Circle line-segment collision detection algorithm?

Question

I have a line from A to B and a circle positioned at C with the radius R.

What is a good alg

Answer 1

Here is good solution in JavaScript (with all required mathematics and live illustration) https://bl.ocks.org/milkbread/11000965

Though is_on function in that solution needs modifications:

function is_on(a, b, c) {
    return Math.abs(distance(a,c) + distance(c,b) - distance(a,b))<0.000001;
}