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

Robert Virding <>
Thu Aug 4 00:17:21 CEST 2011


I am assuming that the check only applies for variables in matches with '=' and not in case/receive patterns. In that case I would not mind having such a warning turnable on/off at will. I seldom test for values in '=' matches, only in case/receive.

The emacs colouring is difficult given how erlang handles variables and evaluation ordering etc.

Robert

----- Original Message -----
> 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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> > erlang-questions mailing list
> > 
> > http://erlang.org/mailman/listinfo/erlang-questions
> >
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