Roger,
I'd call sum a "variable" in APL if-and-only-if ([]NC 'sum') returns 2.
In Dyalog APL (I don't have it installed on my Mac) I seem to recall
you can indeed write:
sum←+
but []NC 'sum' would afterwards return 3, telling me it's a function
(...whatever else it might have been before).
So... "what do you call a name in APL whose referent is a function?"
-- A function name.
Moreover I think most APLs won't let you change "sum", say, from a
variable name to a function name by reassigning it. Even if functional
assignment is permitted. The statement (sum←+) causes an error if sum
is already defined in the workspace as a variable, and you haven't
freed-up the name 'sum' for reuse by localisation or []EX.
I use "value" (...but only in an APL context, let me emphasise) to
mean "something that can be assigned to a variable" (...and it still
remains a variable). I think a lot of APLers would agree with that.
It's a more restricted meaning of "value" than you imply in the J
context, which it seems to me means anything acceptable to the right
of a copula. Or, more precisely, any entity that is returned by
evaluating a phrase which can validly stand to the right of a copula.
You say that "noun" in J corresponds directly and exactly with "array"
in APL. Was that a mistake... don't you mean "array or scalar"?
(...commonly expressed as "vector or scalar" -- "array" not being a
proper APL term, and [APL] "vector" not being restricted to 1-D
arrays.) Surely you don't mean me to infer that 99 is not a noun in J
because it is not an "array" in APL?
I'm not interested in challenging Ken's appeal to his implicit
understanding of English Grammar (which I deny is necessarily mine, or
indeed anyone else's) to convey programming ideas. He's allowed to do
that. I just want a precise enough notion of "noun/pronoun" -- as it
applies to J -- so I can point to something in J code and say with
confidence "that's a noun" or "that's a pronoun".
Ian
2010/10/25 Roger Hui <[email protected]>:
>> But Ken talks of "analogies", and seems to use the word "noun"
>> to mean a value or quantity: the result of an expression, not the
>> variable -- or named memory location -- it's stored in. What, in J,
>> corresponds to an APL "variable"?
>
> "Noun" in J does not mean value. It corresponds
> directly and exactly to "array" in APL. A value can
> be a verb (function), for example, "the value of the
> sentence +/ is a verb that does summation".
>
> Regarding your last question, It depends on how
> "variable" is used in APL. If you say sum←+/ 2 3 4,
> I think you'd call "sum" a variable. But if you say
> sum←+/, is "sum" still a variable? If not, what is
> the difference, and what do you call a name in APL
> whose referent is a function? If yes, doesn't it
> sound jarring to your ears? (It does to mine.)
>
> And, a question Ken used to ask: if sum←1 2 3,
> what is variable about "sum"?
>
> Some APL texts also calls .5 and 1 2 3 and 'abc'
> "variables, that is, used "variable" and "array"
> as synonyms. Ken's question is even more pertinent
> in those cases: If ever .5 has a different value
> ("varied"), I expect to get system errors shortly
> thereafter.
>
> There is a table in the dictionary section II. Grammar:
> http://www.jsoftware.com/help/dictionary/dict2.htm
>
> PARTS of SPEECH
>
> 50 fahrenheit Nouns/Pronouns
> + - * % bump Verbs/Proverbs
> / \ Adverbs
> & Conjunction
> ( ) Punctuation
> =: Copula
>
>
>
> ----- Original Message -----
> From: Ian Clark <[email protected]>
> Date: Sunday, October 24, 2010 12:21
> Subject: [Jgeneral] "J In A Day" --crits please
> To: General forum <[email protected]>
>
>> First draft of an article for eventual submission to VECTOR entitled
>> "J In A Day".
>>
>> http://www.jsoftware.com/jwiki/JinaDay
>>
>> It is "work-in-progress". It represents an "alpha" offering, not a
>> "release" or "publication". It's aimed squarely at the APLer who
>> doesn't know any J.
>>
>> There won't be many such on this list. But right now I'm keen to get
>> the J right.
>>
>> The prevalent message to APLers coming to J is: un-learn everything
>> you know about APL (it's not helpful) and learn J from first
>> principles. I think this erects an unnecessary barrier to the
>> dwindling(?) band of APLers ignorant of J.
>>
>> Of course the barriers may be there anyway. I recall my first exposure
>> to J aroused antipathy in me. I can't quite remember why. A Kuhnian
>> paradigm-shift may be inescapable--or at least the need for one. The
>> article deliberately avoids being starry-eyed so as not to raise the
>> APLer's hackles. But this is not meant as provocation to the J-er.
>>
>> There's a fairly defiant "admonition" (as MoinMoin calls it) to J
>> experts -- but don't be put off. I would really appreciate your
>> comments. So get your anoraks on... ;)
>>
>> Of course, if an APL-er knowing absolutely no J were to work through
>> it, and confirm (or deny) it was of use to them... that would
>> get me
>> on like 7-league boots.
>>
>> BTW I use the J terms "proverb" and "pronoun" in it. I need to
>> know if
>> I'm using them correctly. See my separate posting.
>>
>> Thanks, Brian, for the Iverson ref. From the horse's mouth, so to
>> speak. But Ken talks of "analogies", and seems to use the word "noun"
>> to mean a value or quantity: the result of an expression, not the
>> variable -- or named memory location -- it's stored in. What, in J,
>> corresponds to an APL "variable"?
>>
>> Ian
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