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From: Alexey Ruzin <[e-mail]>
Newsgroups: comp.lang.c++
Subject: Re: Constructor and enum Question...
Date: Tue, 16 Apr 1996 21:02:58 +0400
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cwu wrote:
>
> Recently I am studying C++ and have a difficulty to understand
> "constructor" and "enum".  I am very appreciated any comments.

Hi, excuse me for my Engilsh.

As for 'enum':

In short, it looks like set of defines, which declare 'int' constants.
These defines are grouped in type, but you don't need use it mnemonic
names always. Example:

...
enum {a,b,c} f;
...

this is equal:

...
#define a 0
#define b 1
#define c 2
int f; /* f may be 0,1,2; Hmm... i never tried to initialize with
          another values... It's interesting... ??? */
...

Of course, if it was no difference between 'enum' and 'defines' there
would no 'enums' and 'defines' together. But at the beginning of
undestanding you may believe it.

As for 'constructor':

Again in short, It is function first called when object is initialized.
In practice it is function is served to DO THIS JOB (initialization).
Imagine a child, each child has a child and he knows her
with birth. Lets make two classes 'Child' & 'Mother':

class Mother
{
...
};

class Child
{
  Mother mom;
...
public:
  Child( Mother the_mom ) { mom = the_mom; }
};

...

main()
{
...
  Mother a_mother;
  Child a_child( a_mother );
...
}

As we see, each child at moment of birth is initialized with value
of his monther. Who does this work -> 'constructor'. Another way
call some functions after birth to say what is mother of a child,
but constructor works perfectly. In addition, there are some
cases where no way to misuse (don't use) constructor (when
you use references: int &a=b; :this is one way to initialize variable
-> use constructor).

I hope it helps... Good luck.

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