Implement let expression

[mauriciotogneri]

Let node

• assignments: [AssignmentNode]
• node: Node

AssignmentNode

• variable: String
• node: Node

Approach

• Constraint: none of the variables in the expression can be called like any of the parameters of the function
• When substituting in a let expression
  • Substitute all bindings in the expression of the first assignment
  • Add the first variable (with its node substituted) to the bindings
  • Use the new bindings to substitute in the second assignment
  • Add the second variable (with its node substituted) to the bindings
  • Continue for all variables
  • Use the final substitution for the let expression node

foo(n) = let
             x = bar(n)
         in
             calculate(x, x + 1)

foo(n) = let
             x = bar(n)
         in
             let
                 y = test(n)
             in
                 calculate(x, x + 1, y, y + 1)

foo(n) = let
             x = bar(n)
             y = test(n)
         in
             calculate(x, x + 1, y, y + 1)

foo(a, b) = let
                x = a + b
                y = x * 2
            in
                num.pow(y, 2)

foo(a, b) = let
                x = process(a, b)
            in
                if (result.isSuccess(x))
                    console.write('Success: ' + result.get(x))
                else
                    console.write('Failure: ' + result.get(x))

frequency(list) = frequency.helper(list, {})

frequency.helper(list, result) =
    if (list.isEmpty(list))
        result
    else
        let
            first = list.first(list)
            tail = list.tail(list)
        in
            let count = if (map.containsKey(result, first))
                            result[first] + 1
                        else
                            1
            in
                frequency.helper(tail, map.set(result, first, count))

main = frequency([1, 2, 2, 3, 1, 4, 5, 2, 2, 5])