Regarding abs() and labs()

Hello all

Just took a look at abs() and can not understand why it seem so overcomplicated. Why not just:

#define abs(x) ((x) < 0) ? -(x) : (x))

and skip labs() (not used anyway)
+ it gives a warning with -W if x is of a unsigned type ("condition is always false" or similar).
But remember to use %u when printing an unsigned, took me a while before I understood how an unsigned could contain a "negative" value :)

Quoted 5 lines · On Sat, 03 Feb 2007 02:13:44 +0100 Richard Knutsson wrote:

Hello all

Just took a look at abs() and can not understand why it seem so overcomplicated. Why not just:

Quoted 2 lines

#define abs(x) ((x) < 0) ? -(x) : (x))

It's almost that simple. It just adds a local __x so that 'x' won't be evaluated multiple times as it would in the simpler version. Multiple evaluations (of an expression) (that could have side effects) would take more CPU horsepower and could have bad side effects as well.

Quoted 11 lines · Randy Dunlap

Quoted 7 lines · On Sat, 03 Feb 2007 02:13:44 +0100 Richard Knutsson wrote:

Hello all

Just took a look at abs() and can not understand why it seem so overcomplicated. Why not just:

#define abs(x) ((x) < 0) ? -(x) : (x))

Quoted 6 lines

It's almost that simple. It just adds a local __x so that 'x' won't be evaluated multiple times as it would in the simpler version. Multiple evaluations (of an expression) (that could have side effects) would take more CPU horsepower and could have bad side effects as well.

You mean if x is ex a + b? In such case; why not use typeof instead of int?

What kind of side-effects are you talking about?

Quoted 21 lines · On Sat, 03 Feb 2007 03:22:29 +0100 Richard Knutsson wrote:

Quoted 19 lines · Randy Dunlap

Quoted 8 lines · On Sat, 03 Feb 2007 02:13:44 +0100 Richard Knutsson wrote:

Hello all

Just took a look at abs() and can not understand why it seem so overcomplicated. Why not just:

#define abs(x) ((x) < 0) ? -(x) : (x))

It's almost that simple. It just adds a local __x so that 'x' won't be evaluated multiple times as it would in the simpler version. Multiple evaluations (of an expression) (that could have side effects) would take more CPU horsepower and could have bad side effects as well.

Quoted 2 lines

You mean if x is ex a + b? In such case; why not use typeof instead of int?

I suppose that would make sense if we have a need for abs(various types), but until we do, just using: int __x; is good enough.

Quoted 2 lines

What kind of side-effects are you talking about?

The usual kind that affect computer software. E.g.:

	a = abs(var1++);