Question

when I use:

if( a>=0 && a<100 && b>=0 && b<200 )

everything works fine but if I use:

if( 0<=a<100 && 0<=b<200 )

my program crashes. a and b = floats. Can somebody please tell me what’s the difference?

Answer 1

0<=a<100 is actually (0<=a)<100. Since (0<=a) is a boolean, its value is always either 0 or 1 (true or false), therefore the expression becomes 0<100 (or 1<100), which is always true.

Since you are sort-of indexing an array with a and b, the wrong bounds check leads to, well, an out-of-bounds access, which crashes your application.