[Haskell-cafe] Annotating calculations

Sam Mason sam at samason.me.uk
Wed Jun 15 14:21:23 EDT 2005

Rene de Visser wrote:
>Designing the data structures to store the calculation results seems to be 
>non-trivial, so I guess I should do this first.

I think that part of the problem is that when you need to be able
to reference results from the inside of a calculation (or any sort
of expression) you need to be able to refer to them somehow.  One
of the easier ways of doing this would be to bung them into some
sort of data structure, alternatives would be to use a spreadsheet
type abstraction that allows you to pull things out.  Someone posted
a reference to an interesting paper that you may be able to build


It's probably not going to be a trivial translation, but once you've
written your calculations in this style, you should be able to get at
out the intermediate values easily.  At least I wrote something
similar in Java a few years ago that did similar things, and it was
quite a nice of abstraction to work with.

I guess it's not going to matter much for you, but the problem of
using some specific data structure is that it's probably going to
be very closely related to the structure of the code.  If you need
to change the code in any non-trivial way the data structure is
going to have to change and all of the code that deals with the
data structure will as well.  Because your report is probably going
to have to change in sync with the calcs this probably isn't going
to be much of a problem, but in other situations it can be a bit
of a pain.

>Then maybe the solution to the other 
>problem will be apparent.

I think your main problem is that you need some way of labeling the
intermediate results so you can refer to them later when you need
them in the report.  One you've worked out how you're going to do
that, everything else should fall into place.

Hope that helps!


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