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Re: [O] [PATCH] Support for 'using namespace *' in ob-C.el

From: Nicolas Goaziou
Subject: Re: [O] [PATCH] Support for 'using namespace *' in ob-C.el
Date: Sun, 23 Jul 2017 16:44:08 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux)


Jay Kamat <address@hidden> writes:

> However, it would be nice to add a "using namespace std" to this
> source code block, so it can become:
> #+BEGIN_SRC C++ :includes <iostream> :namespaces std
>   cout << "Hello world\n";
> Which makes it cleaner and easier to read, especially for very short
> code snippets, using a bunch of std tools.

Good idea.

> One concern that I have is that "using namespace *;" is only available
> in C++ and not C, but there isn't an easy way I could find to limit
> it's usage to only C++ blocks without a bunch of restructuring, so
> this will fail if you attempt to set a namespace on a plain C block.

I suggest to add the following to "ob-C.el" so that `org-lint' can issue
a warning whenever :namespaces is used in a C block.

  (defconst org-babel-header-args:C '((includes . :any))
    "C-specific header arguments.")

  (defconst org-babel-header-args:C++
    `(,(append '((namespaces . :any))
    "C++-specific header arguments.")

> Also, this contribution puts me very close to the 15 line limit before
> I need to get FSF papers signed. I intend to sign papers soon, but I'm
> a little busy right now, and I'll get around to submitting the request
> later on.

Thank you. FYI, in many cases, the whole process is very quick and not

> Subject: [PATCH] ob-C.el: Add support for specifying namespaces in C/C++
> * lisp/ob-C.el (org-babel-C-expand-C): Add a :namespaces export option
>   to C++ org babel blocks. Namespaces specified here will be added to
>   the file in the format 'using namespace %s;'. Multiple namespaces
>   can be specified, separated by spaces.

Some comments follow.

> +     (namespaces (org-babel-read
> +               (or (cdr (assq :namespaces params))
> +                   (org-entry-get nil "namespaces" t))
> +                nil)))

Using `org-entry-get' is no longer supported. You can replace the `or'

  (cdr (assq :namespaces params))

> +             ;; namespaces
> +             (mapconcat
> +              (lambda (inc) (format "using namespace %s;" inc))
> +              namespaces "\n")

Nitpick: I would put the "\n" on another line.

Could you also provide an ORG-NEWS entry for the feature?


Nicolas Goaziou

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