must either all be present or all be absent. If present, each name
stands for one item (parameter or result) of the specified type and
all non-<a href="#Blank_identifier">blank</a> names in the signature
must be <a href="#Uniqueness_of_identifiers">unique</a>.
If absent, each type stands for one item of that type.
Parameter and result
lists are always parenthesized except that if there is exactly

    As a duck with its eyelids, so he with his nose
    Trims his belt and his buttons, and turns out his toes.'

              [later editions continued as follows
    When the sands are all dry, he is gay as a lark,
    And will talk in contemptuous tones of the Shark,
    But, when the tide rises and sharks are around,
    His voice has a timid and tremulous sound.]

    As a duck with its eyelids, so he with his nose
    Trims his belt and his buttons, and turns out his toes.'

              [later editions continued as follows
    When the sands are all dry, he is gay as a lark,
    And will talk in contemptuous tones of the Shark,
    But, when the tide rises and sharks are around,
    His voice has a timid and tremulous sound.]