Re: [Bug-apl] Operator Idiosyncrasies

[Louis de Forcrand]

Mike Duvos <address@hidden> writes:

> 
> Just in case it isn't instantly obvious what's wrong in the prior post, 
GNU APL is returning the wrong thing for dyadic reduce with a left 
argument of zero and a scalar right argument.If f is a scalar function, 
and X is a non-empty vector, or a scalar which gets treated as a 1-element 
vector, then the expression...      0 f/ XShould return a vector of length 
1+⍴,X filled in with the identity for f.
Some examples...      0 +/ 990 0      0 +/ 10 20 300 0 0 0      
0 ×/ 100 200 300 4001 1 1 1 1In GNU APL...      0 +/ 9999
And that's why the two results in the prior post differ.
> 


Tried this and I think GNU APL works with vectors of more than one value.
So:

     0+/100 200 300 400                 0+/9 9
0 0 0 0 0                                   0 0 0

This is correct.

     0+/100                                     0+/99
100                                           99

This is not.

I don't quite understand how this syntax is supposed to yield this result, 
as +/ should add all of the values in the left argument together, and 
then the 0 wouldn't have much use.
Apparently it works though. I also tried it with variables and 
multiple-depth vectors:

     X←99
     0+/X
99
     Y←X X
     0+/Y
0 0 0
     0+/ ¨ Y
99 99
     
     X←9 9
     0+/X
0 0 0
     Y←X X
     0+/Y
0 0   0 0   0 0
     0+/ ¨ Y
0 0 0   0 0 0

This all coincides with the same operation without vars or 
multiple-depth vectors.

Best regards,
Louis