C++ Mathematical Expression Library (ExprTk) https://www.partow.net/programming/exprtk/index.html
diff --git a/exprtk_simple_example_19.cpp b/exprtk_simple_example_19.cpp
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+/*
+ **************************************************************
+ * C++ Mathematical Expression Toolkit Library *
+ * *
+ * Simple Example 19 *
+ * Author: Arash Partow (1999-2016) *
+ * URL: http://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 Common Public License. *
+ * http://www.opensource.org/licenses/cpl1.0.php *
+ * *
+ **************************************************************
+*/
+
+
+#include <cstdio>
+#include <cstdlib>
+#include <ctime>
+#include <string>
+
+#include "exprtk.hpp"
+
+
+template <typename T>
+class randu : public exprtk::igeneric_function<T>
+{
+public:
+
+ typedef typename exprtk::igeneric_function<T> igfun_t;
+ typedef typename igfun_t::parameter_list_t parameter_list_t;
+ typedef typename igfun_t::generic_type generic_type;
+ typedef typename generic_type::vector_view vector_t;
+
+ using exprtk::igeneric_function<T>::operator();
+
+ randu()
+ : exprtk::igeneric_function<T>("V|VTT")
+ /*
+ Overloads:
+ 0. V - vector
+ 1. VTT - vector, r0, r1
+ */
+ { ::srand(static_cast<unsigned int>(time(NULL))); }
+
+ inline T operator()(const std::size_t& ps_index, parameter_list_t parameters)
+ {
+ vector_t v(parameters[0]);
+
+ std::size_t r0 = 0;
+ std::size_t r1 = v.size() - 1;
+
+ if (
+ (1 == ps_index) &&
+ !exprtk::rtl::vecops::helper::
+ load_vector_range<T>::process(parameters,r0,r1,1,2,0)
+ )
+ return T(0);
+
+ for (std::size_t i = r0; i <= r1; ++i)
+ {
+ v[i] = rnd();
+ }
+
+ return T(1);
+ }
+
+private:
+
+ inline T rnd()
+ {
+ // Note: Do not use this in production
+ // Result is in the interval [0,1)
+ return T(::rand() / T(RAND_MAX + 1.0));
+ }
+};
+
+template <typename T>
+void vector_randu()
+{
+ typedef exprtk::symbol_table<T> symbol_table_t;
+ typedef exprtk::expression<T> expression_t;
+ typedef exprtk::parser<T> parser_t;
+
+ std::string vecrandu_program =
+ " var noise[6] := [0]; "
+ " "
+ " if (randu(noise,0,5) == false) "
+ " { "
+ " println('Failed to generate noise'); "
+ " return [false]; "
+ " } "
+ " "
+ " var noisy[6] := signal + (noise - 1/2); "
+ " "
+ " for (var i := 0; i < noisy[]; i += 1) "
+ " { "
+ " println('noisy[',i,'] = ', noisy[i]); "
+ " } "
+ " "
+ " println('avg: ', avg(noisy)); "
+ " ";
+
+ T signal[] = { T(1.1), T(2.2), T(3.3), T(4.4), T(5.5), T(6.6), T(7.7) };
+
+ exprtk::rtl::io::println<T> println;
+ randu<T> randu;
+
+ symbol_table_t symbol_table;
+ symbol_table.add_vector ("signal" , signal);
+ symbol_table.add_function("println",println);
+ symbol_table.add_function("randu" , randu);
+
+ expression_t expression;
+ expression.register_symbol_table(symbol_table);
+
+ parser_t parser;
+ parser.compile(vecrandu_program,expression);
+
+ expression.value();
+}
+
+int main()
+{
+ vector_randu<double>();
+ return 0;
+}
