Comments on: 8.5 — Constructors

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Learn C++ - » 8.6 — Destructors — Fri, 08 Aug 2008 17:48:33 +0000

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By: Learn C++ - » 8.4 — Access functions and encapsulation

Learn C++ - » 8.4 — Access functions and encapsulation — Mon, 05 May 2008 01:55:31 +0000

[...] 2007 Prev/Next Posts « 8.3 — Public vs private access specifiers | Home | 8.5 — Constructors » Tuesday, September 4th, 2007 at 2:21 [...]

By: Tom

Tom — Fri, 28 Mar 2008 04:37:42 +0000

Typo:

“Date cToday(9, 5, 2007); // cDate is initialized to Sept 5th, 2007 ”

Should be:

“Date cToday(9, 5, 2007); // cToday is initialized to Sept 5th, 2007 ”

[ Fixed. Thanks! -Alex ]

By: Alex

Alex — Tue, 15 Jan 2008 00:52:14 +0000

In a class, you can’t initialize values on the line they are declared like that. Non-static class values should be initialized in the constructor body or initialization list. Static class values should be initialized in the body of the class definition.

I am not sure what the reasoning is for this design decision. I presume simply because the constructor is the function that is supposed to initialize your values. If you were allowed to do default values this way, then many variables would be initialized twice (once in the declaration, once in the constructor). This would be both inefficient and confusing.

By: Renu

Renu — Tue, 15 Jan 2008 00:22:45 +0000

class Fraction
{
private:
int m_nNumerator =10;
int m_nDenominator=20;

public:
Fraction() // default constructor …….

I tried initialising m_nNumerator =10 and int m_nDenominator=20

got this error ” only static const can be initialised ….”

Then I tried

private:
static const int m_nValue=22;
int m_nNumerator ;
int m_nDenominator;
It worked.

Could you please explain? Does that mean private member variable cannot be initialised when they are declared? If so ,is there any specific reason for that?

Thanks,
Renu

By: Renu

Renu — Tue, 15 Jan 2008 00:17:49 +0000

double GetFraction() { return static_cast(m_nNumerator)/nDenominator; }

“m_nNumerator)/nDenominator” should be “m_nNumerator)/m_nDenominator ”
at all three places in the tutorial.

Thanks,
Renu

By: Alex

Alex — Sat, 12 Jan 2008 19:09:54 +0000

I talk about assert in section 7.12. In short, it’s a way to test whether an expression is true, and if not, stop the program at that point.

By: Abhishek

Abhishek — Sat, 12 Jan 2008 08:16:00 +0000

what’s assert() ?

By: Alex

Alex — Sat, 29 Dec 2007 01:32:11 +0000

Great point! I updated the example. Dividing by 0 will definitely crash the program.

By: Cody

Cody — Sat, 29 Dec 2007 00:42:56 +0000

As a review you could include protecting m_nDenominator from invalid assumptions by making sure it is not set to 0. This is because, if I remember correctly, dividing anything by zero will probably cause the program to crash so the function GetFraction() would most likely crash the program if the denominator is 0.