[Haskell-cafe] Is there a name for this property: x + x - x == x

Dmitry Vyal akamaus at gmail.com
Wed Jun 4 14:45:29 UTC 2014

On 06/04/2014 06:34 PM, Omari Norman wrote:
> It's not quite idempotence, because more than one function is involved.
> It's a common property and I figure I can write a higher order 
> function to build QuickCheck tests for it.  I was just wondering if it 
> has a name.

Hello Omari,
I guess it's a corollary of two group axioms.

There exists an identity element e such what for any a  a + e == e + a == a.
And for any element a inverse element -a exists, such that a + (-a) == e.

Take a look at http://en.wikipedia.org/wiki/Group_%28mathematics%29

Why not compose a name out of these two? :)

More information about the Haskell-Cafe mailing list