c++ Getting wrong calculation from a function - c++

Question

This is my code of a function. In main i check if temperature is in kelvin or fahrenheit. When I get temp_enota = 'F' from main ( I do because I checked with debugging), and temp = 116 for some reason function returns 0 when it should be around 46. Any ideas why? It works fine for kelvins.
float pretvorbaTemp(char temp_enota, float temp) {
if (temp_enota == 'K') {
temp = temp - 273.15;
}
else if (temp_enota == 'F') {
temp = (temp - 32) * (5 / 9);
}
return temp;
}
calling from main function
if (temp >= 283 && temp <= 323) {
temp_enota = 'K';
zacasna = 1;
cout << "Vnesena temperatura je v K, kar je enako "<<pretvorbaTemp(temp_enota, temp)<<" C" << endl;
}
else if (temp <= 122 && temp >= 50) {
temp_enota = 'F';
zacasna = 1;
cout << "Vnesena temperatura je v F, kar je enako "<<pretvorbaTemp(temp_enota, temp)<<" C" << endl;
}
else if (temp >= -10 && temp < 50) {
temp_enota = 'C';
zacasna = 1;
cout << "Vnesena temperatura je v C" << endl;
}
else {
zacasna = 0;
zacasna2 = 1;
}

Answer 1

The reason you get 0 is because the expression
5/9
will evaluate to 0 as these are two integer values, thus the compiler generates the code to do an integer division.
Just change to
5./9
to force floating point.

Answer 2

Do this:
float pretvorbaTemp(char temp_enota, float temp) {
if (temp_enota == 'K') {
temp = temp - 273.15;
}
else if (temp_enota == 'F') {
temp = (temp - 32.0) * (5.0 / 9.0);
}
return temp;
}
Here temp = (temp - 32) * (5 / 9); the values are int. You need to use them as float.