Point distance

Explanation
This function uses the Pythagorean theorem to calculate the distance between point (x1,y1) and point (x2,y2). How this function could look in pure GML:

dist=sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1))

Examples
This code creates a bullet that travels in the direction of obj_enemy if the distance to that object is smaller then 200 pixels. var iii; if point_distance(x,y,obj_enemy.x,obj_enemy.y)<200 { iii=instance_create(x,y,obj_bullet); iii.direction=point_direction(x,y,obj_enemy.x,obj_enemy.y); }