[Jprogramming] Draft reference card for J9.04

[Henry Rich]

Thanks to you, Hauke, Don for the comments.

The Glossary has links to definitions.

We made the decision that !&| would be better known that the standard 
math symbols

Certain special combinations ARE shown; which ones would you like?

2 ?. 8 is 2 4.  What's wrong with that?

The Re and Im are a standard math notation.

The formulas is for the Moore-Penrose inverse, which is what %. y computes

If you want a simpler card, make one!

Henry Rich





On 8/9/2022 5:28 PM, Elijah Stone wrote:
> It claims that x|y is x mod y, but it is in fact y mod x.
>
> I don't think an example result of 2 4 for ?. is helpful.
>
> In 'scalar dyadic verbs', why is footnote b attached to 'rnd', but 
> footnote c is attached to '?.'?  They should be consistent.
>
> I think that instead of 'Rank of ?. _, others 0', it should be 'Rank 0 
> (except ?.)'.  Begin with the common case, then list exceptions.
>
> The way the words 'Shape, Length, Rank' are spaced makes it look like 
> they are labels for the columns of the table they accompany. I don't 
> know what the solution is; it might be a good idea to left-align the 
> table headings, or possibly tighten the horizontal spacing.
>
> The vertical spacing, on the other hand, is too tight; it makes the 
> tables difficult to scan.  I would loosen it, even if it requires 
> adding a third page.
>
> Names of standard library functions (datatype, load, etc.) don't link 
> anywhere.
>
> 'r. π' should presumably be 'r. 1p1', as it is meant to be a j sentence?
>
> Maybe it helps somebody, but I find the colouration on the second 
> page--in particular for modifier trains and conjunctions--too busy; I 
> would mute it a bit.  But this is a matter of taste.
>
> For @., rather than '[x] Vn y' with a footnote to explain what n is, I 
> would say '[x] Vn y [ n=. [x] v y'.  I would also use subscripts for 
> 0, 1, and n. And I would replace n with i, since n is conventionally 
> used to name an argument to a conjunction.
>
> u::v needs a space after u.  I suggest that it should be stylised 'u . 
> v', not 'u .v' (and analogously for other conjunctions that start with 
> inflections).
>
> '[x] u^:v y' is '[x] u^:([x] v y) y', which is not what the reference 
> says. Perhaps there should be a second row giving the common case of v 
> as a predicate.
>
> In 'apply [x&]u til x&u y false', the second 'x&' needs to be 
> bracketed as optional.
>
> In place of '[x&]u ...(n times) y', I would say '[x] u [x] u ...(n 
> times) y'. I don't think the & is helpful, and and showing multiple 
> instances of u makes it clearer exactly what it is that is happening n 
> times.
>
> In the 'sort and grade' section, for a moment, I thought 'abcd' was 
> intended as a left argument to all the verbs.  I guess this is because 
> it is the middle-most item.  Maybe simply reordering would fix it.  
> Perhaps move /:@/: up above the sorts, together with the grades.  Then 
> 'abcd' is no longer in the middle, and /:~ has pride of place as the 
> last row (since it is likely to be the most common use of /: et co).
>
> In 'atomic compound forms a?b', it looks like there is an application 
> of the verb ?.  I would at the least italicise it rather than bolding it.
>
> I am curious where the convention of using black capital letters R and 
> I to indicate the real and imaginary parts of a complex number comes 
> from.
>
> On Tue, 9 Aug 2022, Henry Rich wrote:
>
>> Viktor Grigorov has a draft version of the new J Reference Card.  
>> Please criticize it.
>>
>> The source for the card is a LaTeX document, and will be freely 
>> available for editing.
>>
>> A PDF version is at 
>> https://drive.google.com/file/d/1bpyfmksD-XEJaJJ972jOy3b2_KWfV0Wi/view?usp=sharing
>>
>> Henry Rich
>>
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