BacktraQ is a framework for running Prolog-like queries with backtracking, choicepoints & variable unification within managed C#.
The library has no external dependencies and runs as pure managed code, to allow it to be used in limited/sandbox domains like Unity3D.
BacktraQ has two stages - building queries, and running them. Building queries is designed to look like a native extension to C# syntax, so logic program code is inline with regular imperative statements. Various operators have been overloaded to support this - for example, <= is used as the unification operator.
// Create unbound variables
var a = new Var<int>();
var b = new Var<int>();
// Create query as "unify a with b, and unify b with 123"
var query = a <= b & b <= 123;The query doesn't execute and no variables are set/unified until you test for success:
if (query.Succeeds())
{
Console.WriteLine($"a = {a}");
Console.WriteLine($"b = {b}");
}If a query may have multiple solutions, it can be iterated over and the value of each variable will update:
// Create unbound variable
var a = new Var<int>();
// Create query as "unify a with 'a', or 'b', or 'c'"
var query = a <= 'a' | a <= 'b' | a <= 'c';
foreach (var result in query)
{
Console.WriteLine($"a = {a}");
}Pull requests are welcome!