[Python-ideas] Function composition (was no subject)

[Koos Zevenhoven]

On 9.5.2015 5:58, Stephen J. Turnbull wrote:
> Koos Zevenhoven writes:
>
>   > As a random example, (root @ mean @ square)(x) would produce the right
>   > order for rms when using [2].
>
> Hardly interesting. :-)  The result is an exception, as root and square
> are conceptually scalar-to-scalar, while mean is sequence-to-scalar.
>
> I suppose you could write (root @ mean @ (map square)) (xs), which
> seems to support your argument.  But will all such issues and
> solutions give the same support?  This kind of thing is a conceptual
> problem that has to be discussed pretty thoroughly (presumably based
> on experience with implementations) before discussion of order can be
> conclusive.
>

Well, you're wrong :-)

Working code:

from numpy import sqrt, mean, square

rms = sqrt(mean(square(x)))

The point is that people have previously described sqrt(mean(square(x))) 
as root-mean-squared x, not squared-mean-root x. But yes, as I said, 
it's just one example.

-- Koos