Warning: This is intended as a joke and contains no useful information.

   f=. 0 : 'I=:$0'
   g=. 0 : 'B=:0$0'
   f-:g
0

Paul Gauthier
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Dan Bron <[EMAIL PROTECTED]> 
Sent by: [EMAIL PROTECTED]
03/14/2007 03:31 PM
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Subject
[Jgeneral] A typical challenge (was:  definition of a:)






Let me put this a different way.  Solve the following puzzle in J.

Demonstrate the difference between:

                    I  =:   $0

and

                    B  =:  0$0

The difference must be guarunteed (predicted, fully supported) by the 
Dictionary, excluding the foreign conjunction  !:  and the Appendicies. To 
put it another way, you may not leverage bugs in the implementation or J's 
introspection.

Assume you're running under jconsole -jprofile: that is, you may not 
depend on any sentence having been executed before your own.  Put another 
way, do not rely on the names normally defined by the J standard library. 

For example, if I'd said find the difference between  I  and

                    L  =:  ''

you could easily demonstrate it thus:

                    I =&{. L
                 0

and support it by quoting Section II.B or the Vocabulary entry for  {.  :

                    2302 239 qdoj '{.'     NB.  
http://www.jsoftware.com/help/dictionary/dictb.htm
                 In an overtake (in which the number to be taken exceeds
                 the number of  items), extra items consist of fills; 
zeros
                 if y is numeric, a: if it is boxed, spaces if literal, 
and 
                 s: ' ' if symbol. 

 
                    2725 163 qdoj 'dictb'  NB.  
http://www.jsoftware.com/help/dictionary/d521.htm
                 padding with an appropriate fill element:  space for a
                 character array, 0 for a numeric array, and a boxed empty
                 list for a boxed array.

but the task will not be so trivial with  I  vs  B  .  Remember that you 
may not use  !:  . 

-Dan
 

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