About your closing question, you can do
isint =: (= <.) : [:
isint 2 0.5
1 0
2 isint 3
|domain error: isint
| 2 isint 3
The definition of isint specifies [: as the dyadic case, and [; rejects every
argument with a domain error.
Kip Murray
Sent from my iPad
On Nov 30, 2012, at 10:14 PM, Alex Giannakopoulos <aeg...@blueyonder.co.uk>
wrote:
> On 30 November 2012 16:17, Bo Jacoby <bojac...@yahoo.dk> wrote:
>
>> J is a rich language, and it might be a good idea to define an elementary
>> subset for beginners.
>
>
> Couldn't agree more.
> A simple startup configuration file. Define verbs for trig functions so
> they don't look stupidly arbitrary.
> Some other elementary functions too, like polar2rect and rect2polar
> conversions that act on vectors (none of this xfy binary stuff here
> please), you know, stuff like you can find on *calculators*.
> Define dot-product, matrix-multiplication, cross-product, determinant, etc,
> as user-friendly built-in verbs. When I am a beginner, I DO NOT, repeat
> NOT want to know about the . operator at the level of the jdict, it is a
> highly advanced subject, intriguing - yes, but not for newbies. Yet I do
> want to do matrix ops. I was told this was a language for linear algebra.
> It would probably be a good idea, then, if we could do some linalg -
> straight out of the box - without serious brain damage. I have had abuse
> hurled at me by math teachers who have seen J's linalg primitives (LOL).
> Add some nice libs for equation solving while we're at it. Simultaneous
> and also some numeric solvers. This is what people want. A language, not
> an assembler for a language.
>
>
>> J is a nice calculator for elementary computations. You can do a lot of
>> computing without knowing anything about binomial coefficients and taylor
>> expansions and capped forks.
>
>
> Agree with the first two, NO way on the third. Even the 13 verb gives you
> capped verbs, there is no way to begin learning J without it. Also they
> solve the problem of having to figure if you should use At or Atop,
> invaluable for a beginner who hasn;t quite mastered rank yet.
>
> This problem, which once again gives rise to a long thread, could easily be
> solved by a highly visible Programming FAQ page, with lots of links to.
> Deal with capped forks, @ and @: and why you can't have things like +/ a
> b c You know, the questions people *keep asking*. Remove ancient
> irrelevant stuff like the use of x. and y. We are not at J401 any more.
>
>
>> If you need to understand everything in order to be happy, then you may be
>> unhappy. I taught my son elementary APL when he was 10 years old, and he
>> loved it!
>
> Would he have been just as happy at 14 when he had to use the cosine rule
> to solve a triangle? Would he really prefer
> cosrule_getang =: 13 : '_2&o.(((+/*:}.y)-*:{.y) % */ 2, }.y)'
> or
> cosrule_getang =: [: _2&o. (([: +/ [: *: }.) - [: *: {.) % [: */ 2 , }.
> to
> cosrule_getang := (Aa,B,C) -> acos((B^2+C^2-Aa^2)/(2.0*B*C));
> Just wondering...
>
> These are simple enough things to do, and I speak as a J newcomer. There's
> not many languages you can say that about after two and a half years! The
> Zen of J, grasshopper.
>
> Incidentally, is there a way to cap a monadic hook on the left?
> For example (=<.) was mentioned, but obviously it allows dyadic arguments,
> and fails if they are offered.
> Short of wrting monad : 'y=<.y' is there a way I can keep it monadic (and
> implicit)?
> ----------------------------------------------------------------------
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