center(*args)
public
If integer is greater than the length of str, returns a new String of
length integer with str
centered and padded with padstr; otherwise, returns str.
"hello".center(4)
"hello".center(20)
"hello".center(20, '123')
static VALUE
rb_str_center(int argc, VALUE *argv, VALUE str)
{
return rb_str_justify(argc, argv, str, 'c');
}