Question

Is there a way to write non-homogenous lists in prolog?
I want to create a list which contains symbols and integers. Something like:
[A 2 3 B C D E]

Thanks

P.S. I user Turbo Prolog 2.0

Answer 1

Turbo Prolog requires that list elements be of a single type. But there is a way around this – you just need to define a single type which can represent both integers and symbols. You can do this by defining a compound domain, in which each different type is wrapped with a different functor. So, for example:

mixed_type = i(integer); s(symbol).
mixed_list = mixed_type*.

The downside is that you need a functor around every list element, which is a bit awkward:

[s(a), i(2), i(3), s(b), s(c)]