// BinOp has methods 'a()' and 'b()', both return 'Ast'
// UnOp has method 'n()' returning 'int'

a, b, n are fields not methods

Nice kata

I use node v6 can pass all testcase with the same code which failed with node v8.1.3

It's my fault. The result can pass the testcase now. but there is new problem with node v8.1.3

The output

Time: 992ms Passed: 1009 Failed: 1

and

Congratulations, You pass the test! 

After you submit your solution, DON'T FORGET UPVOTE&RANK THIS KATA, THANK YOU!

this one can return 2*(13-(7/7)), your answer is: 2*(13-7/7)
what's difference between 2*(13-(7/7)) and 2*(13-7/7)?

STDERR:

/tmp/haskell11766-19-qhv1ia.ictgc4bo6r/Codewars/G964/Ball/Test.hs:11:1: Warning:
Tab character

/tmp/haskell11766-19-qhv1ia.ictgc4bo6r/Codewars/G964/Ball/Test.hs:12:1: Warning:
Tab character

/tmp/haskell11766-19-qhv1ia.ictgc4bo6r/Codewars/G964/Ball/Test.hs:13:1: Warning:
Tab character

...

什么鬼

+1

Array.prototype.toString = function() {
  return '';
}

And I got

CaughtCheatingError: JSON.stringify() has been disabled for this Kata

How to rank up to 1 dan?

Nice kata