Re: Uniform Function Call Syntax (UFCS)

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Date	Mon, 9 Jun 2014 03:10:03 +1000
Subject	Re: Uniform Function Call Syntax (UFCS)
From	Chris Angelico <rosuav@gmail.com>
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On Mon, Jun 9, 2014 at 2:24 AM, jongiddy <jongiddy@gmail.com> wrote:
> A contrived example - which of these is easier to understand?
>
> from base64 import b64encode
>
> # works now
> print(b64encode(str(min(map(int, f.readlines()), key=lambda n: n % 10)), b'?-'))
>
> # would work with UFCS
> f.readlines().map(int).min(key=lambda n: n % 10).str().b64encode(b'?-').print()
>
> You can read the second form left to right

Actually, this is something that I've run into sometimes. I can't
think of any Python examples, partly because Python tends to avoid
unnecessary method chaining, but the notion of "data flow" is a very
clean one - look at shell piping, for instance. Only slightly
contrived example:

cat foo*.txt | gzip | ssh other_server 'gunzip | foo_analyze'

The data flows from left to right, even though part of the data flow
is on a different computer.

A programming example might come from Pike's image library [1]. This
definitely isn't what you'd normally call good code, but sometimes I'm
working at the interactive prompt and I do something as a one-liner.
It might look like this:

Stdio.write_file("foo.png",Image.PNG.encode(Image.JPEG.decode(Stdio.read_file("foo.jpg")).autocrop().rotate(0.5).grey()));

With UFCS, that could become perfect data flow:

read_file("foo.jpg").JPEG_decode().autocrop().rotate(0.5).grey().PNG_encode().write_file("foo.png");

I had to solve the syntactic ambiguity here by importing all the
appropriate names, which does damage readability a bit. But you should
be able to figure out what this is doing, with only minimal glancing
at the docs (eg to find out that rotate(0.5) is rotating by half a
degree).

So the proposal does have some merit, in terms of final syntactic
readability gain. The problem is the internal ambiguity along the way.

ChrisA

[1] http://pike.lysator.liu.se/generated/manual/modref/ex/predef_3A_3A/Image/Image.html

Thread

Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-06 23:45 -0700
  Re: Uniform Function Call Syntax (UFCS) Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-07 13:20 -0600
    Re: Uniform Function Call Syntax (UFCS) Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-06-08 13:27 +1200
      Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 01:26 -0700
        Re: Uniform Function Call Syntax (UFCS) Paul Sokolovsky <pmiscml@gmail.com> - 2014-06-08 15:06 +0300
          Re: Uniform Function Call Syntax (UFCS) Marko Rauhamaa <marko@pacujo.net> - 2014-06-08 18:56 +0300
            Re: Uniform Function Call Syntax (UFCS) Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-08 10:38 -0600
            Re: Uniform Function Call Syntax (UFCS) Paul Sokolovsky <pmiscml@gmail.com> - 2014-06-08 19:40 +0300
            Re: Uniform Function Call Syntax (UFCS) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-06-09 04:33 +0000
              Re: Uniform Function Call Syntax (UFCS) Marko Rauhamaa <marko@pacujo.net> - 2014-06-09 09:25 +0300
                Re: Uniform Function Call Syntax (UFCS) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-06-09 09:09 +0000
                Re: Uniform Function Call Syntax (UFCS) Chris Angelico <rosuav@gmail.com> - 2014-06-09 19:13 +1000
                Re: Uniform Function Call Syntax (UFCS) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-06-09 13:37 +0000
                Re: Uniform Function Call Syntax (UFCS) Chris Angelico <rosuav@gmail.com> - 2014-06-10 01:08 +1000
          Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 09:24 -0700
            Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 09:34 -0700
            Re: Uniform Function Call Syntax (UFCS) Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-08 10:54 -0600
            Re: Uniform Function Call Syntax (UFCS) Chris Angelico <rosuav@gmail.com> - 2014-06-09 03:10 +1000
              Re: Uniform Function Call Syntax (UFCS) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-06-09 03:20 +0000
                Re: Uniform Function Call Syntax (UFCS) Chris Angelico <rosuav@gmail.com> - 2014-06-09 13:44 +1000
                Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 23:38 -0700
                Re: Uniform Function Call Syntax (UFCS) Roy Smith <roy@panix.com> - 2014-06-08 23:45 -0400
      Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 02:25 -0700
        Re: Uniform Function Call Syntax (UFCS) Roy Smith <roy@panix.com> - 2014-06-08 10:59 -0400
          Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 08:39 -0700
            Re: Uniform Function Call Syntax (UFCS) Chris Angelico <rosuav@gmail.com> - 2014-06-09 02:48 +1000
              Re: Uniform Function Call Syntax (UFCS) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-06-09 03:53 +0000
                Re: Uniform Function Call Syntax (UFCS) Chris Angelico <rosuav@gmail.com> - 2014-06-09 14:53 +1000
                Re: Uniform Function Call Syntax (UFCS) Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-09 08:24 -0600
                Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-09 23:43 -0700
            Re: Uniform Function Call Syntax (UFCS) Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-08 11:08 -0600
            Re: Uniform Function Call Syntax (UFCS) Chris Angelico <rosuav@gmail.com> - 2014-06-09 03:13 +1000
            Re: Uniform Function Call Syntax (UFCS) Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-08 11:24 -0600
              Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 13:35 -0700
    Re: Uniform Function Call Syntax (UFCS) jongiddy <jongiddy@gmail.com> - 2014-06-08 01:15 -0700
      Re: Uniform Function Call Syntax (UFCS) Paul Sokolovsky <pmiscml@gmail.com> - 2014-06-08 14:52 +0300
      Re: Uniform Function Call Syntax (UFCS) Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-08 11:00 -0600

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