[erlang-questions] What is wrong with this list?

Ulf Wiger (TN/EAB) <>
Wed Sep 5 10:46:39 CEST 2007


 wrote:
> This is a case where the line number information could be
 > useful. Also a warning might be useful during compilation
 > time, a same kind of warning that you get in C for code like
> if (a=b) ...

The compiler does issue warnings whenever it can detect
that a clause will not match.

Specifically:

-module(warns).

-compile(export_all).

f() ->
     [java|python] = [1,2,3,4,5].


results in this warning:


11> c(warns).
./warns.erl:6: Warning: no clause will ever match
{ok,warns}

The initial post in this thread showed a failed
pattern match in the _shell_. That code would
have triggered a warning if compiled.

BR,
Ulf W



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