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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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