J By Example is interesting, but I think you should remove the K, which
will only be confusing. But it's not for the novice anyway.
I like the idea of simple programs. The Python page didn't do much for
me; the programs were either too easy or too hard. Perhaps we can do
better.
The hard part is coming up with the problems to solve. Here's Project
Euler problem 1:
NB. Find the sum of all the multiples of 3 or 5 below 1000.
NB. Solutions will be by creating a sieve of the numbers, then summing.
NB. Solution 0, typed at the console:
mask3 =. 1000 $ 3 {. 1 NB. Create the pattern 1 0 0 and repeat it
mask3 NB. Display it
1 0 0 1 0 0 1 0 0 1 0 0 1 0 0 1 0 0 1 0 0 1 0 0 1 0 0 1 0 0 1 0 0...
mask5 =. 1000 $ 5 {. 1 NB. Create the pattern 1 0 0 0 0 and repeat
mask5
1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0...
mask35 =. mask3 +. mask5 NB. Boolean OR
mask35
1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 0...
I. mask35 NB. The numbers that correspond to the 1s
0 3 5 6 9 10 12 15 18 20 21 24 25 27 30 33 35 36 39 40 42 45 48...
+/ I. mask35 NB. Their total
233168
NB. The same, typed into the console as 1 line
+/ I. (1000 $ 3 {. 1) +. (1000 $ 5 {. 1)
233168
NB. Solution 2. The same, collected into a verb (i. e. a program)
PE1 =: verb define
+/ I. (1000 $ 3 {. 1) +. (1000 $ 5 {. 1)
)
PE1 '' NB. Execute the program
233168
NB. Solution 3. Generalized to find all numbers less than the
NB. right argument (denoted y) that are multiples of any
NB. number in the left argument (denoted x)
PE1 =: dyad define
masks =. (y $ {.&1)"0 x NB. One mask for each number in x
combinedmasks =. +./ masks NB. Boolean OR of all of these
+/ I. combinedmasks NB. The total
)
3 5 PE1 1000
233168
3 5 7 PE1 2000
1083288
NB. Solution 4. The same, represented in tacit form
NB. Wouldn't it be cool to learn how to do this?
PE1 =: +/ @: I. @ (+./) @: (($ {.&1)"0) ~ NB. The entire program!
3 5 PE1 1000
233168
3 5 7 PE1 2000
1083288
Henry Rich
On 9/7/2014 9:38 AM, 'Pascal Jasmin' via Programming wrote:
I like the python page, but I also like the J by example link I added to
http://www.jsoftware.com/jwiki/Vocabulary/HowNuVoc a couple of weeks ago.
----- Original Message -----
From: Ian Clark <[email protected]>
To: [email protected]
Cc:
Sent: Sunday, September 7, 2014 5:35 AM
Subject: Re: [Jprogramming] J Kernel
Minimal Beginning J fills an important gap. One I had on my list to fill
urgently -- but Devon's got there first, with a surprisingly simple starter
set. Good Work, Devon!
Initially I was tempted to second-guess Devon by tweaking his list. Soon I
was convinced that if somebody could improve upon it, that somebody wasn't
me.
People coming from C, Basic, Python, etc etc will straightaway say: hey
where's a[3] ? Should we give them { and } ? By the same token, people
coming from Fortran (and Basic) will say: hey where's GOTO? Should we give
them (goto_name.)?
Bear in mind that Minimal Beginning J is the first rung on a long ladder.
The hitherto missing first rung! Since it already offers }. {. and # -- why
not leave { and } to the second rung?
What's still badly needed though is some evidence this starter set is good
enough for some recognizable programming of a general nature. Not just fit
for knocking down a few carefully chosen straw-men.
I know little or no Python, so a visit to www.python.org is most
instructive -- and very sobering. Almost the first thing a beginner like me
sees is a list of "Simple programs" (
https://wiki.python.org/moin/SimplePrograms).
We could do worse than rip-off this list of coding tasks *exactly* as it
stands and show them in Minimal Beginning J. A sort of "Minimal Beginning
Rosetta", if-you-will. I know "me-too" isn't that sexy a sport -- but is
the first rung really the place for "me-only"?
On Thu, Sep 4, 2014 at 4:12 AM, Scott Locklin <[email protected]> wrote:
Nice work, Devon.
One of the things I would like to do eventually is a sort of "J for
Matlab/R programmers." I figure J is vastly more useful as a general
purpose language than these, but it is also first rate for all kinds of
numerics and mathematical applications. There is a large population of math
people who would prefer something better than Matlab or R, but for most
languages, math is sort of a second class citizen.
-SL
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