Comments on: The J programming language

By: Elmer Fittery

Elmer Fittery — Fri, 11 Apr 2008 23:55:26 +0000

According to:

http://www.byte.com/art/9603/sec11/art10.htm

The public-domain version 7 of the J programming language. BYTEmark is a collection of 10 tests that exercises the CPU, FPU, cache, and system memory; J is a complete interpreter that is the last public-domain release of the J language’s source code prior to J’s becoming a commercial package.

By: Harry Reed

Harry Reed — Fri, 25 May 2007 16:53:26 +0000

Hi, I discovered J a few years ago and am quite impressed. Sadly, as is mentioned, “…no Free Software implementation exists.” I am contemplating writing an open source version of J. However, before I start this Herculean task, does anybody know if an effort to produce an open source J has already been started?

By: Aidan

Aidan — Sat, 28 Apr 2007 16:15:18 +0000

Hi Samuel Thanks for all your advice so far. My project is due shortly on J but i an having one last error. The folllowing line returns a domain error and i cannot understand why.
getIHW =: ( (0 {:: NetParams) ,&> (1 {:: NetParams)) $ ((0 {:: NetParams) * (1 {:: NetParams)) {.!.0 [

Can you please offer some advice for one last time i would grateful.

By: Aidan

Aidan — Tue, 27 Mar 2007 15:26:33 +0000

Hi I am back again. Just one small question, in order for me to muliply a column i change it to a row using |: as i want to use them all at once. So my column 1
0
2
4
is changed to 1 0 2 4. It works but I am just wondering is there not another way to do this? Given that I am only a novice with J I am sure there is. Can you please help I would really appreciate it.

By: Aidan

Aidan — Mon, 12 Mar 2007 10:51:08 +0000

Thank you very much you’re a life saver.

By: Samuel Tardieu

Samuel Tardieu — Fri, 09 Mar 2007 14:22:33 +0000

You can define it as an adverb easily: (which does what you ask, including embed your getInxSmallest and getInxLargest functions)

   f =: 1 : ']i.<.`(>.)@.x/'
   0 f 10 20 5 30 15
2
   1 f 10 20 5 30 15
3

I’ll let you analyze the adverb.

By: Aidan

Aidan — Fri, 09 Mar 2007 13:35:53 +0000

Hi i am having a bit of trouble with a program i am working on. Basically i have 2 function getInxSmallest and getInxLargest they take in an array on numbers and reutrn the position of the largest or lowest depending on which function you use. Now i must must create a function that returns the position of the smallest number in the array when a 0 is entered and the largest when a 1 is entered.
for example lets say you create an array v1 =: 5 2 1 3 when 0 FUNCTIONNAME v1 is entered the answer should return 2 as the smallest number 1 is in position 2. Can you please help i would greatly appreciate it.

By: Gregor Lingl

Gregor Lingl — Mon, 27 Feb 2006 11:41:42 +0000

During my first encounter with J I succeeded in shortening the

+/1e6< ,!/~>:i.100

program by more than 10%.

+/1e6<,!/~i.101

Please notice, that !/~>:i.100 doesn’t use the
complete table of binomial coefficients (i. e. Pascals’s triangle)
Example:

!/~>:i.10
1 2 3 4 5 6 7 8 9 10
0 1 3 6 10 15 21 28 36 45
0 0 1 4 10 20 35 56 84 120
0 0 0 1 5 15 35 70 126 210
0 0 0 0 1 6 21 56 126 252
0 0 0 0 0 1 7 28 84 210
0 0 0 0 0 0 1 8 36 120
0 0 0 0 0 0 0 1 9 45
0 0 0 0 0 0 0 0 1 10
0 0 0 0 0 0 0 0 0 1

in contrast to:

!/~i.11
1 1 1 1 1 1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 10
0 0 1 3 6 10 15 21 28 36 45
0 0 0 1 4 10 20 35 56 84 120
0 0 0 0 1 5 15 35 70 126 210
0 0 0 0 0 1 6 21 56 126 252
0 0 0 0 0 0 1 7 28 84 210
0 0 0 0 0 0 0 1 8 36 120
0 0 0 0 0 0 0 0 1 9 45
0 0 0 0 0 0 0 0 0 1 10
0 0 0 0 0 0 0 0 0 0 1

regards
Gregor Lingl