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

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 #include "boost/bind.hpp" #include #include 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 Cheers, Max On Tue, Jul 6, 2010 at 3:56 AM, Robert Jones wrote:

On Mon, Jul 5, 2010 at 9:18 PM, Max S. Kaznady wrote:

...

I followed the UBLAS extensions here:

http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl?Examples_-_Ho... and I figured out how to extend functions like "exp" and "log" to act on a vector.

But, those are functions of one argument. What I want is to be able to apply a function with one fixed argument, like std::pow, to a vector for some exponent exp, so I would like the code to look like: vector<double> v( 100 ); double exponent  = 2.1; // some exponent value // ... fill v ... std::cout << apply_to_all( v, functor::my_pow<double>(exponent) ) << std::endl; std::cout << apply_to_all( v ) << std::endl; OR std::cout << apply_to_all( v, functor::my_pow<double>() , exponent) << std::endl;

How can I do this? I tried overloading apply_to_all and writing constructor code, but it didn't work because the return type of the apply function is static.

P.S. I tried posting this to ublas lists, but got a message saying that my e-mail address is not registered. I guess that list is only for developers.

Hi Max

I'm not familiar with Ublas, but does this achieve the effect you're after

#include <vector> #include <algorithm> #include #include "boost/bind.hpp"

int main( ) {     std::vector<double> v;     double exponent = 2.1;     std::transform( v.begin(), v.end(), v.begin(), boost::bind( pow, _1, exponent ) ); }

Regards,

- Rob.

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