Re: Decision Tables


"Ben Bacarisse" <ben.usenet@xxxxxxxxx> wrote in message
news:87abmo9n9b.fsf@xxxxxxxxxxxx
"Bartc" <bc@xxxxxxxxxx> writes:

The business part is the half-dozen lines of Match(), which I'd imagine
would not be impossible in C, depending on the actual types of the fields
being tested.

It would not be that hard in C (though a little messy) but see below.

Function Match(A, B, map)=

forall i in map do
if A.[i]<>B.[I] then return 0 fi
end

return 1
End

What you a showing, I think, is a language that can index record
(or structure) members. In the posted C++, this is done by using
pointers to member functions. Both are key to one part of the OP's
problem but neither really gets to the heart of the OP's question --
how to represent (or denote) compound match predicates.

You mean how to specify which fields are to be compared and to what?

What from I could understand, the OP wanted to compare certain fields of
records A and B. A is input data and B is some reference data. In my code
example the fields are specified as a list of field numbers.

Another way was in Malcolm's example to put wildcards into B (or some
indicator to say 'ignore this field').

My example still stands, but Map disappears and the critical code (best read
as pseudo-code) becomes as follows. (My language just happens to have the
..fields attribute). This is a little less efficient however (must look at
all fields of B), but there are other possibilities too.

I don't think the requirements went any deeper than that and to avoid
writing 2**N laborious functions. My point was to show things could be kept
simple without dragging in external libraries.

Function Match(A, B)=
For i:=1 to A.Fields do
if B.[i]<>"*" and A.[i]<>B.[i] then return 0 fi
end
return 1
End

--
Bart


.

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