example.cc

// Simple example file for the function parser
// ===========================================

/* When running the program, try for example with these values:

f(x) = x^2
min x: -5
max x: 5
step: 1

*/

#include "fparser.hh"

#include <iostream>
#include <string>

int main() {
    std::string function;
    double minx, maxx, step;
    FunctionParser fparser;

    fparser.AddConstant("pi", 3.1415926535897932);

    while (true) {
        std::cout << "f(x) = ";
        std::getline(std::cin, function);
        if (std::cin.fail()) return 0;

        int res = fparser.Parse(function, "x");
        if (res < 0) break;

        std::cout << std::string(res + 7, ' ') << "^\n"
                  << fparser.ErrorMsg() << "\n\n";
    }

    std::cout << "min x: ";
    std::cin >> minx;
    std::cout << "max x: ";
    std::cin >> maxx;
    std::cout << "step: ";
    std::cin >> step;
    if (std::cin.fail()) return 0;

    double vals[] = {0};
    for (vals[0] = minx; vals[0] <= maxx; vals[0] += step) {
        std::cout << "f(" << vals[0] << ") = " << fparser.Eval(vals)
                  << std::endl;
    }

    return 0;
}