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Signature	Description	Parameters
template<typename ... Ts> void truncate(IndexType &&before, IndexType &&after);	This removes data from the index column and all other data columns before the index value before and after the index value after. Before and after values are excluded. NOTE: It is assumed that the index column is sorted NOTE: Index type must have comparison operators (== != < > <= >=) well defined	Ts: List all the types of all data columns. A type should be specified in the list only once. before: An index value before which all data must be removed after: An index value after which all data must be removed

static void test_truncate()  {

    std::cout << "\nTesting truncate( ) ..." << std::endl;

    MyDataFrame                df;
    StlVecType<unsigned long>  idxvec = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 };
    StlVecType<double>         dblvec = { 0.0, 15.0, -14.0, 2.0, 1.0, 12.0, 11.0, 8.0, 7.0, 6.0, 5.0, 4.0, 3.0, 9.0, 10.0};
    StlVecType<double>         dblvec2 = { 100.0, 101.0, 102.0, 103.0, 104.0, 103.9, 106.55, 106.34, 1.8, 111.0, 112.0, 111.5, 114.0, 115.0, 116.0};
    StlVecType<std::string>    strvec = { "zz", "bb", "cc", "ww", "ee", "ff", "gg", "hh", "ii", "jj", "kk", "ll", "mm", "nn", "oo" };
    StlVecType<int>            intvec = { 1, 2, 3, 4, 5 };

    df.load_data(std::move(idxvec),
                 std::make_pair("dbl_col", dblvec),
                 std::make_pair("dbl_col_2", dblvec2),
                 std::make_pair("str_col", strvec));
    df.load_column("int_col", std::move(intvec), nan_policy::dont_pad_with_nans);

    {
        auto    df2 = df;

        StlVecType<unsigned long>  index = { 4, 5, 6, 7, 8, 9, 10, 11, 12 };
        StlVecType<double>         dbl_col = { 2, 1, 12, 11, 8, 7, 6, 5, 4 };
        StlVecType<double>         dbl_col_2 = { 103, 104, 103.9, 106.55, 106.34, 1.8, 111, 112, 111.5 };
        StlVecType<std::string>    str_col = { "ww", "ee", "ff", "gg", "hh", "ii", "jj", "kk", "ll" };
        StlVecType<int>            int_col = { 4, 5 };

        df2.truncate<double, std::string, int>(4, 12);
        assert(df2.get_index() == index);
        assert(df2.get_column<double>("dbl_col") == dbl_col);
        assert(df2.get_column<double>("dbl_col_2") == dbl_col_2);
        assert(df2.get_column<std::string>("str_col") == str_col);
        assert(df2.get_column<int>("int_col") == int_col);
    }
    {
        auto    df2 = df;

        StlVecType<unsigned long>  index = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };
        StlVecType<double>         dbl_col = { 0, 15, -14, 2, 1, 12, 11, 8, 7, 6, 5, 4 };
        StlVecType<double>         dbl_col_2 = { 100, 101, 102, 103, 104, 103.9, 106.55, 106.34, 1.8, 111, 112, 111.5 };
        StlVecType<std::string>    str_col = { "zz", "bb", "cc", "ww", "ee", "ff", "gg", "hh", "ii", "jj", "kk", "ll" };
        StlVecType<int>            int_col = { 1, 2, 3, 4, 5 };

        df2.truncate<double, std::string, int>(1, 12);
        assert(df2.get_index() == index);
        assert(df2.get_column<double>("dbl_col") == dbl_col);
        assert(df2.get_column<double>("dbl_col_2") == dbl_col_2);
        assert(df2.get_column<std::string>("str_col") == str_col);
        assert(df2.get_column<int>("int_col") == int_col);
    }
    {
        auto    df2 = df;

        StlVecType<unsigned long>  index = { 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 };
        StlVecType<double>         dbl_col = { 2, 1, 12, 11, 8, 7, 6, 5, 4, 3, 9, 10 };
        StlVecType<double>         dbl_col_2 = { 103, 104, 103.9, 106.55, 106.34, 1.8, 111, 112, 111.5, 114, 115, 116 };
        StlVecType<std::string>    str_col = { "ww", "ee", "ff", "gg", "hh", "ii", "jj", "kk", "ll", "mm", "nn", "oo" };
        StlVecType<int>            int_col = { 4, 5 };

        df2.truncate<double, std::string, int>(4, 15);
        assert(df2.get_index() == index);
        assert(df2.get_column<double>("dbl_col") == dbl_col);
        assert(df2.get_column<double>("dbl_col_2") == dbl_col_2);
        assert(df2.get_column<std::string>("str_col") == str_col);
        assert(df2.get_column<int>("int_col") == int_col);
    }
    {
        auto    df2 = df;

        StlVecType<unsigned long>  index = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 };
        StlVecType<double>         dbl_col = { 0, 15, -14, 2, 1, 12, 11, 8, 7, 6, 5, 4, 3, 9, 10 };
        StlVecType<double>         dbl_col_2 = { 100, 101, 102, 103, 104, 103.9, 106.55, 106.34, 1.8, 111, 112, 111.5, 114, 115, 116 };
        StlVecType<std::string>    str_col = { "zz", "bb", "cc", "ww", "ee", "ff", "gg", "hh", "ii", "jj", "kk", "ll", "mm", "nn", "oo" };
        StlVecType<int>            int_col = { 1, 2, 3, 4, 5 };

        df2.truncate<double, std::string, int>(0, 16);
    }
    {
        auto    df2 = df;

        StlVecType<unsigned long>  index = { 7, 8, 9, 10, 11, 12, 13, 14, 15 };
        StlVecType<double>         dbl_col = { 11, 8, 7, 6, 5, 4, 3, 9, 10 };
        StlVecType<double>         dbl_col_2 = { 106.55, 106.34, 1.8, 111, 112, 111.5, 114, 115, 116 };
        StlVecType<std::string>    str_col = { "gg", "hh", "ii", "jj", "kk", "ll", "mm", "nn", "oo" };
        StlVecType<int>            int_col = {  };

        df2.truncate<double, std::string, int>(7, 15);
        assert(df2.get_index() == index);
        assert(df2.get_column<double>("dbl_col") == dbl_col);
        assert(df2.get_column<double>("dbl_col_2") == dbl_col_2);
        assert(df2.get_column<std::string>("str_col") == str_col);
        assert(df2.get_column<int>("int_col") == int_col);
    }
}