Yesterday I stumbled over a surprising behaviour of Array's sort, which led me
to open a bug report
<https://sourceforge.net/p/oorexx/bugs/1107/>. Obviously the sorting is working
as designed, hence
the reported behaviour was not accepted as a bug.
Having slept a night over this and thinking about my utmost surprise that sort
would raise an error
condition if it hits an empty array element (one without an entry) in between,
I try to summarize my
thoughts about the current behaviour, requesting a change of the design and
implementation to get
rid of the surprising factor and to remove undeterminable fragility from the
Array sort.
First, the current design and implementation:
The single dimiensioned array that gets sorted must not have empty entries
in between. If the
sort tries to refer to an empty slot it raises "Error 98.975: Missing array
element at position
xyz" and the program is ended, if the condition does not get trapped.
Thoughts about this:
1. Having worked for many years sorting arrays, I was *totally surprised*
about this unexpected
(because never experienced) behaviour! The surprise factor for me was at
the maximum.
2. There is no documentation going with sorting arrays that would communicate
that the arrays to be
sorted must have no empty elements in between that I am aware of. Therefore
one cannot expect
this behaviour at all.
3. If one uses single dimensioned arrays that get changed in routines and
methods (written by
others) such that elements get removed in between, then sorting such an
array all of a sudden
(and totally unforseeable) raises the above mentioned error condition,
which makes sort quite
fragile for programmers IMHO.
1. To overcome this situation, one must advice every ooRexx programmer to
do *always* a
(potentially time-consuming) makearray before sorting an array just to
make sure that the
aforementioned error condition does not get raised.
4. Finally, I would have expected that an array with empty elements should be
sortable without a
problem, therefore my utmost surprise! :)
1. My expectations would be simply as follows: if a single dimensioned
array contained empty
elements, then sorting would work and all the empty elements are sorted
to the end of the
array, no matter what the comparison method returns. This way, after a
sort, all empty
elements are always at the end of the array. (The items and size
messages would remain the
same.)
The questions I would have, before contemplating about filing a RFE:
* am I the only one who is surprised about a failing sort on a single
dimensioned array if in
between there are empty elements?
* Independent of this, would it be acceptable to change the current design
and implementation of
the sort such that empty elements are tolerated and put to the end of the
array (what would be
arguments, thoughts that speak against such a change)?
---rony
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