Variable assignment

Code	Description
`let n = 5;`	Assign the value, `5`, to `n`. The type of `n` is deduced.
`let n : i32 = 5;`	Assign the value, `5`, to `n`. `n` is an `i32`.
`let n;`	Create a placeholder variable named `n`. We may assign to it (once) later.
`let mut n = 5;`	Assign the value, `5`, to `n`. `n` is mutable and may be changed later.
`let n = i == 5;`	Assign the result of the expression, `i==5` (true or false), to `n`. The type of `n` is deduced.
`x = y;`.	Move `y`’s value into `x` (you can no longer use `y`), unless `y` is a copyable type. If its type implements `[derive(Copy)]`, a copy is made and `y` remains usable.

Structures

Code	Description
`struct S { x:i32 }`	Create a structure containing a field named `x` of type `i32`. Access as `s.x`.
`struct S (i32);`	Create a tuple structure containing an `i32`. Access as `s.0`.
`struct S;`	Create a unit structure that optimizes out of our code.

Code	Description
`enum E { A, B }`	Define an enumeration type with the options, `A` and `B`.
`enum E { A(i32), B }`	Define an enumeration type with `A` and `B`. `A` contains an `i32`.

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