I wrote:
> Ok, ok, last one (for now :):
So call me a liar.
> A tacit sentence contains no variables.
No. Let's go back to fundamentals:
A tacit expression can take arguments, but doesn't mention them.
So +`- isn't tacit. Which makes sense: we intuit that something about nouns
excludes them from being tacit. Which is why my
second attempt at a definition, using the parse table, almost works.
The special thing about nouns, that prevents them from being tacit, is that
they can't take arguments. Nouns are the lowest level
of the part-of-speech hierarchy. Nouns can take no arguments, verbs can take
nouns as arguments, operators can take nouns or
verbs as arguments, and nothing can take operators as arguments.
This definition permits us to identify tacit operators, too. For example, in
J4, we could say @:D.1 which means "the derivative
of the composition", and has the same flavor as 1+* at the next level of
heirarchy (composition of operators, with implied verb
arguments, analogous to composition of verbs with implied noun arguments).
-Dan
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