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From: Rodrigo Morales <moralesrodrigo1100@gmail.com>
To: org-mode-email <emacs-orgmode@gnu.org>
Subject: Re: [feature request] The :pre header argument
Date: Fri, 19 Feb 2021 08:33:28 -0500	[thread overview]
Message-ID: <CAGxMbPZ2TLiZSKEcFGxZzS-=MxWFcucy7_AXUgtjUOqmOk2eTg@mail.gmail.com> (raw)
In-Reply-To: <878s7ljbd7.fsf@gmail.com>

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You can read this message with proper formatting here (
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).

On Thu, 18 Feb 2021 at 16:52, Rodrigo Morales <moralesrodrigo1100@gmail.com>
wrote:

>
> This message contains my thoughts on a feature request which I think
> would be useful: The =:pre= header argument, it would be used to
> execute a code block before the code block at point is executed. It
> would be similar to the behavior of the =:post= header argument.
>
> Here's a simple example that shows how =:pre= could be used
>
> #+NAME: clean-path-experiments
> #+begin_src dash
> if [ ! -z "$my__experiments" ] && [ -d "$my__experiments" ]; then
>   find ~/e -mindepth 1 -maxdepth 1 -exec rm -rf {} +
> fi
> #+end_src
>
> #+NAME: tree-command
> #+begin_src dash
> tree -a --noreport
> #+end_src
>
> #+NAME: create-dir-for-minimal-reproducible-example
> #+HEADER: :pre clean-path-experiments()
> #+HEADER: :post tree-command()
> #+begin_src python
> import os
>
> [os.makedirs(_) for _ in ["a/foo", "a/bar", "b"]]
> [os.mknod(_) for _ in ["a/1.txt", "a/2.txt", "a/foo/b.txt", "a/bar/b.txt",
> "b/b.txt"]]
> #+end_src
>
> #+RESULTS: create-dir-for-minimal-reproducible-example
> #+begin_example
> .
> ├── a
> │   ├── 1.txt
> │   ├── 2.txt
> │   ├── bar
> │   │   └── b.txt
> │   └── foo
> │       └── b.txt
> └── b
>     └── b.txt
> #+end_example
>
> I think that such header argument would be useful because of two
> main reasons:
>
> * It would improve readability of code blocks by explicitly expressing
> dependency
>
> By having a header argument for the sole purpose of expressing
> dependencies between code blocks, the readability of header arguments
> would be improved. Recall that it is currently possible to express
> such dependency by calling a code block through a =:var <<name>>=
> header argument but I think that =:var= header argument must only be
> used for defining variables (be it from results obtained from
> different code blocks or literals).
>
> The first code block shown below show the differences between using
> =:var= and =:pre= for the same scenario. =first-code-block= uses the
> =:var= header argument while the =second-code-block= uses the =:pre=
> header argument.
>
> #+NAME: first-code-block
> #+begin_src org
> For our experimentation, let's start with an empty directory and let's
> execute the first step.
>
> ,#+NAME: first-step
> ,#+HEADER: :results silent
> ,#+HEADER: :var e=clean-path-experiments
> ,#+begin_src dash
> touch first-step.txt
> ,#+end_src
>
> We know execute the second step.
>
> ,#+NAME: second-step
> ,#+HEADER: :results silent
> ,#+HEADER: :var e=first-step
> ,#+begin_src dash
> touch second-step.txt
> ,#+end_src
>
> Finally, we execute the third step.
>
> ,#+NAME: third-step
> ,#+HEADER: :results silent
> ,#+HEADER: :var e=second-step
> ,#+begin_src dash
> touch third-step.txt
> ,#+end_src
> #+end_src
>
> #+NAME: second-code-block
> #+begin_src org
> For our experimentation, let's start with an empty directory and let's
> execute the first step.
>
> ,#+NAME: first-step
> ,#+HEADER: :results silent
> ,#+HEADER: :pre clean-path-experiments()
> ,#+begin_src dash
> touch first-step.txt
> ,#+end_src
>
> We know execute the second step.
>
> ,#+NAME: second-step
> ,#+HEADER: :results silent
> ,#+HEADER: :pre first-step()
> ,#+begin_src dash
> touch second-step.txt
> ,#+end_src
>
> Finally, we execute the third step.
>
> ,#+NAME: third-step
> ,#+HEADER: :results silent
> ,#+HEADER: :pre second-step()
> ,#+begin_src dash
> touch third-step.txt
> ,#+end_src
> #+end_src
>
> In my opinion, the second code block looks more readable than the
> first one.
>
> * it would add importance to the =:post= header argument
>
> The =:post= header argument can be used in Org Mode 9.3 to execute a
> given code block after the code block at point is executed; having a
> header argument that does the opposite of the =:post= header argument
> would give relevance to the =:post= header argument.
>
> --
> Greetings,
> Rodrigo Morales.
>
> IRC: rdrg109 (freenode)
>

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  reply	other threads:[~2021-02-19 13:38 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-18 21:48 Rodrigo Morales
2021-02-19 13:33 ` Rodrigo Morales [this message]
2021-02-20  1:50   ` Rodrigo Morales
2021-04-05  4:49     ` Ihor Radchenko

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