◆ read_n_to() [1/4]
Read a sequence of columns with given names or indices into existing Example usages: // Heterogeneous sequence (returns a tuple)
auto columns = ext.read_n(as<int>("A"), as<float, 2>("B"), as<std::string>("C"));
auto columns = ext.read_n(as<int>(0), as<float, 2>(3), as<std::string>(4));
// Homogeneous sequence (returns a vector)
auto columns = ext.read_n<int, 2>({"A", "B", "C"});
auto columns = ext.read_n<int, 2>({0, 3, 4});
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