finding if a number is in range

[fguihen]

ok for a simple example, lets say i have two numbers, x=10, y=2.

i want to check if z=5 is between theese ranges.

 

if(x>z && y < z)
{
//z is in the range
}

now this will fail if x is smaller than y, even though z would still be in the range.

 

i have to do this with points. i have a point. i have to check if this point is between 4 other points. before anyone starts, im not asking to find if two lines intersect, i can do that already. my problem is that my algorithm checks if infinite lines intersect, and i have to then check if the intersection point found by my program is within the range of both line segments. as you can see this would lead to quite a large if statement. also, as you can see if the line is sloped funny ( x is before y) then the algorithm wont detect a collision. i tried swapping points but its hard to call if one line is bigger or smaller than another. anyone got any ideas?

[PlausiblyDamp]

would the following not work?

if((x>z && y < z) || (y >z && x{

}

[twistedm1nd]

would this work ?

 

if(Math.Abs(x-y)>z)

[fguihen]

what does the math.abs function do??

[Mike_R]

what does the math.abs function do??

Math.Abs() returns the "absolute value" of the input. In short, all negative numbers beccome positive. Some examples:

 

Abs(-5) = 5

Abs(3) = 3

Abs(0) = 0

Abs(-11) = 11

 

However that equation does not work. For example, 15 is between 10 and 20. So z= 15, x = 10, y = 20 should return True. But f(Math.Abs(x-y)>z) would retun False.

 

Use PlausiblyDamp's equation instead:

 

if((x>z && y < z) || (y >z && x<z))

 

:)

Edited February 16, 2005 by Mike_R

[Iceplug]

Abs() makes a number positive.

 

To check if a number is in a range (including the boundaries), go for Plauisbly's suggestion, or

if ( x > y) {
 if (x>z && y<z) {
 }
} else {
 if (y>z && x<z) {
 }
}

:)

[Nerseus]

Maybe it's just me, but I like to read the code like I think about it. I'd put z on the left of each comparison, like so: "if (z>x && z<y)"

 

Meaning, I want to compare z to something, not compare x and y to something. In my head I say "If z is greater than x and less than y" so it's nicer to read the code that way.

 

Or even better, refactor to a function:

private bool Between(int compareNumber, int boundA, int boundB)
{
   ....
}
if(Between(z, x, y))
{
   ....
}

 

Maybe not the best names (Between, boundA, etc.), but still... make the code readable. Then the swapping of x and y can be hidden in the function to handle when boundA > boundB or when boundA < boundB.

 

-ner

[IngisKahn]

Yet another way:

 

if (z > Max(x, y) && z < Min(x, y))