variable '_' is unbound

Raimo Niskanen <>
Tue May 28 08:49:09 CEST 2002


You can only have bound variables in a guard, and you can only bind
variables in the argument list of a function definition. (First hunch).

	foo(Arg) when bar == Arg -> ok;
	foo(<<_:16>> == Arg) -> ok.

or

	foo(Arg) when bar == Arg; 
	              binary(Arg), size(Arg) == 2 -> 
	    ok.

or something.

/ Raimo Niskanen, Erlang/OTP, Ericsson AB



Vance Shipley wrote:
> 
> What is wrong with this:
> 
>         foo(Arg) when bar == Arg; <<_:16>> == Arg -> ok.
> 
> When I try to compile it I get:
> 
>         1> c(t).
>         ./t.erl:4: variable '_' is unbound
>         error
> 
> This is using R8B-1.
> 
>         -Vance



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