| Message ID | 20240111213310.1566285-1-jason@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [RFC] codingconventions: add lambda guidelines | expand |
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
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>