what does ":" mean in the declaration of a struct

Question

I can't understand the part of code “Point() : x(0), y(0) {}，Point(int a, int b) : x(a), y(b) {}”..

Especially about the question, ":" is used for what here?

thanks in advance!

 Definition for a point.
      struct Point {
          int x;
          int y;
          Point() : x(0), y(0) {}
          Point(int a, int b) : x(a), y(b) {}
      };

thank you, one mark, for a java programmer, the syntax to declare a constructor is really strange. — lhuang, Dec 15 '13 at 14:17

Gabriel · Answer 1 · 2013-12-15T14:17:32.460

1

it is used to begin an initializer list

x will be initalized with a and y with b in this example.

It is compulsory for const members of a class or a struct to use initialize it through an initializer list

edited Dec 15 '13 at 14:17

answered Dec 15 '13 at 14:11

Gabriel

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score 1 · Answer 2 · edited Dec 15 '13 at 14:17

1

Point() : x(0), y(0) {} <-- this is a constructor that creats a point at (0,0) coordonates. Point(int a, int b) : x(a), y(b) {} this is a constructor that creats a point at (a,b) coordonates. Where a and b are given as input by the user.

edited Dec 15 '13 at 14:17

t.niese

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answered Dec 15 '13 at 14:12

CiucaS

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score 0 · Answer 3 · answered Dec 15 '13 at 14:11

0

It's the start of an initialiser list for the members of the class/struct. You can use it call constructors of the class members, like you're doing there.

answered Dec 15 '13 at 14:11

splrs

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what does ":" mean in the declaration of a struct

3 Answers3