src/libstd/os/raw/double.md

   1 Equivalent to C's `double` type.
   2
   3 This type will almost always be [`f64`], which is guaranteed to be an [IEEE-754 double-precision float] in Rust. That said, the standard technically only guarantees that it be a floating-point number with at least the precision of a [`float`], and it may be `f32` or something entirely different from the IEEE-754 standard.
   4
   5 [IEEE-754 double-precision float]: https://en.wikipedia.org/wiki/IEEE_754
   6 [`float`]: type.c_float.html
   7 [`f64`]: ../../primitive.f64.html