sexp-template/test/evaluatorTest.js

const test = require('tape')
const helpers = require('./helpers')

const AST = require('../src/ast')
const OsloError = require('../src/osloError')

test('applies functions from core library', t => {
  t.plan(1)

  const tree = helpers.evaluate('(+ 1 2)')
  t.deepEqual(tree[0], new AST.Number({ value: 3 }))
})

test('applies lambda functions', t => {
  t.plan(1)

  const tree = helpers.evaluate('((lambda (x y) (+ x y)) 1 2)')
  t.deepEqual(tree[0], new AST.Number({ value: 3 }))
})

test('define', t => {
  t.plan(2)

  let tree = helpers.evaluate('(define x 5) (+ x 1)')
  t.deepEqual(tree[0], new AST.Number({ value: 6 }))

  tree = helpers.evaluate('(define plusOne (lambda (x) (+ x 1))) (plusOne 5)')
  t.deepEqual(tree[0], new AST.Number({ value: 6 }))
})

test('conditionals', t => {
  t.plan(3)

  let tree = helpers.evaluate('(if #t 1 0)')
  t.deepEqual(tree[0], new AST.Number({ value: 1, line: 1 }))

  tree = helpers.evaluate('(if #f 1 0)')
  t.deepEqual(tree[0], new AST.Number({ value: 0, line: 1 }))

  tree = helpers.evaluate('(if (= (+ 4 9) (- 20 7)) (+ 10 9) (- 4 2))')
  t.deepEqual(tree[0], new AST.Number({ value: 19 }))
})

test('let bindings', t => {
  t.plan(1)

  const tree = helpers.evaluate('(let ((x 1) (y 2)) (+ x y))')
  t.deepEqual(tree[0], new AST.Number({ value: 3 }))
})

test('let bindings go out of scope after the let block', t => {
  t.plan(1)

  const tree = helpers.evaluate('(let ((x 1)) x) x')
  t.deepEqual(
    tree,
    new OsloError({ line: 1, message: "Symbol 'x' is not bound" }),
  )
})

test('factorial', t => {
  t.plan(1)

  const tree = helpers.evaluate(`
    (define factorial
      (lambda (x)
        (if (= x 0)
          1
          (* x (factorial (- x 1))))))
    (factorial 5)

  `)
  t.deepEqual(tree[0], new AST.Number({ value: 120 }))
})