[Haskell-cafe] Why are && and || right-associative?

Jerzy Karczmarczuk jerzy.karczmarczuk at unicaen.fr
Sat Apr 13 13:34:53 UTC 2019

Le 13/04/2019 à 14:29, Joachim Durchholz cites Richard O'Keefe :

>> I would
>> be astonished if you had been told that
>>     a ** b ** c
>> was defined to be
>>     a ** (b ** c)
>> back in 1950-something,
> Actually we were told, with the reasoning that (a ** b) ** c is the 
> same as a ** (b * c), I recall that that was presented as "nothing new 
> there so not worth defining it that way).
> Truth be told, that was the 1970-something for me.

'70?? Even worse...

I began my school in '50-something, and I was duly taught that. And 
without "nothing new here", which I find rather unpleasantly surprising. 
My teacher pointed out that (a**b)**c is equal to a**(b*c), so the left 
associativity would not be extremely clever.

Joachim says in his previous posting:

> I guess my intuition is more based on math, where associativity is an 
> irrelevant detail
Now, this is for me a *REALLY* peculiar vision of math. Irrelevant 
detail?? Where? In the categorical calculus perhaps? Abandon the 
associativity of morphisms, and you will see...

In Lie algebras maybe? Well, add the associativity to it, and kill all 
the quantum theory.

Good luck.

There are many people, mainly young (e.g. my students) who have a 
tendency to "see mathematics" through "computer lenses" - parsing, 
implementable data structures, recursion as an implementation detail, 
etc. For the mathematical culture this is harmful.

Jerzy Karczmarczuk

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