old_contents: const test = require('tape')
  var app = require('../app')
  
  test('prefix test', function (t) {
    app('+ 1 3', function (rst) {
      t.equal(rst, 4)
    })
  
    app('+ - -1 |3| 2^5', function (rst) {
      t.equal(rst, 28)
    })
  
    app('+ - -1 |-3| 2^5', function (rst) {
      t.equal(rst, 28)
    })
  
    t.end()
  })
  
  test('postfix test', function (t) {
    app('1 3 +', function (rst) {
      t.equal(rst, 4)
    })
  
    t.end()
  })
  
  test('infix test', function (t) {
    app('1+3', function (rst) {
      t.equal(rst, 4)
    })
  
    app('1+(-3)', function (rst) {
      t.equal(rst, -2)
    })
  
    app('1 - -3', function (rst) {
      t.equal(rst, 4)
    })
  
    app('-1 - -3', function (rst) {
      t.equal(rst, 2)
    })
  
    app('-1 - -3 + 2^5', function (rst) {
      t.equal(rst, 34)
    })
  
    app('-1 - -3 + pow[2, 4] + 1', function (rst) {
      t.equal(rst, 19)
    })
  
    app('-1 - |-3| + 2^5', function (rst) {
      t.equal(rst, 28)
    })
  
    app('-1 - abs[-3] + 2^5', function (rst) {
      t.equal(rst, 28)
    })
  
    app('-1 - abs[-3] + pow[2, 5]', function (rst) {
      t.equal(rst, 28)
    })
  
    app('-1 - abs(-3) + 2^5', function (rst) {
      t.equal(rst, 28)
    })
  
    app('-1 - abs(-3) + pow[2, 5]', function (rst) {
      t.equal(rst, 28)
    })
  
    app('-1 - abs(-3) + pow(2, 5) - (5 + 5)', function (rst) {
      t.equal(rst, 18)
    })
  
    app('-1', function (rst) {
      t.equal(rst, -1)
    })
  
    app('100', function (rst) {
      t.equal(rst, 100)
    })
  
    t.end()
  })
  
new_contents: const test = require('tape')
  var app = require('../app')
  
  test('prefix test', function (t) {
    app('+ 1 3', function (rst) {
      t.equal(rst, 4)
    })
  
    app('+ - -1 |3| 2^5', function (rst) {
      t.equal(rst, 28)
    })
  
    app('+ - -1 |-3| 2^5', function (rst) {
      t.equal(rst, 28)
    })
  
    t.end()
  })
  
  test('postfix test', function (t) {
    app('1 3 +', function (rst) {
      t.equal(rst, 4)
    })
  
    t.end()
  })
  
  test('infix test', function (t) {
    app('1+3', function (rst) {
      t.equal(rst, 4)
    })
  
    app('1+(-3)', function (rst) {
      t.equal(rst, -2)
    })
  
    app('1 - -3', function (rst) {
      t.equal(rst, 4)
    })
  
    app('-1 - -3', function (rst) {
      t.equal(rst, 2)
    })
  
    app('-1 - -3 + 2^5', function (rst) {
      t.equal(rst, 34)
    })
  
    app('-1 - -3 + pow[2, 4] + 1', function (rst) {
      t.equal(rst, 19)
    })
  
    app('-1 - |-3| + 2^5', function (rst) {
      t.equal(rst, 28)
    })
  
    app('-1 - abs[-3] + 2^5', function (rst) {
      t.equal(rst, 28)
    })
  
    app('-1 - abs[-3] + pow[2, 5]', function (rst) {
      t.equal(rst, 28)
    })
  
    app('-1 - abs(-3) + 2^5', function (rst) {
      t.equal(rst, 28)
    })
  
    app('-1 - abs(-3) + pow[2, 5]', function (rst) {
      t.equal(rst, 28)
    })
  
    app('-1 - abs(-3) + pow(2, 5) - (5 + 5)', function (rst) {
      t.equal(rst, 18)
    })
  
    app('-1 - abs(-3) + pow(2, 5) - 10 % 3', function (rst) {
      t.equal(rst, 27)
    })
  
    app('-1', function (rst) {
      t.equal(rst, -1)
    })
  
    app('100', function (rst) {
      t.equal(rst, 100)
    })
  
    t.end()
  })
  
subject: add testcase for modulo