Intro 17. Names and Displays

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17. Names and Displays
In addition to the normal names used thus far, there are three further classes:

1) | `$:` is used for self-reference, allowing a verb to be defined recursively without necessarily assigning a name to it, as illustrated in Section 22.
2) | The names`x.` and`y.` are used in explicit definition, discussed in Section 18. They denote the arguments used in explicit definition.
3) | A name (such as`ab_cd_`)`` that has two underbars of which one is the final character, is a locative. Names used in a locale`F` can be referred to in another locale`G` by using the suffix`F` in a locative name of the form`pqr_F_` ,`` thus avoiding conflict with otherwise identical names in the locale`G` .`` See Section I of Part II for further details.

The form of the display invoked by entering a name alone is established by`9!:3` ,`` as described in Appendix A. For example:

       mean=: +/ % #

       9!:3 (4)                    Tree form

       mean
      +- / --- +
    --+- %
      +- #

       9!:3 (5)                    Linear form

       mean
    +/ % #

Multiple displays are also possible:

       9!:3 (5 4 2)

       mean

    +/ % #
      +- / --- +
    --+- %
      +- #
    +-----+-+-+
    |+-+-+|%|#|
    ||+|/|| | |
    |+-+-+| | |
    +-----+-+-+

Exercises

17.1 | Experiment with the use of locatives.

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