FAQ: Functions: Scope & Flexibility - Review

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#1

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This community-built FAQ covers the “Review” exercise from the lesson “Functions: Scope & Flexibility”.

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#2

I’m trying to build a function that does the same thing as in the example ( 7/ 9 ).

add_together()

which takes two arguments and, if they’re numbers, adds them, and if they’re strings/characters, concatenates them.

Since i’m using a template, i don’t have any relevant fns.cpp, but my fns.hpp is as follows:

template
T add_together(T input1, T input2){
return input1 + input2;
}

I know that strings can be concatenated using the “+” operator, and yet when i try to run my test main(), as follows:

#include <iostream>
#include “fns.hpp”
#include <string>
int main() {
std::cout << add_together(1,2) << “\n”;
std::cout << add_together(“A”, “B”) << “\n”;
}

I get the following:
error: invalid operands of types 'constant char*' and 'constant char*' to binary 'operator+'
After some googling i see that constant characters cannot be added together, but a constant character can be added to a string, but if, within my main(), i specify as follows:

std::cout << add_together(std::string “A”, “B”) << “\n”;

then the error changes to:
error: expected primary-expression before string constant
std::cout << combine(std::string "A", "B" << "\n";

and i have no clue what that means. Any ideas?

1 Like
#4

I decided to challenge myself by using one function inside of another function. It took me a lot of debugging to get it straight, but it was worth it! My idea was to create a program which calculates kinetic energy from an object’s mass, displacement (that’s distance in a particular direction), and the time taken to make the movement. Here is the main.cpp file of my code:

#include <iostream>
#include "fns.hpp"

int main() {
  std::cout << kinetic_energy(80, 25, 16) << "\n";
}

//KE = 0.5 * 80 * ((25 / 16) * (25 / 16))
//KE = 97.6562 Joules

Here is the fns.hpp file of my code:

double kinetic_energy(double mass, double displacement, double time);
double average_velocity(double displacement, double time);

Here is the fns.cpp file of my code:

double average_velocity(double displacement, double time) {
  return displacement / time;
}
double kinetic_energy(double mass, double displacement, double time) {
  return 0.5 * mass * (average_velocity(displacement, time) * average_velocity(displacement, time));
}

Thank you, Codecademy for the fact that I was able to code this! Keep up the good work!