[Haskell-cafe] Re: A question about "monad laws"

Arnar Birgisson arnarbi at gmail.com
Mon Feb 11 10:52:01 EST 2008

Hi all,

On Feb 11, 2008 3:14 PM, apfelmus <apfelmus at quantentunnel.de> wrote:
> I will be mean by asking the following counter question:
>    x + (y + z) = (x + y) + z
> is a mathematical identity. If it is a mathematical identity, a
> programmer need not care about this law to implement addition + . Can
> anyone give me an example implementation of addition that violates this law?

Depends on what you mean by "addition". In general, algebraists call
any associative and commutative operation on a set "addition", and
nothing else. From that POV, there is by definition no "addition" that
violates this law.


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