Re: [Boost-users] apply std::pow to vector or matrix

Subject: Re: [Boost-users] apply std::pow to vector or matrix
From: Robert Jones (robertgbjones_at_[hidden])
Date: 2010-07-07 03:06:55

On Wed, Jul 7, 2010 at 3:30 AM, Max S. Kaznady <max.kaznady_at_[hidden]>wrote:

> Hi Robert,
>
> Yep, the following works great. Not sure why the same code doesn't
> work when I have it in my larger project, but I guess that's for me to
> figure out.
>
> There is still the problem with the std::for_each, see below:
>
> #include <iostream>
> #include <vector>
> #include <algorithm>
> #include <math.h>
> #include "boost/bind.hpp"
> #include <boost/numeric/ublas/vector.hpp>
> #include <boost/numeric/ublas/io.hpp>
>
> int main( )
> {
>  boost::numeric::ublas::vector<double> v(10);
>  double exponent = 2.1;
>  std::fill(v.begin(), v.end(), 8.0);
>  // The following works just fine:
>   std::transform( v.begin(), v.end(), v.begin(), boost::bind( pow, _1,
> exponent ) );
>   // But the for_each doesn't apply the power function, just leaves
> the vector unaltered
>  std::for_each( v.begin(), v.end(), boost::bind( pow, _1, exponent ) );
>  // Print the result
>  std::cout<< v << std::endl;
>
>  return 0;
> }
>
> Compiled with: g++ -O2 -Wfatal-errors -Wall -g -ansi
> -I/usr/local/boost/include -o main main.cpp
>
>
Hi Max

I haven't taken the time to try this, but does this do the trick?

std::for_each(v.begin(), v.end(), boost::bind(pow, boost::ref(_1),
exponent));

Cheers

- Rob.