How to check the given point is in selected line or not?

Question

Say I have a line, and then I am randomly given a point. I want to check whether the given point is on the line or not? I am using autocad with vba

Answer 1

Here's a simple VBA function to check if the point (x, y) is on a line with slope m and y-intercept b:

Function PointOnLine(x As Double, y As Double, m As Double, b As Double) As Boolean

Dim Difference As Double

Difference = m * x + b - y

If Abs(Difference) < 0.0000000001 Then

PointOnLine = True

Else

PointOnLine = False

End If

End Function

Ideally, you want the value of Difference in the function to be 0, but in practice, you may get rounding errors, which is why I put in Abs(Difference) < 0.0000000001, which is 1.0E-10. You may want to make this number larger or smaller, depending on the accuracy of the calculations of your values of x, y, m, and b.