How to understand "(x >= 0 ? x : -x)" ?

Projects Programming
1

greets,

I was reading a tutorial on #define and const and there is an example there:

#define AbsoluteValue(x) (x >= 0 ? x : -x)

I don't understand how (x >= 0 ? x : -x) works.

can some explain it?

thanks!

2

It's a compact IF/ELSE statement.
if( x >= 0)
{
//if true
return x;
}
else
{
// otherwise false
return -x; // x *= -1
}

3

It's a shorthand way of saying

if(x>=0)
 x=x;
else
  x=x*-1;

You can use this in many places the common form is (condition)? valueIfTrue:valueIfFalse;

some more examples

Serial.print((id==7)? "hello Brian":"who are you?");
 
 x=(scale=='F')? temperature * 5/9 : temperature;
4

There are many uses for it,

If the true or false parts are an lvalue expression, so is the result:

( val ? PORTA : PORTB ) &= ~_BV( 2 );

For more reading, I wrote an article on the conditional operator.