Hans Mackowiak wrote in post #1101365:
> :false and :true a both resolved as True in an if cause ...
> only nil and false itself are treated as false,
> [],"",{},0,0.0 and others are true too


yes @hans thanks for you help. I know these.

But my question was that - In advance is it possible to test if a method 
take as its argument symbol or not?

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