[Haskell-beginners] Ord

[Stanisław Findeisen]

On 2011-12-30 12:58, Brandon Allbery wrote:
> 2011/12/30 Stanisław Findeisen <stf-list at eisenbits.com
> <mailto:stf-list at eisenbits.com>>
> 
>     Could anyone please explain to me what is going on here?
> 
> 
> You must, when declaring an instance of Ord, provide *either* a
> definition of (compare) or a definition of (<=).  Both have default
> implementations defined, but in terms of each other; so if you don't
> provide either one in your instance declaration, you get an infinite
> loop when you try to use Ord methods (because (compare) invokes (<=),
> which invokes (compare) ...).

If you don't provide either one, then you get an infinite loop, but this
is a runtime problem, i.e. the code will compile. Right?

How to declare an instance of Ord?

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