choice.hpp

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#pragma once
 
#include <algorithm>
 
#include "NumCpp/Core/Enums.hpp"
#include "NumCpp/Core/Internal/Error.hpp"
#include "NumCpp/Core/Shape.hpp"
#include "NumCpp/Core/Types.hpp"
#include "NumCpp/NdArray.hpp"
#include "NumCpp/Random/permutation.hpp"
#include "NumCpp/Random/randInt.hpp"
 
namespace nc::random
{
    namespace detail
    {
        //============================================================================
        // Method Description:
        template<typename dtype, typename GeneratorType = std::mt19937>
        dtype choice(GeneratorType& generator, const NdArray<dtype>& inArray)
        {
            uint32 randIdx = detail::randInt<uint32>(generator, inArray.size());
            return inArray[randIdx];
        }
 
        //============================================================================
        // Method Description:
        template<typename dtype, typename GeneratorType = std::mt19937>
        NdArray<dtype> choice(GeneratorType&        generator,
                              const NdArray<dtype>& inArray,
                              uint32                inNum,
                              Replace               replace = Replace::YES)
        {
            if (replace == Replace::NO && inNum > inArray.size())
            {
                THROW_INVALID_ARGUMENT_ERROR("when Replace::NO 'inNum' must be <= inArray.size()");
            }
 
            if (replace == Replace::YES)
            {
                NdArray<dtype> outArray(1, inNum);
                std::for_each(outArray.begin(),
                              outArray.end(),
                              [&generator, &inArray](dtype& value) -> void { value = choice(generator, inArray); });
 
                return outArray;
            }
 
            return detail::permutation(generator, inArray)[Slice(inNum)];
        }
    } // namespace detail
 
    //============================================================================
    // Method Description:
    template<typename dtype>
    dtype choice(const NdArray<dtype>& inArray)
    {
        return detail::choice(generator_, inArray);
    }
 
    //============================================================================
    // Method Description:
    template<typename dtype>
    NdArray<dtype> choice(const NdArray<dtype>& inArray, uint32 inNum, Replace replace = Replace::YES)
    {
        return detail::choice(generator_, inArray, inNum, replace);
    }
} // namespace nc::random