| 25 | |
| 26 | template <typename T> |
| 27 | void square_wave() |
| 28 | { |
| 29 | typedef exprtk::symbol_table<T> symbol_table_t; |
| 30 | typedef exprtk::expression<T> expression_t; |
| 31 | typedef exprtk::parser<T> parser_t; |
| 32 | |
| 33 | const std::string expression_string = |
| 34 | "a *(4 / pi) * " |
| 35 | "((1 / 1) * sin( 2 * pi * f * t) + (1 / 3) * sin( 6 * pi * f * t) + " |
| 36 | " (1 / 5) * sin(10 * pi * f * t) + (1 / 7) * sin(14 * pi * f * t) + " |
| 37 | " (1 / 9) * sin(18 * pi * f * t) + (1 / 11) * sin(22 * pi * f * t) + " |
| 38 | " (1 / 13) * sin(26 * pi * f * t) + (1 / 15) * sin(30 * pi * f * t) + " |
| 39 | " (1 / 17) * sin(34 * pi * f * t) + (1 / 19) * sin(38 * pi * f * t) + " |
| 40 | " (1 / 21) * sin(42 * pi * f * t) + (1 / 23) * sin(46 * pi * f * t) + " |
| 41 | " (1 / 25) * sin(50 * pi * f * t) + (1 / 27) * sin(54 * pi * f * t)) "; |
| 42 | |
| 43 | static const T pi = T(3.141592653589793238462643383279502); |
| 44 | |
| 45 | const T f = pi / T(10); |
| 46 | const T a = T(10); |
| 47 | T t = T(0); |
| 48 | |
| 49 | symbol_table_t symbol_table; |
| 50 | symbol_table.add_variable("t",t); |
| 51 | symbol_table.add_constant("f",f); |
| 52 | symbol_table.add_constant("a",a); |
| 53 | symbol_table.add_constants(); |
| 54 | |
| 55 | expression_t expression; |
| 56 | expression.register_symbol_table(symbol_table); |
| 57 | |
| 58 | parser_t parser; |
| 59 | parser.compile(expression_string,expression); |
| 60 | |
| 61 | const T delta = (T(4) * pi) / T(1000); |
| 62 | |
| 63 | for (t = (T(-2) * pi); t <= (T(+2) * pi); t += delta) |
| 64 | { |
| 65 | const T result = expression.value(); |
| 66 | printf("%19.15f\t%19.15f\n", t, result); |
| 67 | } |
| 68 | } |
| 69 | |
| 70 | int main() |
| 71 | { |