Hi,

instance Show Stat where
  show (a, b) = "the value of " ++ a ++ " is " ++ show b

I pretty sure you need also enable TypeSynonymInstances extension. One way to do it is to add "{-# LANGUAGE TypeSynonymInstances #-}" just at the beginning of your module.

Best wishes

2015-12-04 1:16 GMT+03:00 Murilo Winter <murilo.winter@gmail.com>:
Hello,

As part of my exercise, I have to create an instance of the show typeclass for a given data type defined as:
  1. type stat = (String, Int)  
If it was a data type, like:
  1. data TrafficLight = Red | Yellow | Green  

It would be as simple as doing:
  1. instance Show TrafficLight where  
  2.     show Red = "Red light"  
  3.     show Yellow = "Yellow light"  
  4.     show Green = "Green light" 

However, I do not know how to declare the instance for a type, and then how to access its elements (String and Int).

This is what I have so far, which does not work:
  1. instance Show Stat where  
  2.     show stat(a,b) = a
instance Show Stat where
  show stat(a b) = b

(imagine, for example, I desire to write" the value of "String" is "Int").

Thanks,

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