[AccessD] Swap two elements in an array

[John Colby]

And now that you rolled your own, make it a function called swap.  Feed in
the array and indexes and bob's your aunt.

On Thu, Aug 18, 2022 at 5:27 PM Paul Wolstenholme <
Paul.W at industrialcontrol.co.nz> wrote:

> There are answers that work without a temporary variable in some
> circumstances.  I've used those in the world of programming small
> microprocessors but I don't think they are likely to be your best solution
> here.
>
> The following sequence generally works on small microprocessor compilers
> but I've never tried it in VBA:
> A = A XOR B
> B = A XOR B
> A = A XOR B
>
> The following should also work on integer types (floating point can have
> rounding errors) IF any overflow is not trapped and it results in rollover
> (or alternatively if there is no overflow):
> A = A + B
> B = A - B
> A = A - B
>
> I think the temporary variable is preferable.
>
> When you talk about 'the best way' that could involve using pointers to the
> array elements so the compiler evaluates the memory locations once.  You
> might want speed or you might want simplicity.
>
> Paul Wolstenholme
>
>
> On Fri, 19 Aug 2022 at 04:16, Arthur Fuller <fuller.artful at gmail.com>
> wrote:
>
> > Thanks, Stuart.
> >
> > After sending my message, I rolled my own, using exactly the same
> technique
> > as you -- couldn't think of a way around the temp variable.
> >
> > On Thu, Aug 18, 2022 at 9:41 AM Stuart McLachlan <stuart at lexacorp.com.pg
> >
> > wrote:
> >
> > > Since VBA doesn't have a SWAP function, you have to do it with a
> > temporary
> > > variable
> > > Assuming it's a one dimensional array, something like:
> > >
> > > Temp = Arr(2) : Arr(2) = Arr(4) : Arr(4) = Temp
> > > If you define Temp as a Variant, you can use it with any type of array.
> > >
> > > If it's a multi-dimensional array, you have to sway each dimension:
> > > Temp = Arr(1,2) : Arr(1,2) = Arr(1,4) : Arr(1,4) = Temp
> > > Temp = Arr(2,2) : Arr(2,2) = Arr(2,4) : Arr(2,4) = Temp
> > > Temp = Arr(3,2) : Arr(3,2) = Arr(3,4) : Arr(3,4) = Temp
> > > ...
> > >
> > >
> > > On 18 Aug 2022 at 8:35, Arthur Fuller wrote:
> > >
> > > > What is the best way to swap two elements in an array? Typically they
> > > > are adjacent but ideally I want a method that can swap any two
> > > > elements.
> > > >
> > > > --
> > > > Arthur
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> > >
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> > Arthur
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-- 
John W. Colby
Colby Consulting