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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