private static Stream MakeStream(Substitution curr, DelayedStream getRest)
{
return(new Stream()
{
Curr = curr,
GetRest = getRest
});
}
public static IList <object> Run(int?n, Func <KRunner, FreshVariable, Goal> body)
{
var k = new KRunner();
// 定义待求解的未知量q
var q = k.Fresh();
// 执行body，得到最终目标g
var g = body(k, q);
// 初始上下文是一个空替换，应用到g，得到包含可行替换的Stream s
var s = g(Substitution.Empty());
// 从s中取出前n个（n==null则取所有）替换，查找各个替换下q的解，并给自由变量换个好看的符号。
return(s.MapAndTake(n, sub => Renumber(sub.Walk(q))));
}
public static Stream Unit(Substitution sub)
{
return(MakeStream(sub, () => Empty()));
}
private Substitution(Substitution p, FreshVariable var, object val)
{
parent = p;
Var = var;
Val = val;
}