Of the new modifier trains, I've found ^:^:_ as "while". A simple test
code: increment while less than 8. (With some errors one need kill the
j session.)
>: (^:^:_) (<&8) 2
8
While=: ^:^:_
u. While v.
u.^:v.^:_
Date: Wed, 15 Feb 2023 13:12:37 +0100
From: Jan-Pieter Jacobs<janpieter.jac...@gmail.com>
To:programm...@jsoftware.com
Subject: Re: [Jprogramming] Atop parsing
Message-ID:
<cans99cyu9dmv0kgq+sh4dtvxiueqvcoz_if5iwzw_cvuhh4...@mail.gmail.com>
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The reason it's hard to find anything else on modifier trains is that they
have been removed from the language a long time ago (with j501 in 2002,
apparently), and only reintroduced recently with j903.
Before the reintroduction, the only modifier trains were bidents:
- partially applied conjunctions, yielding adverbs; and
- chained adverbs, being applied to their left argument in order.
They were left over because they are simple, intuitive and easy to remember
(guessing here, as I wasn't around in the J scene yet).
These are explained well inhttps://www.jsoftware.com/help/learning/15.htm .
The adverbs each and every defined in the standard library library are
useful examples of the first kind of bidents:
type&.<'each'
adverb
each
&.>
The rabbit hole of general modifier trains is deep: they are not completely
intuitive (at least to me) and require a thorough understanding of the
parsing and execution in J, especially when chaining more than three. They
are also not indispensable, as you can write explicit conjunctions and
adverbs to do anything such tacit modifiers would do. I have yet to find a
useful, non-trivial purpose for them... Of course, feel free to use them if
you like the challenge, but there are far more important areas to get to
know in J, like rank. Or all the wonderful labs (in the menu, help > studio
labs).
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