Function rb_sys::macros::FIXNUM_P

pub fn FIXNUM_P<T: Into<VALUE>>(obj: T) -> bool

Checks if the given object is a so-called Fixnum.

@param[in] obj An arbitrary ruby object. @retval true obj is a Fixnum. @retval false Anything else. @note Fixnum was a thing in the 20th century, but it is rather an implementation detail today.