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question about c language

 
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Marc
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question about c language
PostPosted: Thu Jul 12, 2007 8:16 am     Reply with quote

I need to simplify the code

if (va>=817) in=0;
else if ((va>=750) && (va>760)) in=3;
else if ((va>=730) && (va>740)) in=4;
else if ((va>=710) && (va>718)) in=5;
else if ((va>=685) && (va>695)) in=6;
else if ((va>=665) && (va>675)) in=7;
else if ((va>=645) && (va>655)) in=8;
else...

How can I use switch...case in this situation?

Thank You
SherpaDoug



Joined: 07 Sep 2003
Posts: 1639
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PostPosted: Thu Jul 12, 2007 9:38 am     Reply with quote

Beware switch statements usually take an int. 817 doesn't fit in a CCS int. I don't know if CCS lets you use something larger than an int.
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inservi



Joined: 13 May 2007
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PostPosted: Fri Jul 13, 2007 1:34 pm     Reply with quote

Hello Marc,

Is that real code used in your program ?

dro.
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libor



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PostPosted: Sun Jul 15, 2007 3:21 am     Reply with quote

You made a typo I think, the second > would have been < .

To the point: I would use a lookup table and make the quantization in a loop rather then to have that many if elseif-s.
declare a const array with the range values, and find the range in a loop the value fits in. This makes the code more maintanable also.
ckielstra



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PostPosted: Sun Jul 15, 2007 5:55 am     Reply with quote

Another problem with the given example code is that there are gaps in between the tested ranges. For example 740 - 750 is not handled while I suspect that's not what the programmer intended.

If there are indeed no gaps intended the test can be simplified as:
Code:
if (va>=817) in=0;
else if (va>=750) in=3;
else if (va>=730) in=4;
else if (va>=710) in=5;
else if (va>=685) in=6;
else if (va>=665) in=7;
else if (va>=645) in=8;
else...


Quote:
To the point: I would use a lookup table and make the quantization in a loop rather then to have that many if elseif-s.
declare a const array with the range values, and find the range in a loop the value fits in. This makes the code more maintanable also.
A very nice suggestion. The if-else construction will be more memory efficient when only a few ranges have to be detected, lets say up to a maximum of 10 - 15 tests.
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