[erlang-questions] How about a new warning? Was: Re: trouble with erlang or erlang is a ghetto

Joe Armstrong <>
Wed Aug 3 15:37:50 CEST 2011


Actually I like things as they are. My eye is trained to see bound and
free occurrences of a variable.

On the other hand it would be *excellent* if the color coding in emacs
(whatever) was changed to reflect the
binding status of a variable.

If variables in the LHS of an equals were colored green if they were
unbound and red
if bound then one would see at a glance what was intended.

(( assuming you're not red-green color blind that is )) - or set the
variables in a different type face.


/Joe



2011/8/3 Frédéric Trottier-Hébert <>:
> On 2011-08-02, at 01:59 AM, Richard O'Keefe wrote:
>
>> 2. Is matching against an already-bound variable a check we want?
>
> To me, matching against an already-bound variable is is a valid assertion, as much as 'ok = function_call()' might be, and as implicit as '{ok, Pid}' or '{error, already_started}' might be. Matching on already-bound variables is part of my standard code when trying to crash early when possible, and also part of many basic test suites that simply do pattern matching here and there. To me it's as basic as using the same variable twice in a single pattern (f([A,A,B,B|_]) when A =/= B -> ...), or something similar with records.
>
> I would likely not use the check at all, and if it were to be added, would prefer it to be a compiler argument (which could be enabled in -compile(...).) I foresee little use of such warnings for myself and would dislike to see it becoming a default setting.
>
> --
> Fred Hébert
> http://www.erlang-solutions.com
>
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