"GOTO Kentaro"  wrote in
....
> I don't think that is explicit conversion because we couldn't know
> which method would be called.  For example, I was surprised by

Well at least you are not alone in your surprise ...

>  % ruby -e 'class A; def to_int() 10 end end; p("%o" % A.new)'
>  "12"

....

/Christoph


/Ps Thank you very much for this example - I was not
aware that Ruby had such a rich ``formatting string''
mechanism.