Can't understand logic of perimeters

[MrMeatBoy]

Hi, I am student currently studying computer games development. I am having trouble coming to terms with what parameters are really used for.
A lot of the time when I am learning I have to completely understand why something is used otherwise I just refuse to use it myself, especially with programming. If anyone could give me a good example or reason why I would want to use perimeters in my functions, I would greatly appreciate it!

Thanks

Ross

[Duthomhas]

Am I to assume that you mean "parameters" every time you write "perimeters"? Because they are two totally different things...

Why is the idea of a parameter so difficult?

    Person A: "Hey, I'm making sandwiches. What do you want?"

    Person B: "I don't believe in parameters. I'll just take the two slices of bread."


    Plumber: "There you go Mrs Johnson. Your bathroom has been entirely replaced. That'll be $7,000."

    Mrs Johnson: "But... I only had a leaky faucet."

    Plumber: "Sorry. I don't use parameters. It's all or nothing."


I'm not trying to be mean -- just to illustrate. A parameter is a modifier -- it tells us specifics about something.

    I want a peanut butter and jam sandwich.

    I want a list of the first twelve Fibonacci numbers.

It is through parameters that the functionality of our code gains variability.


Now, whether you pass them as argument or just maintain a giant list of global structures doesn't really matter -- they are still parameters to your code. (But you really should try to localize stuff.)

Parameterizing functions is a basic computational principle that lets you reuse code to operate on different data.

Here's a (very simple) example:

#include <iostream>
#include <vector>
using namespace std;

void print( const string& name, vector <int> xs )
{
  cout << name << ": ";
  for (int x : xs)
    cout << x << " ";
  cout << endl;
}

int main()
{
  vector <int> primes = {{2, 3, 5, 7, 11, 13, 17, 19}};
  vector <int> fibonaccis = {{1, 1, 2, 3, 5, 8, 13, 21, 34, 55}};

  print( "Some primes", primes );
  print( "Fibonacci numbers", fibonaccis );
}

Conveniently, I used the same function to print two totally different lists of numbers!

Hope this helps.

[keskiverto]

Lets take a math equation:

y = 7*x + 42

When you replace the x with a number of your choosing, the equation can evaluate the corresponding y.

Lets turn that into a function:

int foo( int x )
{
  return 7*x + 42;
}

Now you can call in your code the function foo, but you have to give a value of x as parameter, and the function will return the corresponding value of y.

The function has code for how to do something, but the parameters deliver what to do it for.

[MrMeatBoy]

Hey peeps, thanks a lot for your quick responses. Yeah I did mean "parameter", for some reason my browser told me it was an incorrect spelling when I first typed that, now I feel like a donk haha.

Thanks for the help, I honestly haven't looked at the logic in this way.

Ross

[Duthomhas]

Autocorrect drives me bonkers -- and I still can't figure out how to turn it off.

I meant to spell what I spelt
Dumb autocorrect
Thinks it's smarter than I am