Re: [PATCH] noweb documentation update

[Kaushal Modi <kaushal.modi@gmail.com>]

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A quick update.. the attached patch has minor formatting fixes over the
previous one.

Please use this patch for review.

Thanks.

On Thu, Jun 22, 2017 at 3:01 PM Kaushal Modi <kaushal.modi@gmail.com> wrote:

> Hello,
>
> Thanks. My comments are below, and the updated patch is attached.
>
-- 

Kaushal Modi

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From 9580d645d001defb098d83f90d58e6a36f6220e3 Mon Sep 17 00:00:00 2001
From: Kaushal Modi <kaushal.modi@gmail.com>
Date: Thu, 22 Jun 2017 14:52:32 -0400
Subject: [PATCH] Improve noweb documentation

* doc/org.texi (noweb, noweb-ref, Noweb reference syntax): Add
examples and improve wording.  Clarify the use of noweb style
references with code block arguments.
---
 doc/org.texi | 145 +++++++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 122 insertions(+), 23 deletions(-)

diff --git a/doc/org.texi b/doc/org.texi
index b722b5da93..d41a28998a 100644
--- a/doc/org.texi
+++ b/doc/org.texi
@@ -16188,36 +16188,50 @@ code blocks are evaluated, tangled, or exported.
 
 @itemize @bullet
 @item @code{no}
-Default.  No expansion of ``Noweb'' syntax references in the body of the code
+Default.  No expansion of ``noweb'' syntax references in the body of the code
 when evaluating, tangling, or exporting.
 @item @code{yes}
-Expansion of ``Noweb'' syntax references in the body of the @samp{src} code
+Expansion of ``noweb'' syntax references in the body of the @samp{src} code
 block when evaluating, tangling, or exporting.
 @item @code{tangle}
-Expansion of ``Noweb'' syntax references in the body of the @samp{src} code
+Expansion of ``noweb'' syntax references in the body of the @samp{src} code
 block when tangling.  No expansion when evaluating or exporting.
 @item @code{no-export}
-Expansion of ``Noweb'' syntax references in the body of the @samp{src} code
+Expansion of ``noweb'' syntax references in the body of the @samp{src} code
 block when evaluating or tangling.  No expansion when exporting.
 @item @code{strip-export}
-Expansion of ``Noweb'' syntax references in the body of the @samp{src} code
+Expansion of ``noweb'' syntax references in the body of the @samp{src} code
 block when expanding prior to evaluating or tangling.  Removes ``noweb''
 syntax references when exporting.
 @item @code{eval}
-Expansion of ``Noweb'' syntax references in the body of the @samp{src} code
+Expansion of ``noweb'' syntax references in the body of the @samp{src} code
 block only before evaluating.
 @end itemize
 
 @subsubheading Noweb prefix lines
-Noweb insertions now honor prefix characters that appear before
-@code{<<reference>>}.  This behavior is illustrated in the following example.
-Because the @code{<<example>>} noweb reference appears behind the SQL comment
-syntax, each line of the expanded noweb reference will be commented.
+Noweb insertions now honor prefix characters that appear before the ``noweb''
+syntax reference.
 
-This @samp{src} code block:
+This behavior is illustrated in the following example.  Because the
+@code{<<example>>} noweb reference appears behind the SQL comment syntax,
+each line of the expanded noweb reference will be commented.
+
+With:
 
 @example
+#+NAME: example
+#+BEGIN_SRC text
+this is the
+multi-line body of example
+#+END_SRC
+@end example
+
+this @samp{src} code block:
+
+@example
+#+BEGIN_SRC sql :noweb yes
 -- <<example>>
+#+END_SRC
 @end example
 
 expands to:
@@ -16230,17 +16244,60 @@ expands to:
 Since this change will not affect noweb replacement text without newlines in
 them, inline noweb references are acceptable.
 
