inverse_softmax.hpp

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#ifndef __STAN__MATH__FUNCTIONS__INVERSE_SOFTMAX_HPP__
#define __STAN__MATH__FUNCTIONS__INVERSE_SOFTMAX_HPP__

#include <boost/math/tools/promotion.hpp>
#include <stdexcept>
#include <boost/throw_exception.hpp>

namespace stan {
  namespace math {

    template <typename Vector>
    void inverse_softmax(const Vector& simplex, Vector& y) {
      using std::log;
      if(simplex.size() != y.size())
        BOOST_THROW_EXCEPTION(std::invalid_argument ("simplex.size() != y.size()"));
      for (size_t i = 0; i < simplex.size(); ++i)
        y[i] = log(simplex[i]);
    }

  }
}

#endif