcore algorithmism aside, I don't see any advantage in this over the
for loop: it's slower, and can hardly be called an improvement in readability. So I think I'll stick to
the old-fashioned syntax in this case. Still, interesting to know that boost::lambda actually can do
this.
Using std::copy and a function_output_iterator from the iterator adaptor library would IMHO, be more readable and resuable.
#include
struct matrix_filler
{
matrix_filler( matrix& m ): m(m), counter( 0 ) {}
void operator()( int val )const
{
m( counter / m.w , counter % m.w ) = val;
++counter
}
matrix& m;
long counter;
};
std::copy( v.begin(), v.end(), boost::make_function_output_iterator(matrix_filler(m)) );
Or provide a "linear" iterator to your matrix class.
Jeff Flinn
