Thread: Constructor excercise

This excercise is from C++ primer 5th edition.

I have not understood everything about constructors, mainly about how they function.

Work prior to the excercise was creating a class called screen with some specifications.
This is the class:

Code:

class screen{
public:
    using pos = string::size_type;
    screen() = default;
private:
    pos height = 0;
    pos width = 0;
    pos cursor = 0;
    string contents;
};

The excercise goes as follows:
Excercise 7.24: Give your Screen class three constructors: a defaultconstructor; a constructor that takes values for height and width and initializes the contents to hold the given number of blanks; and a constructor that takes values for height, width, and a character to use as the contents of the screen.

Giving the screen a default constructor was easy. The next part is probably easy aswell, I just dont understand what they mean when they say "and initalize the contents to hold the given number of blanks" and something in the 3rd part when they say "character to use as the contents of the screen". If anyone of you guys could explain it to me, it would make my day!

Edit: Think I have made a breakthrough... Would the constructor for the second part look like this:

screen(pos ht, pos wd) : contents(ht*wd) {}

or something?

Originally Posted by Iceboxes

I just dont understand what they mean when they say "and initalize the contents to hold the given number of blanks"

In other words, you need to make use of the values for height and width to call the appropriate string constructor to initialise the member variable named contents with blanks (presumably a "blank" is a space character).

Originally Posted by Iceboxes

something in the 3rd part when they say "character to use as the contents of the screen"

Instead of initialising contents with blanks, you would initialise it with the given character.

Do I set "Contents" equal to something in the constructor, or am I supposed to do that when I declare it?

Are these constructers what the book is asking for?

Code:

screen(pos ht, pos wd) : height(ht), width(wd), contents(ht*wd, ' ')    
screen(pos ht, pos wd, char) : height(ht), width(wd), contents(ht*wd, c)

Originally Posted by Iceboxes

Are these constructers what the book is asking for?

I think so (since you only have one string, rather than a rectangular array of strings), except that you forgot to name the char parameter c and include the constructor body in both cases.

Originally Posted by laserlight

forgot to name the char parameter c and include the constructor body in both cases.

Was writing on my phone, so some details was easily forgotten >.>

Thanks to everyone that helped me, you guys are awesome!!!!!