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POHow to use a function from <cmath> with Boost.Lambda?
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2013-07-18T14:17:21.167
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I try to transform all elements of a vector <code>v</code> into their log values with some other arithmetic operations (not in the code). How can I use Boost.Lambda to achieve that? As I say, there are some more arithmetic operations, so an expression with Boost.Bind doesn't work for me (too complicated, too long, unreadable). I don't want to use C++11 lambdas as well. But... would it change anything? My code is like: <pre><code>#include <boost/lambda/lambda.hpp> #include <cmath> #include <vector> void testLambda() { using namespace boost::lambda; std::vector<double> v; v.push_back(1); v.push_back(2); v.push_back(3); std::transform(v.begin(), v.end(), v.begin(), _1 / 0.5); // works std::transform(v.begin(), v.end(), v.begin(), log(_1) / 0.5); // produces error //std::transform(v.begin(), v.end(), v.begin(), std::log(_1) / 0.5); // produces error //std::transform(v.begin(), v.end(), v.begin(), static_cast<double(*)(double)>(std::log)(_1) / 0.5); // produces error } </code></pre> When I try to compile the code, MSVC2010 gives the error: <pre><code>Error 1 error C2665: 'log' : none of the 3 overloads could convert all the argument types C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\include\math.h(120): could be 'double log(double)' C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\include\math.h(527): or 'float log(float)' C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\include\math.h(575): or 'long double log(long double)' while trying to match the argument list '(boost::lambda::placeholder1_type)' </code></pre> Update 1: I don't want to write functors for it, think that I would have to have a dozen of them, what then? Update 2: I am able to do it with C++11 lambdas, but it's not what I ask for: <pre><code> std::transform(v.begin(), v.end(), v.begin(), [](const double & x) { return log(x) / 0.5; }); </code></pre>
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<c++><boost><lambda>
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How to use a function from <cmath> with Boost.Lambda?
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