DPGEGDX Ray Cast

public static float dist(float x1, float y1, float x2, float y2) {
    return (float) Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
}

public static float getRayCast(float p0_x, float p0_y, float p1_x, float p1_y, float p2_x, float p2_y, float p3_x, float p3_y) {
    float s1_x, s1_y, s2_x, s2_y;
    s1_x = p1_x - p0_x;
    s1_y = p1_y - p0_y;
    s2_x = p3_x - p2_x;
    s2_y = p3_y - p2_y;

    float s, t;
    s = (-s1_y * (p0_x - p2_x) + s1_x * (p0_y - p2_y)) / (-s2_x * s1_y + s1_x * s2_y);
    t = (s2_x * (p0_y - p2_y) - s2_y * (p0_x - p2_x)) / (-s2_x * s1_y + s1_x * s2_y);

    if (s >= 0 && s <= 1 && t >= 0 && t <= 1) {
        // Collision detected
        float x = p0_x + (t * s1_x);
        float y = p0_y + (t * s1_y);

        return dist(p0_x, p0_y, x, y);
    }

    return -1; // No collision
}

Could you describe the arguments a little bit more clear?

public static float dist(float LineStartX, float LineStartY, float LineEndX, float LineEndY)
{
return (float) Math.sqrt((LineEndX - LineStartX) * (LineEndX - LineStartX) + (LineEndY - LineStartY) * (LineEndY - LineStartY));
}

public static float getRayCast(float RayStartX, float RayStartY, float RayCosineDist, float RaySineDist, float LineStartX, float LineStartY, float LineEndX, float LineEndY) {
float RayEndX, RayEndY, LineXDiff, LineYDiff;
RayEndX = RayCosineDist - RayStartX;
RayEndY = RaySineDist - RayStartY;
LineXDiff = LineEndX - LineStartX;
LineYDiff = LineEndY - LineStartY;

float s, t;
s = (-RayEndY * (RayStartX - LineStartX) + RayEndX * (RayStartY - LineStartY)) / (-LineXDiff * RayEndY + RayEndX * LineYDiff);
t = (LineXDiff * (RayStartY - LineStartY) - LineYDiff * (RayStartX - LineStartX)) / (-LineXDiff * RayEndY + RayEndX * LineYDiff);

if (s >= 0 && s <= 1 && t >= 0 && t <= 1) {
    // Collision detected
    float x = RayStartX + (t * RayEndX);
    float y = RayStartY + (t * RayEndY);

    return dist(RayStartX, RayStartY, x, y);
}

return -1; // No collision

}