Source code for standard instances of typeclass instances

Question

I was interested to know about declaring an Ord instance for (a,b) , and I would like to quickly look through the hackers to confirm my intuition that the comparison is first on a , and then, in case of equality, on b . In particular, I went here . Since hackers have links to the source code for declarations and data functions, I assumed that there will also be source code for instance declarations, but I can not find them. Is there a reason why they are not there, or I just did not look complicated enough? type Answer = Either Explanation Directions :)

Answer 1

I went to the foreplay , clicked the source link for the Ord typeclass , it scrolls a bit, and found that it is defined as

 deriving instance (Ord a, Ord b) => Ord (a, b) 

It uses the extension StandaloneDeriving . It basically generates the same code as the type

 data (a, b) = (a, b) deriving Ord 

Answer 2

The Ord instance for tuples is deduced according to the rules from the language specification that are returned with respect to Gofer .

 instance (Eq a, Eq b) => Eq (a,b) where (x,y) == (u,v) = x==u && y==v instance (Ord a, Ord b) => Ord (a,b) where (x,y) <= (u,v) = x<u || (x==u && y<=v) 

Answer 3

The Haskell 98 report states in section 10.1 :

Class methods automatically introduced by derived instances of Eq and Ord - (==), (/ =), cf. (<), (<=), (>), (> =), max and min. The last seven operators are defined so as to compare their arguments lexicographically with respect to a given set of constructors, with earlier constructors in the data type declaration, counting less than later ones.

Derived comparisons always cross constructors from left to right.

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All derived operations of class Eq and Ord are strict in both arguments.