Note that declaring arguments is just like declaring vals: the argument name, a colon, and the type returned from the method.
Does the last clause ( "type returned from the method" ) belong to the context of the sentence, which is about method arguments' declaration being like vals' declaration ?
First para, 2nd line goes:
Does the last clause ( "type returned from the method" ) belong to the context of the sentence, which is about method arguments' declaration being like vals' declaration ?