Tutorial Functions and classes explained

_Seb1 · January 5, 2019

So in this information thread I will explain what a Class is and what they are used for. Before I can explain what a Class is I must explain Functions and their usage.

The idea behind Functions that the code should be executed multiple times, so it gets outsorced to a Function. Such Functions can be called randomly in the program and if that happens all the Instructions in the function will be executed. The usage of Functions are not only to prevent code doubles. They can be appointed very flexibal

- While calling the Function up, your able to send Data into it.

- After the Function has ended you can return Data to its calling place.

as example we will take an easy math function:

f(x) = x²

this function can be called with different Parametres and always computes the square of it. When it gets called up with the parametre 2 it delivers 4 as result.

They are able to work more than a math function though:

- the quantity of the parametres aren‘t limited. You can use many parametres.

- The Datatypes(Int, Float/Double etc other thread) are free choosable so you can use strings or booleans too.

- You can return values to its access point.

How is a Function made?

Name

Parametres

Return type

Functionstrunk

Must not be like this, but as C++ is very strict about that, you will need to write all that.

Example for a function:

Return Type Functionname(List_of_Parametres)

{(start of the functionstrunk aka Codeblock)

Instruction1;

Instruction2;

....

}

If a Function should not return Data the special return type void is used.

The list of parametres is a seperated list of Datatype-Name-Pairs.(int alpha, string beta)

The return instrction

The return instruction ends the function and gives the data back to its calling place. example the function f(x) = x²:

int f(int x)

{

int y;

y = x * x;

return y;

}

That above is Pseudocode, you can realize it like that but there are parts missing(like defining x).

It is possible to use more than one return instruction. So as example:

int max(int x, int y)

{

if (x > y)

return x;

return y;

}

It checks if x is bigger than y if thats true it gives back the data to its calling place and ends the function. If it is not true it returns y to the calling place and the function ends here.

Failures in the Function code

int max_failmao(int x, int y)

{

if (x > y)

return y;

}

👆wrong because there isnt a return instruction defined for x.

void failures

Void return type: Doesnt return values.

So

void Joka( )

{

return 5;

}

👆failure

You can still use a return instruction in a void function to end it prematurely.

void WithJoka(int x)

{

if (x > 5)

return;

}

Recursions.

Now because this is not used very often due to its high amount of storage eat, you won‘t face it very often.

int Recursionexample()

{

return( ) + 1

}

would always call itself up again and add 1 to its parametres. This endlessrecursion would cause a crash of the program. Recursions are a very elegant way to solve problems but it takes muh storage due to its recalls.

Classes

What is a „Class“?

A class is an own datatype you can manage after your favor. In those classes objects(so called instances) are saved. So for the class „Human“ Seb, Tronald Dump etc. can be chosen as instances. Characteristic for classes is that all instances have the same skills(So called attributes: howtall; weight). Every Instance in a class can perform actions: Like baking a cake(humans).

the skills of each instance can vary(not always the same weight).

You can simulate an own similar world with those classes.

How do you realize it in code?

3 parts:

The name

The skills

The actions

So in C++ a class is made like this:

(easy class)

class ClassnameJokaGay

{

..... Skills and actions .....

}

Actions are realized by functions in this actions are called methods of a class if you made it with functions. In the class you can access the skills(attributes)

Classes always have constructures, those methods are used to make new classinstances. Well now we know how to build a class, but what about a Constructor?

A Constructor is made like a function, having the same name like the class and without giving the return type.

ex.:

class score

{

....

score( )

{

quantitygoalsteam1 = 0;

quantitygoalsteam2 = 0;

}

So because they are playing and they could shoot some goals we need methods to realize that class.

so ex.: