Need help with functions!

[ephraimr]

So I am trying to print the clark's tables for sin, cos tan etc and here is the code for sin :

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <math.h>
#include <iomanip>
using namespace std;


constexpr double pi = 3.14159;

double deg_to_rad(double deg){
     return deg * ( pi / 180 );
}

int main () {

     

     for (int i = 0; i < 90; ++i){

          cout << i << "  "; // to show which angle the row is

          for (double j = 0; j <= 0.9; j+= 0.1)
          {
               cout << setprecision(4) << sin( deg_to_rad(i + j) ) << " ";
          }

          cout << "\n";
     }

     cout << "\n";
     return 0;
}

The thing is, to print the tables of cos and tan, all I have to do is replace sin in line 26 with cos or tan. How do I change the above code (lines 20 to 30) to the function named clarketable that, if I call clarktable(cos) from the main function, it prints that table? That is, I want sin, cos or tan to be a parameter.

[minomic]

You can use an enumeration [1] and pass SIN, COS or TAN to your function. In your function you can have a 'switch' to print the correct table on the basis of what was passed as a parameter.

[1] http://en.cppreference.com/w/cpp/language/enum

[ephraimr]

In your function you can have a 'switch' to print the correct table on the basis of what was passed as a parameter.

Will not the function become thrice as large if I use the switch? All I want is to change one thing in line 26. Is there a way to search and replace just that in the function? Something like a 'define'? I am new so forgive me for asking stupid questions.

[minomic]

No, the function will become only slightly larger. What I was thinking of is something like this:

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <math.h>
#include <iomanip>
using namespace std;


const double pi = 3.14159;

double deg_to_rad(double deg){
     return deg * ( pi / 180 );
}

enum FUNCTION {SIN, COS, TAN};

void table(FUNCTION f) {
     for (int i = 0; i < 90; ++i){

          cout << i << "  "; // to show which angle the row is

          for (double j = 0; j <= 0.9; j+= 0.1)
          {
               switch(f) {
                    case SIN:
                    cout << setprecision(4) << sin( deg_to_rad(i + j) ) << " ";
                    break;

                    case COS:
                    cout << setprecision(4) << cos( deg_to_rad(i + j) ) << " ";
                    break;

                    case TAN:
                    cout << setprecision(4) << tan( deg_to_rad(i + j) ) << " ";
                    break;
               }
          }

          cout << "\n";
     }
}

int main () {

     table(COS);     

     cout << "\n";
     return 0;
}

[MiiNiPaa]

there a way to search and replace just that in the function?

You can pass function as a function parameter. And you can use switch to pass correct function as parameter.

Example:

#include <iostream>
#include <iomanip>
#include <functional>
#include <cmath>

constexpr double pi = 3.14159265358;

double deg_to_rad(double deg)
{
    return deg * ( pi / 180 );
}

void print_table_impl(std::function<double(double)> op)
{
    for (int i = 0; i < 90; ++i) {
        std::cout << std::setw(2) << i;
        for (int j = 0; j < 10; ++j)
            std::cout << ' ' << std::setw(7) << op( deg_to_rad(i + j/10.) );
        std::cout << '\n';
    }
}

enum func { SIN, COS, TAN };

void print_table(func op)
{
    switch(op) {
        case SIN: print_table_impl(sin); break;
        case COS: print_table_impl(cos); break;
        case TAN: print_table_impl(tan); break;
    }
}

int main ()
{
    std::cout.flags(std::ios::fixed);
    std::cout.precision(4);
    std::cout << "Which table do you need?\n\t1: Sin\n\t2: Cos\n\t3: Tan\n";
    int choice;
    std::cin >> choice;
    switch(choice) {
        case 1: print_table(SIN); break;
        case 2: print_table(COS); break;
        case 3: print_table(TAN); break;
    }
}

Of cource you can ditch enum and pass integers directly to print_table.
Edit: fixed missing breaks
Edit 2: Beautified output.

[ephraimr]

minomic, Thank you so much :)
MiiNiPa, Thank you! That cleared it up! Never knew there was something like that!

[MiiNiPaa]

For underlying mechanism you can read information on function pointers (they are slightly more complex to use, but it is what std::function uses internally):
http://www.learncpp.com/cpp-tutorial/78-function-pointers/