+This feature can also be used for management of indentation in exported code snippets.
+
+With:
+
+@example
+#+NAME: if-true
+#+BEGIN_SRC python :exports none
+print('Do things when True')
+#+END_SRC
+
+#+NAME: if-false
+#+BEGIN_SRC python :exports none
+print('Do things when False')
+#+END_SRC
+@end example
+
+this @samp{src} code block:
+
+@example
+#+BEGIN_SRC python :noweb yes :results output
+if True:
+    <<if-true>>
+else:
+    <<if-false>>
+#+END_SRC
+@end example
+
+expands to:
+
+@example
+if True:
+    print('Do things when True')
+else:
+    print('Do things when False')
+@end example
+
+and evaluates to:
+
+@example
+Do things when True
+@end example
+
 @node noweb-ref
 @subsubsection @code{:noweb-ref}
 @cindex @code{:noweb-ref}, src header argument
 
 When expanding ``noweb'' style references, Org concatenates @samp{src} code
-blocks by matching the reference name to either the block name or the
+blocks by matching the reference name to either the code block name or the
 @code{:noweb-ref} header argument.
 
 For simple concatenation, set this @code{:noweb-ref} header argument at the
 sub-tree or file level.  In the example Org file shown next, the body of the
-source code in each block is extracted for concatenation to a pure code file.
+source code in each block is extracted for concatenation to a pure code file
+when tangled.
 
 @example
  #+BEGIN_SRC sh :tangle yes :noweb yes :shebang #!/bin/sh
@@ -16756,25 +16813,67 @@ references in the @samp{src} code block before evaluation.
 For the header argument @code{:noweb no}, Org does not expand ``noweb'' style
 references in the @samp{src} code block before evaluation.
 
-The default is @code{:noweb no}.
+The default is @code{:noweb no}.  Org defaults to @code{:noweb no} so as not
+to cause errors in languages where ``noweb'' syntax is ambiguous.  Change
+Org's default to @code{:noweb yes} for languages where there is no risk of
+confusion.
 
 Org offers a more flexible way to resolve ``noweb'' style references
 (@pxref{noweb-ref}).
 
-Org can handle naming of @emph{results} block, rather than the body of the
-@samp{src} code block, using ``noweb'' style references.
-
-For ``noweb'' style reference, append parenthesis to the code block name for
-arguments, as shown in this example:
+Org can include the @emph{results} of a code block rather than its body.  To
+that effect, append parentheses, possibly including arguments, to the code
+block name, as show below.
 
 @example
 <<code-block-name(optional arguments)>>
 @end example
 
-Note: Org defaults to @code{:noweb no} so as not to cause errors in languages
-such as @samp{Ruby} where ``noweb'' syntax is equally valid characters.  For
-example, @code{<<arg>>}.  Change Org's default to @code{:noweb yes} for
-languages where there is no risk of confusion.
+Note that when using the above approach to a code block's results, the code
+block name set by @code{#+NAME} keyword is required; the reference set by
+@code{:noweb-ref} will not work.
+
+Here is an example that demonstrates how the exported content changes when
+``noweb'' style references are used with parentheses versus without.
+
+With:
+
+@example
+#+NAME: some-code
+#+BEGIN_SRC python :var num=0 :results output :exports none
+print(num*10)
+#+END_SRC
+@end example
+
+this code block:
+
+@example
+#+BEGIN_SRC text :noweb yes
+<<some-code>>
+#+END_SRC
+@end example
+
+expands to:
+
+@example
+print(num*10)
+@end example
+
+Below, a similar ``noweb'' style reference is used, but with parentheses,
+while setting a variable @code{num} to 10:
+
+@example
+#+BEGIN_SRC text :noweb yes
+<<some-code(num=10)>>
+#+END_SRC
+@end example
+
+Note that now the expansion contains the @emph{results} of the code block
+@code{some-code}, not the code block itself:
+
+@example
+100
+@end example
 
 For faster tangling of large Org mode files, set
 @code{org-babel-use-quick-and-dirty-noweb-expansion} variable to @code{t}.
-- 
2.13.0