[Haskell-cafe] Monad laws

Rafael Almeida almeidaraf at gmail.com
Sun Jun 29 03:38:44 UTC 2014

On Sun, Jun 29, 2014 at 12:11 AM, Brandon Allbery <allbery.b at gmail.com>

> On Sat, Jun 28, 2014 at 10:59 PM, Rafael Almeida <almeidaraf at gmail.com>
> wrote:
>> What is there to be gained by such a law which can't be enforced by the
>> compiler?
> There are lots of things that can't be enforced by the compiler; for
> example, it can't force you to write an Ord instance that implements a
> correct total ordering. Does this make Ord less useful to you? Or pointless?

No. I'm not trying to say Monad laws are useless or pointless. Rather, I am
looking to understand the usefulness of those laws.

People are indeed going to expect that the < operator is transitive. Even
though the compiler can do nothing about it. I'm not sure how to explain
why we need < to be transitive. If you do so, please explain that to me as
well. I always took it for granted that such law must be obeyed.
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