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Simple syntax question

Posted on 2004-08-02
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Last Modified: 2010-04-01
Please describe what this does:

byIndex = (m_csBitmaps[2].hBitmap == NULL ? 0 : 2);

Is it some kind of "if then else" shorthand?
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Question by:PMH4514
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5 Comments
 
LVL 55

Expert Comment

by:Jaime Olivares
ID: 11697780
Yes, it is some kind of if...then...else

value = condition ? return_for_true : return_for_false;

It is a common operator in many languages.
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Expert Comment

by:grg99
ID: 11698375
It's a bit of if/the/else shorthand for expressions.  A bit cryptic.

In this case it says:  if the .hBitMap is NULL, this side of the equals sign has a "0", otherwise it has a "2".

In other less cryptic (altho dead) languiages like Algol, youd say the same thing in a much less head-scratching form:


byIndex :=  if m_csBitmaps[2].hBitmap = NULL  then 0  else 2;

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LVL 55

Accepted Solution

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Jaime Olivares earned 25 total points
ID: 11698445
Equivalent C expression:

if (m_csBitmaps[2].hBitmap == NULL)
      byIndex = 0;
else
      byIndex = 2;

Shorter expression:

if (!m_csBitmaps[2].hBitmap)
      byIndex = 0;
else
      byIndex = 2;
0
 

Author Comment

by:PMH4514
ID: 11698517
thanks Jamie.. I was pretty sure of that.. I've seen it before, I tend to write more verbose code.. that's going to change now that I'm doing lower level stuff.. I wonder if the shorthand is any faster once compiled? (if so it's probably not even perceptable even with timer scripts)

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LVL 55

Expert Comment

by:Jaime Olivares
ID: 11698541
> I wonder if the shorthand is any faster once compiled?
That is a compiler-dependent feature, if you are very interested, you have to some a performance test by yourself.
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