C++ comparing bunch of values with a given one

Question

I need to compare one given value with a retrieved values. I do this several times in the code. I am not satisfied with how it looks and I am seeking for a some sort of an util

Answer 1

For your request to do

if (InSet(value)(GetValue1(), GetValue2(), GetValue3()))
{
   // Do something here...
}

Try this:

template 
class InSetHelper
{
     const T &Value;
     void operator=(const InSetHelper &);
public:
     InSetHelper(const T &value) : Value(value) {}

     template
     bool operator()(const Other &value1, const Another &value2) const
     {
         return Value == value1 || Value == value2;
     }
     template
     bool operator()(const Other &value1, const Another &value2, const AThird &value3) const
     {
         return Value == value1 || Value == value2 || Value == value3;
     }
};

template  
InSetHelper InSet(const T &value) { return InSetHelper(value); }

This syntax might be more clear though:

if (MakeSet(GetValue1(), GetValue2(), GetValue3()).Contains(value))
{
   // Do something here...
}

template 
class Set3
{
    const T& V1;
    const U& V2;
    const V& V3;
    void operator=(const Set3 &);
public:
    Set3(const T &v1, const U &v2, const V &v3) : V1(v1), V2(v2), V3(v3) {}

    template 
    bool Contains(const W &v) const
    {
        return V1 == v || V2 == v || V3 == v;
    }
};

template 
class Set2 
{ 
     // as above 
};

template 
Set3 MakeSet(const T &v1, const U &v2, const V &v3)
{
    return Set3(v1, v2, v3);
}

template 
Set3 MakeSet(const T &v1, const U &v23)
{
    return Set3(v1, v2);
}

If those values are really part of a tree or a linked list, then you have your set/container already, and your best bet is to just use some recursion:

parent.ThisOrDescendantHasValue(value);

You'd just add this to whatever class parent and child belong to:

class Node
{
public: 
    Value GetValue();
    Node *GetChild();
    bool ThisOrDescendantHasValue(const Value &value)
    {
        return GetValue() == value
           || (GetChild() && GetChild->ThisOrDescendantHasValue(value));
    }
};