Ric wrote:
> 10&#.^:_1 (or 10&#.inv ) has always seemed to me to be the "right"
> way of converting a number to its digits but it is slower and fatter than
> the other methods:
Pepe wrote:
> Perhaps, for the reason that you mentioned, there is case for
> special code for ( 10&#.^:_1 ) .
Agreed. This has bothered me before, but then I'm more of purist and less
pragmatist when it comes to J. I imagine many people are
satisfied with the special code supporting "."0@": [1].
> ( ,.&.": ) is indeed a neat phrase
Also agreed! However, I am concerned with (&.":), because it applies
(":^:_1), which is (". ) which obviously can and will
execute arbitrary code. And this implication may not be obvious to the
programmer when he types (&.":). Now, there's no problem
if he controls (y) but applying these phrases to user strings makes the
application vulnerable to "J injection" attacks.
This isn't a problem in the current case (because the input is numeric, and
even if it were a rank-1 string, (".) would never be
applied to more than one character anyway). But I do have an open relevant
enhancement request open on it [2], where I recommend
x&". be made invertible.
-Dan
[1] http://www.jsoftware.com/help/release/digits10.htm
[2]
http://www.jsoftware.com/jwiki/System/Interpreter/Requests#makedyad.22.invertible
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