The rank n in u"n is, in the general case, 3 numbers
monad,dyadl,dyadr
where monad = rank of u"n when used as a monad
dyadl = left rank of u"n when used as a dyad
dyadr = right rank of u"n when used as a dyad
If you give just 2 numbers (l,r), it is handled as if you gave
r,l,r
If you give just 1 number n, it is as if you gave
n,n,n
This is what the Dictionary entry means when it refers to
3 $&.|. n
Henry Rich
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of p j
> Sent: Wednesday, March 15, 2006 9:41 AM
> To: Programming forum
> Subject: [Jprogramming] 3rd parameter to rank
>
> 1 2 3 +"1 0 (4 5)
> 5 6 7
> 6 7 8
>
> If you add a 3rd rank parameter you get.
> 1 2 3 +"1 0 0 (4 5)
> |length error
> 1 2 3 +"1 0 1 (4 5)
> 1 2 3 +"1 0 2 (4 5)
> 1 2 3 +"1 0 _ (4 5)
> 4 5 +"1 0 (1 2 3) NB. All 3 give same result
> 5 6
> 6 7
> 7 8
>
> The 3rd rank parameter to verbs isn't well documented.
> Apparently though, if it is not supplied there is no
> default value. Can you provide or point to an
> explanation of what it does?
>
> Also,
> IndexExcept =: 4 : 'I. x. (i. = [: # [) y.'
>
> ,. (,. (i.6)) IndexExcept"_ 0 _ (i.6)
> ,. (,. (i.6)) IndexExcept"1 0 _ (i.6)
> ,. (,. (i.6)) IndexExcept"1 0 1 (i.6)
> ,. (,. (i.6)) IndexExcept"0 0 1 (i.6)
> 1 2 3 4 5
> 0 2 3 4 5
> 0 1 3 4 5
> 0 1 2 4 5
> 0 1 2 3 5
> 0 1 2 3 4
> ,. (,. (i.6)) IndexExcept"1 0 (i.6)
> ,. (,. (i.6)) IndexExcept"1 0 _1 (i.6)
> (blank output 6 lines)
> NB. All above variations without 3rd rank parameter
> produce same blank output.
>
> Its pretty easy to understand what you are doing to a
> verb with the first 2 rank arguments: Applies verb to
> shape of x and y respectively. The 3rd rank parameter
> has come in handy for me on several occasions, but I
> just randomly added it to a verb operation that was
> giving rank errors or strange results. I still don't
> understand what it does even after studying the above
> behaviour. Is _1 the default 3rd parameter for rank?
>
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