What is the meaning of a dot (.) after an integer in c?

问题

I would like to know if anybody knew what a . after an integer in C means.

i have this piece of code i want to convert and that is the only thing i am not sure of what it does.

if (y>=0.) what does the . here do?

full code:

double angleOf(double x, double y) {

  double  dist=sqrt(x*x+y*y) ;

  if (y>=0.) return acos( x/dist);
  else       return acos(-x/dist)+.5*CIRCLE_RADIANS; }

回答1:

It's same as 0.0, it will treat it as double instead of an integer, so you don't need to cast it.

回答2:

The trailing dot makes the literal a floating point (double) literal, instead of an integer one.

来源：https://stackoverflow.com/questions/14626715/what-is-the-meaning-of-a-dot-after-an-integer-in-c