Chris Rathman wrote:
I appreciate the help I've gotten and hope not to wear out my welcome,
but I'm stuck again. This is probably not the sort of problem for a Oz
newbie like myself to tackle, but it's the one in my path at the
moment. Not sure I can clearly state the problem, but here goes....
If I have an unbound variable (Z) in the last position of a list like say:
X|Y|Z
Then the structure of the variable Z in the tail could theoretically be
any of the following possibilities along an infinite choice of
possibilities:
A|B|C|Z = _|_|_|nil %% Z = nil
A|B|C|Z = _|_|_|_|nil %% Z = _|nil
A|B|C|Z = _|_|_|_|_|nil %% Z = _|_|nil
.... %% Z = _|_|...|nil
And so on. What I'd like is to have a function that generates the
possible choices of the infinite variety of structures that are possible
when an unbound variable is in the last position of the list.
You can write a predicate (procedure) IsList that enforces its argument
to be a list:
proc {IsList X}
choice
X=nil
[] T in X=_|T {IsListT}
end
end
Does this fit your needs?
Cheers,
raph
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