[RFC] codingconventions: add lambda guidelines
Checks
Commit Message
Now in patch form!
Any further comments?
---
htdocs/codingconventions.html | 60 +++++++++++++++++++++++++++++++++++
1 file changed, 60 insertions(+)
base-commit: 62250c79a7483076f1b2b11496e4a1123c9df6a0
Comments
On Thu, Jan 11, 2024 at 04:33:10PM -0500, Jason Merrill wrote:
> Now in patch form!
>
> Any further comments?
It looks good to me, but it doesn't say if we want to put a space
after } and before () if we're invoking the lambda (I suppose we
want that space). As in
... = [&] (tree arg) { ... } ();
Thanks,
> ---
> htdocs/codingconventions.html | 60 +++++++++++++++++++++++++++++++++++
> 1 file changed, 60 insertions(+)
>
> diff --git a/htdocs/codingconventions.html b/htdocs/codingconventions.html
> index f5a356a8..2bbf6670 100644
> --- a/htdocs/codingconventions.html
> +++ b/htdocs/codingconventions.html
> @@ -76,6 +76,7 @@ the conventions separately from any other changes to the code.</p>
> <li><a href="#Template_Form">Templates</a></li>
> <li><a href="#ExternC">Extern "C"</a></li>
> <li><a href="#Namespace_Form">Namespaces</a></li>
> + <li><a href="#Lambda_Form">Lambdas</a></li>
> </ul>
> </li>
> </ul>
> @@ -1488,6 +1489,65 @@ with a right brace, optional closing comment, and a new line.
> Definitions within the body of a namespace are not indented.
> </p>
>
> +<h4 id="Lambda_Form">Lambdas</h4>
> +
> +<p>There should be a space between the lambda-introducer and the parameter
> + list, if any.</p>
> +<p>Lambdas that do not outlive their enclosing function should
> + typically use <code>[&]</code> implicit capture.</p>
> +
> +<blockquote><pre><code>auto l = [&] (tree arg) { ... };
> +</code></pre></blockquote>
> +
> +<p>If a lambda does not fit on one line, the left brace should be indented like
> +the body of a for-statement.</p>
> +
> +<blockquote><pre><code>auto l = [&] (tree arg)
> + {
> + ...
> + };
> +</code></pre></blockquote>
> +
> +<p>This also applies if the lambda is the last argument, and only lambda
> +argument, to a function.</p>
> +
> +<blockquote><pre><code>std::for_each (start, end, [&] (tree arg)
> + {
> + ...
> + });
> +</code></pre></blockquote>
> +
> +To get the above behavior from
> +<a href="https://www.gnu.org/software/emacs/manual/html_mono/ccmode.html">
> + GNU Emacs CC Mode</a>, you can add this to your <code>.emacs</code>:
> +
> +<blockquote><pre><code>(defun lambda-offset (elem)
> + "If the opening brace of a lambda is on a new line, indent it one step."
> + (if (assq 'inline-open c-syntactic-context) '+ 0))
> +(add-hook 'c++-mode-hook
> + '(lambda () (c-set-offset 'inlambda 'lambda-offset)))
> +</code></pre></blockquote>
> +
> +<p>If the multi-line lambda is not the last argument, or there are multiple
> +lambda arguments, you are encouraged to make them local variables, as
> +the <code>l</code> examples above. If you do pass them directly, they should
> +be indented like other parameters.
> +
> +<blockquote><pre><code>my_algo (start, end,
> + [&] (tree arg)
> + {
> + thing one...
> + },
> + [&] (tree arg)
> + {
> + thing two...
> + });
> +</code></pre></blockquote>
> +
> +<p>See also the
> + <a href="https://sourceware.org/gdb/wiki/Internals%20GDB-C-Coding-Standards#Indentation_of_lambdas_as_parameters">
> + GDB coding standards</a>.</p>
> +
> <h2 id="python">Python Language Conventions</h2>
>
> <p>Python scripts should follow <a href="https://peps.python.org/pep-0008/">PEP 8 – Style Guide for Python Code</a>
>
> base-commit: 62250c79a7483076f1b2b11496e4a1123c9df6a0
> --
> 2.39.3
>
Marek
On Thu, 11 Jan 2024, Jason Merrill wrote:
> Now in patch form!
It appears quite clear to me.
(At first I thought we need to escape the '&' in "[&] (tree arg)" as
"&", but checking with validator.w3.org apparently not so in this
specific context.)
Gerald
@@ -76,6 +76,7 @@ the conventions separately from any other changes to the code.</p>
<li><a href="#Template_Form">Templates</a></li>
<li><a href="#ExternC">Extern "C"</a></li>
<li><a href="#Namespace_Form">Namespaces</a></li>
+ <li><a href="#Lambda_Form">Lambdas</a></li>
</ul>
</li>
</ul>
@@ -1488,6 +1489,65 @@ with a right brace, optional closing comment, and a new line.
Definitions within the body of a namespace are not indented.
</p>
+<h4 id="Lambda_Form">Lambdas</h4>
+
+<p>There should be a space between the lambda-introducer and the parameter
+ list, if any.</p>
+<p>Lambdas that do not outlive their enclosing function should
+ typically use <code>[&]</code> implicit capture.</p>
+
+<blockquote><pre><code>auto l = [&] (tree arg) { ... };
+</code></pre></blockquote>
+
+<p>If a lambda does not fit on one line, the left brace should be indented like
+the body of a for-statement.</p>
+
+<blockquote><pre><code>auto l = [&] (tree arg)
+ {
+ ...
+ };
+</code></pre></blockquote>
+
+<p>This also applies if the lambda is the last argument, and only lambda
+argument, to a function.</p>
+
+<blockquote><pre><code>std::for_each (start, end, [&] (tree arg)
+ {
+ ...
+ });
+</code></pre></blockquote>
+
+To get the above behavior from
+<a href="https://www.gnu.org/software/emacs/manual/html_mono/ccmode.html">
+ GNU Emacs CC Mode</a>, you can add this to your <code>.emacs</code>:
+
+<blockquote><pre><code>(defun lambda-offset (elem)
+ "If the opening brace of a lambda is on a new line, indent it one step."
+ (if (assq 'inline-open c-syntactic-context) '+ 0))
+(add-hook 'c++-mode-hook
+ '(lambda () (c-set-offset 'inlambda 'lambda-offset)))
+</code></pre></blockquote>
+
+<p>If the multi-line lambda is not the last argument, or there are multiple
+lambda arguments, you are encouraged to make them local variables, as
+the <code>l</code> examples above. If you do pass them directly, they should
+be indented like other parameters.
+
+<blockquote><pre><code>my_algo (start, end,
+ [&] (tree arg)
+ {
+ thing one...
+ },
+ [&] (tree arg)
+ {
+ thing two...
+ });
+</code></pre></blockquote>
+
+<p>See also the
+ <a href="https://sourceware.org/gdb/wiki/Internals%20GDB-C-Coding-Standards#Indentation_of_lambdas_as_parameters">
+ GDB coding standards</a>.</p>
+
<h2 id="python">Python Language Conventions</h2>
<p>Python scripts should follow <a href="https://peps.python.org/pep-0008/">PEP 8 – Style Guide for Python Code</a>