Re: clearing intermediate variables at end of functions?

[Daniel J Sebald]

On 08/29/2014 11:35 AM, Rik wrote:
> 8/29/14
>
> All,
>
> I was just cleaning up nchoosek.m and I came across this construct at the
> end of the function:
>
> --- Begin Code ---
>      clear cA b;
>      C = C.';
>    endif
>
> endfunction
> --- End Code ---
>
> Is there any reason why it should be necessary to clear the intermediate
> variables cA and b manually?  They are local to the m-file and as soon as
> the endfunction is hit they will go out of scope and the memory should be
> reclaimed.  I thought maybe, just maybe, it was because they were large and
> the original programmer was worried that the transpose operation was going
> to create an intermediate copy of C.  But this shouldn't be the case,
> should it?  Don't we do something intelligent like simply reverse the row,
> column attributes on the existing C matrix rather than creating a full
> blown copy?

Yes, I think so.  That clearing of local variables inside a function 
looks like it is cruft.


The following error statement doesn't exactly match what all those 
conditionals are doing:

    error ("nchoosek: args are non-negative integers with V not less 
than K");

There is also a test in there for non-integers, for which this algorithm 
doesn't apply as stated in the documentation.


The following warning call doesn't appear to be the correct format:

      warning ("nchoosek", "nchoosek: possible loss of precision");

It just returns "warning: nchoosek":

octave-cli:4> nchoosek(500,300)
warning: nchoosek
ans =   5.0549e+144


I'm not sure the conformity of the output makes sense in terms of k and 
size of v, i.e., all these different scenarios.  Let me know when you 
are done editing this file, and I'll have another look.

Dan