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2014-02-01 Roberto Ierusalimschy <>:

>> 1. In mathematics, function composition is right-associative.
> In mathematics, function composition is associative, so it is mostly
> a detail whether it is implemented as right- or left-associative;
> the final result is the same.

I see that I still bear some scars from a course I took in 1967.
The lecturer defined a left-group (which has a left-unit and
a left-inverse) and a right-group (which has a right-unit and
a right-inverse) and took a week to prove that in any left-group,
the left-unit is also a right-unit and the left-inverse is also
a right-inverse. One week later, he presented a second proof
which required one step less and demanded that we cross out
the previous proof. I dropped out after that and took a course
in mathematical physics instead. But clearly irreversible
damage had already been done.