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Re: Sv: Sv: Christmas wish: Literate Elisp

From: Adam Porter
Subject: Re: Sv: Sv: Christmas wish: Literate Elisp
Date: Tue, 17 Dec 2019 05:06:45 -0600
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux)

arthur miller <address@hidden> writes:

> It is true, that keeping directives in comments does not break the
> existing parser, but then it is not so much of literate programming,
> is it?

Literate programming is not a matter of syntax.  For example, this
summary in the Wikipedia article seems to describe it well:

  Literate programming is a programming paradigm introduced by Donald
  Knuth in which a computer program is given an explanation of its logic
  in a natural language, such as English, interspersed with snippets of
  macros and traditional source code, from which compilable source code
  can be generated.

  The literate programming paradigm, as conceived by Knuth, represents a
  move away from writing computer programs in the manner and order
  imposed by the computer, and instead enables programmers to develop
  programs in the order demanded by the logic and flow of their
  thoughts. Literate programs are written as an uninterrupted exposition
  of logic in an ordinary human language, much like the text of an
  essay, in which macros are included to hide abstractions and
  traditional source code.

  Literate programming (LP) tools are used to obtain two representations
  from a literate source file: one suitable for further compilation or
  execution by a computer, the "tangled" code, and another for viewing
  as formatted documentation, which is said to be "woven" from the
  literate source. While the first generation of literate programming
  tools were computer language-specific, the later ones are
  language-agnostic and exist above the programming languages.

None of that requires un-prefixed comment syntax.  Consider examples of
actual, full-scale literate programming projects, which are written in a
variety of languages and source code formats.

> If we would just use directives in comments then we already have org +
> babel. But I think 4 extra lines of C code to enable this feature in
> eval-loop was a trivial price to pay :-).

Changing the canonical parser of a widely used language would have
effects reaching far beyond the parser's native software.  Consider all
other software which parses Elisp, e.g. syntax highlighting tools
outside of Emacs, which would not correctly highlight these un-prefixed
comments you propose.  As well, consider other implementations, like
Guile's, which would also have to be adjusted.  Then consider all the
code linting tools which would likely need fixing.  It's not merely a
matter of 4 lines of code in an Emacs source file.

As has been mentioned, benefits such as outlining are easily achieved
with existing tools, some of which are even built-in to Emacs
(e.g. outline-minor-mode for simple outlining in Elisp files, and
org-mode for prose-first, noweb-style source files).

Are you really so concerned about omitting a semicolon at the beginning
of top-level comment lines that you want to change the Elisp parser?

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