Re: [Cobolforgcc-devel] MOVE within UNSTRING

[Tim J. <te...@me...>]

Steven,

I tend to think the best way might be to do it in a quite simple manner
ie with the inner loops. Most unstrings I have seen have only had one or
a small number of short delimiters. The Extreme Programming term for this
is 'The Simplest Thing That Could Possibly Work'.

As far as the data types go, the receiving area must be display but can
be numeric (with all the usual overpunching stuff) and can be right
justified as well as left justified.

The core compiler does not support numeric display or right justified
yet, so support for these is not urgent and there is no runtime routine
to do it yet. My thought would be to support right justified in your own
code. When I add right justified to the compiler I will pull that code
out into its own routine. But I would just put an abort in if you get a
numeric display format output item. We could add that support later on
quite easily, as a call to the appropriate move routine.

My preference always is to get something working and then refine it,
rather than solve all the problems at once. But go with the approach you
are most comfortable with.

Tim Josling

"Steven O. Ellis" wrote:

> Tim,
>
> I set up several designs for test cases and coded a few of them.
> Then I decided to go back and actually start coding the UNSTRING
> routine.  Whew!  Nontrivial.
>
> The problem lies in preventing excessive looping when the user
> (COBOL programmer) specifies several, long delimiters.  There is
> a risk of having to set up the problem all over again, one byte at a
> time, when several delimiters are matching up to a point and then
> failing, causing the algorithm has to have to backtrack over and over.
>
> In order to handle this, I am exploring the Knuth-Morris-Pratt
> algorithm as discussed in "Introduction to Algorithms", by
> Cormen, Leiserson, and Rivest (c) 1990 MIT.  I have this coded
> but not yet tested.  A slight modification to the KMP algorithm
> would seem to allow the delimiter-check to ride along the source
> field in a linear fashion, without backtracking, even with multiple
> length delimiters.
>
> This brings up a few questions.   I have no compiler-writing
> training, and I'm  not familiar with your overall design, so perhaps
> we can discuss this.
>
> We talked about MOVE awhile back but I don't think I ever
> directly asked this: can UNSTRING call the
> MOVE routine, or must it be coded within UNSTRING itself?  If
> MOVE has been coded and is available, I would like to have the
> source and headers.  If not coded but the call is OK, I will put in
> a temporary function.  If the call is not OK, I will code the move
> into the UNSTRING function itself.
>
> Speaking of function calls, is UNSTRING allowed to call another
> function at all?  The KMP algorithm is best implemented as two
> functions.  One I am coding into UNSTRING itself, but the initial
> setup should be done by a function called by UNSTRING.
> Is this OK?
>
> If it is OK to use a separate function for setting up the algorithm,
> then I have another question about how the compiler deals with
> this, but I'll wait until I hear back from you.
>
> Steven
>
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