Intro 19. Tacit Equivalents

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19. Tacit Equivalents
Verbs may be defined either explicitly or tacitly. In the case of a one-sentence explicit definition, of either a monadic or dyadic case, the corresponding tacit definition may be obtained by using the adverb`13 :` as illustrated below. First enter`9!:3 ] 2 5` so as to obtain both the boxed and linear displays of verbs:

       s=: 0 : 0
    (+/y.) % (#y.)
    )

       mean=: 3 : s
       MEAN=: 13 : s

       mean                           MEAN
    +-+-+--------------+           +-----+-+-+
    |3|:|(+/y.) % (#y.)|           |+-+-+|%|#|
    +-+-+--------------+           ||+|/|| | |
    3 : '(+/y.) % (#y.)'           |+-+-+| | |
                                   +-----+-+-+
                                   +/ % #

The explicit form of definition is likely to be more familiar to computer programmers than the tacit form. Translations provided by the adverb`13 :` may therefore be helpful in learning tacit programming.

Exercises

19.1 | Use the display of the tacit definition of`MEAN` to define an equivalent function called`M` . Answer:`M=: +/ % #`

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