[Python-ideas] Function composition

[Ivan Levkivskyi]

Dear Steve,

Thank you for the feedback and for the links!

I think that both (f at g).__name__ and str(f at g) should be
f.__name__ + ' @ ' + g.__name__
and
str(f) + ' @ ' +str(g)

Concerning the performance, I think that it could be poor, and I don't know
yet how to improve this.

> > Dear all,
> >
> > The matrix multiplication operator @ is going to be introduced in Python
> > 3.5 and I am thinking about the following idea:
> >
> > The semantics of matrix multiplication is the composition of the
> > corresponding linear transformations.
> > A linear transformation is a particular example of a more general
concept -
> > functions.
> > The latter are frequently composed with ("wrap") each other. For
example:
> >
> > plot(real(sqrt(data)))
> >
> > However, it is not very readable in case of many wrapping layers.
> > Therefore, it could be useful to employ
> > the matrix multiplication operator @ for indication of function
> > composition. This could be done by such (simplified) decorator:
>
> I like the idea of @ as a function compose operator.
>
> There have been many requests and attempts at support for function
> composition:
>
> http://code.activestate.com/recipes/574458-composable-functions/
>
> http://code.activestate.com/recipes/52902-function-composition/
>
>
http://code.activestate.com/recipes/528929-dynamic-function-composition-decorator/
>
> http://blog.o1iver.net/2011/08/09/python-function-composition.html
>
> https://mail.python.org/pipermail/python-dev/2009-August/091161.html
>
>
http://stackoverflow.com/questions/2281693/is-it-a-good-idea-to-have-a-syntax-sugar-to-function-composition-in-python
>
>
> The last one is notable, as it floundered in part on the lack of a good
> operator. I think @ makes a good operator for function composition.
>
>
> I think that there are some questions that would need to be answered.
> For instance, given some composition:
>
>     f = math.sin @ (lambda x: x**2)
>
> what would f.__name__ return? What about str(f)?
>
>
> Do the composed functions:
>
>     (spam @ eggs @ cheese)(x)
>
> perform acceptibly compared to the traditional syntax?
>
>     spam(eggs(cheese(x))
>
>
>
> --
> Steve
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-ideas/attachments/20150506/f839bfc6/attachment.html>