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/* ************************************************************** * C++ Mathematical Expression Toolkit Library * * * * ExprTk Binomial Coefficient (n-choose-r) * * Author: Arash Partow (1999-2024) * * URL: https://www.partow.net/programming/exprtk/index.html * * * * Copyright notice: * * Free use of the Mathematical Expression Toolkit Library is * * permitted under the guidelines and in accordance with the * * most current version of the MIT License. * * https://www.opensource.org/licenses/MIT * * SPDX-License-Identifier: MIT * * * ************************************************************** */ #include #include #include "exprtk.hpp" template inline T ncr_println(T n, T r, T ncr) { printf("ncr(%2d,%2d) = %2llu\n", static_cast(n), static_cast(r), static_cast(ncr)); return T(0); } template void n_choose_r() { typedef exprtk::symbol_table symbol_table_t; typedef exprtk::expression expression_t; typedef exprtk::parser parser_t; typedef exprtk::function_compositor compositor_t; typedef typename compositor_t::function function_t; symbol_table_t symbol_table; symbol_table.add_function("println",ncr_println); compositor_t compositor(symbol_table); // define function: ncr(n,r) compositor.add( function_t("ncr") .vars("n", "r") .expression ( " switch " " { " " case n <= r : 1; " " case r <= 0 : 1; " " default : ncr(n - 1, r - 1) + " " ncr(n - 1, r ) ; " " } " )); const std::string ncr_program = " var n := 25; " " for (var r := 1; r < n; r += 1) " " { " " println(n, r, ncr(n,r)); " " }; "; expression_t expression; expression.register_symbol_table(symbol_table); parser_t parser; parser.compile(ncr_program,expression); expression.value(); } int main() { n_choose_r(); return 0; }