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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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