A little AST for Jordan Scales' evaluator exercise that evaluates to `PenPinappleApplePen!`, with `Pen`, `Pinapple` and `Apple` stored in variables.

PenPinappleApplePen.js

// Check out this article to write your own evaluator for it! http://thatjdanisso.cool/programming-languages/

const ppap = {
  type: 'Let',
  name: 'p',
  value: {
    type: 'String',
    content: 'Pen'
  },
  expression: {
    type: 'Let',
    name: 'p2',
    value: {
      type: 'String',
      content: 'Pineapple'
    },
    expression: {
      type: 'Let',
      name: 'a',
      value: {
        type: 'String',
        content: 'Apple'
      },
      expression: {
        type: 'Append',
        first: {
          type: 'Append',
          first: {
            type: 'Variable',
            name: 'p'
          },
          second: {
            type: 'Variable',
            name: 'p2'
          }
        },
        second: {
          type: 'Append',
          first: {
            type: 'Variable',
            name: 'a'
          },
          second: {
            type: 'Excite',
            expression: {
              type: 'Variable',
              name: 'p'
            }
          }
        }
      }
    }
  }
}