PQOTD

[Marc Clifton]

Programming Quiz of the day. I just wrote this code (C#), which did something very unexpected. What was it that it unexpectedly did?

		bool more = ProcessFlyouts();
		more = more || ProcessCarrierAnimations();

How would you change it to "do the right thing?" Marc

[phil o]

Can you define 'right'?

[Flags]
public enum Bool {
True, False, ForSure, Maybe, ProbablyNot, Depends, NotDecidedYet, Undefined
}

private interface IStealth { }

[Marc Clifton]

You should be able to glean what the programmer intends to happen from the code. :) Marc

[Nish Nishant]

|

Regards, Nish

---

Blog: voidnish.wordpress.com Latest article: C++ 11 features in Visual C++ 2013 Preview

[Deflinek]

I'm not quite sure what was unexpected here. If you mean the ProcessCarrierAnimations() never gets called if (more == true) then it really was expected :) However changing || to | will make it called regardless of more's value.

-- "My software never has bugs. It just develops random features."

[phil o]

Maybe, if I could see the content of both methods that return a bool :) Otherwise, quite hard to detect a logic issue when the logic itself is not told.

[Flags]
public enum Bool {
True, False, ForSure, Maybe, ProbablyNot, Depends, NotDecidedYet, Undefined
}

private interface IStealth { }

[BobJanova]

It will run either ProcessFlyouts, or ProcessCarrierAnimations, or neither, and the variable will tell you if it successfully ran either. I would imagine you either want && or |.

[OriginalGriff]

I assume you meant it to do this:

bool more = ProcessFlyouts();
more = ProcessCarrierAnimations() || more;

:laugh: Would do the same in C and C++ as well.

Those who fail to learn history are doomed to repeat it. --- George Santayana (December 16, 1863 – September 26, 1952) Those who fail to clear history are doomed to explain it. --- OriginalGriff (February 24, 1959 – ∞)

[Kornfeld Eliyahu Peter]

I assume that you want to run the second method if first returns true, if that the case you have to switch the order

bool more = ProcessFlyouts();
more = ProcessCarrierAnimations() || more;

I'm not questioning your powers of observation; I'm merely remarking upon the paradox of asking a masked man who he is. (V)

[Marc Clifton]

Exactly. :)

[Marc Clifton]

deflinek wrote:

However changing || to | will make it called regardless of more's value.

Yup! Marc

[Marc Clifton]

Yup. | Marc

[Marc Clifton]

OriginalGriff wrote:

more = ProcessCarrierAnimations() || more;

Quite so. The bitwise | operator solves the problem too. Marc

[Marc Clifton]

Kornfeld Eliyahu Peter wrote:

you have to switch the order

Yes indeed. Or use the bitwise operator. Marc

[Rage]

MISRA[^] Rule 33 & 34:

The right hand operand of a || shall not contain side effects
The operands of a logical || shall be primary expressions

The example you gave is the very reason for the above two rules.

~RaGE();

I think words like 'destiny' are a way of trying to find order where none exists. - Christian Graus Entropy isn't what it used to.

[OriginalGriff]

Yes - but I don't like bitwise operators with bools...

Those who fail to learn history are doomed to repeat it. --- George Santayana (December 16, 1863 – September 26, 1952) Those who fail to clear history are doomed to explain it. --- OriginalGriff (February 24, 1959 – ∞)

[Rage]

Yep, but this is a workaround, not a best practice though.

~RaGE();

I think words like 'destiny' are a way of trying to find order where none exists. - Christian Graus Entropy isn't what it used to.

[Kornfeld Eliyahu Peter]

I do not like that change from C/C++...I mean the | and || changes... X|

I'm not questioning your powers of observation; I'm merely remarking upon the paradox of asking a masked man who he is. (V)

[BobJanova]

There's actually some nice concise uses of

var result = DoSomething() && DoSomethingThatDependsOnIt();
var result = DoSomething() || HandleFailureCase();

It's even better in languages where you can use non-boolean types with the boolean operators.

[Keith Barrow]

Though Nish's and OG's examples will work, I think it is symantically better to do this:

bool more = ProcessFlyouts();
bool foo = ProcessCarrierAnimations();
more = more || foo;

Less terse code (normally bad) - but explicit in calling ProcessCarrierAnimations.

PB 369,783 wrote:

I just find him very unlikeable, and I think the way he looks like a prettier version of his Mum is very disturbing.[^]