1 (<'+')(`:6) 3
4
((<('+';'/')))(`:6) 1 2 3
6
((<('+';'/');'%';'#'))(`:6) 1 2 3
2
(< (<'-');'@:';<(<'+:')) (`:6)1 2 3
_2 _4 _6
/Erling
On 2017-10-21 23:25, Raul Miller wrote:
Ok... i do not know how to approach this without reviewing basics,
so... bear with me.
The question is how does a3 work. And, a3 is:
a3=: (@: (aw f.)) av
aw extracts the left tine of the gerund of a train or analogous sequence:
9!:3]1 5 NB. show both atomic and linear representations
1:a4 NB. raw example verb
┌──────────────┐
│┌─┬──────────┐│
││"│┌──┬─────┐││
││ ││1:│┌─┬─┐│││
││ ││ ││0│_││││
││ ││ │└─┴─┘│││
││ │└──┴─────┘││
│└─┴──────────┘│
└──────────────┘
1:"_
aw 1:a4 bGerund NB. using aw to extract left tine from our example
┌──┐
│1:│
└──┘
And, remember, av derives and adverb from a monadic verb (such that
the adverb result on the adverb argument is what the verb argument
would have been from the verb argument).
The trick seems to be that a3 seemingly produces a gerund result but
it passes that result to @: (and the verb which is derived by @: is
then transformed to an adverb by av).
If I understand right, the only way this can work is if a3 is not
really operating on gerunds but is actually operating on J's internal
structure for tacit functions (they are structured like gerunds but
don't need `:6 to turn them into verbs because they already are verbs
- and this would also apply for adverbs and conjunctions - basically
it's a tree structure with each element of that tree having a type, so
whatever you extract from it has the type of that element).
This ... feels like the sort of obscurity that people talk at length
about (and skirt around) when discussing type theory and higher level
functions. I'm still waffling about what I think about it myself. Jose
really likes it though.
##################
Meanwhile, a6 is something of a wrapper for this aw based mechanic.
It's building up a template verb to build a gerund, using av to make
that an adverb, then using `:6 on the result of executing that
template against the adverb argument.
a6=: ((( ar'a4') ; ] ; ( ar'a3')"_) av) (`:6)
Conceptually, it's sort of like 1 :'a4 u a3' but that rephrasing loses
track of the type and tree structure issues.
Thanks,
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