Let Binding

A let binding is of the form

let
    var = expression
in
    expression
end

or

let
    (var,...,var) = expression
in
    expression
end

The first case evaluates the expression with the variable bound. The second case destructures a tuple. The expression on the right hand side of the equation must evaluate to a tuple, and the variables get bound to the values in the tuple.

A let binding can have multiple bindings.

let
    var1 = expression1,
    var2 = expression2
in
    expression
end

is shorthand for

let
    var1 = expression1
in
    let
      var2 = expression2
    in
        expression
    end
end