Numeric literals can be type annotated by adding the type as a suffix. As an example,
to specify that the literal 42 should have the type i32, write 42i32.
The type of unsuffixed numeric literals will depend on how they are used. If no
constraint exists, the compiler will use i32 for integers, and f64 for
floating-point numbers.
There are some concepts used in the previous code that haven't been explained
yet, here's a brief explanation for the impatient readers:
std::mem::size_of_val is a function, but called with its full path. Code
can be split in logical units called modules. In this case, the
size_of_val function is defined in the mem module, and the mem module
is defined in the stdcrate. For more details, see
modules and crates.