= Let expressions

A `let` expression defines a value with a local scope.

[source]
.Example
....
nix-repl> let x = 3; in x*x
9

nix-repl> let x = 3; y = 2; in x*x + y
11
....

You can also nest `let` expressions.
The previous expression is equivalent to the following.

[source]
.Example
....
nix-repl> let x = 3; in let y = 2; in x*x + y
11
....

[IMPORTANT]
====
A variable defined inside a `let` expression will "shadow" an outer variable with the same name.

[source]
.Example
....
nix-repl> x = 100

nix-repl> let x = 3; in x*x
9

nix-repl> let x = 3; in let x = 7; in x+1
8
....
====

A variable in a let expression can refer to another variable in the expression.
This is similar to how recursive attribute sets work.

[source]
.Example
....
nix-repl> let x = 3; y = x + 1; in x*y
12
....

// TODO Discuss inheriting attributes https://nixos.org/manual/nix/stable/language/constructs#inheriting-attributes