C ++比较值与给定的值 [英] C++ comparing bunch of values with a given one

问题描述

我需要将一个给定的值与检索到的值进行比较。我在代码中做了几次。我不满意它的外观，我正在寻找一种util函数。任何人都写了一个？

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 function. Anyone wrote one?

我比较的值的数量在编译时是已知的。

Number of values I am comparing with is known at the compile time.

更新： / strong>我想摆脱容器，因为我知道确切的值的数量（通常不超过3）我想比较。每次将项目放到容器中并不是那么方便。

我不喜欢如果，因为它不像find那么明显。

Update: I'd like to get rid of containers as I know exact amount of values ( often not more then 3 ) I want to compare with. And it is not so convenient to put items to the container every time.
I don't love if neither because it is not obvious as "find".

#include <algorithm>
#include <string>
#include <vector>

std::string getValue1()
{
    return "test";
}

std::string getValue2()
{
    return "the";
}

std::string getValue3()
{
    return "world";
}

int main()
{
    const std::string value = "the";

    // simple if
    if ( value == getValue1() ||
         value == getValue2() ||
         value == getValue3() )
        return 1;

    // using collections like vector, set
    std::vector<std::string> values;
    values.push_back( getValue1() );
    values.push_back( getValue2() );
    values.push_back( getValue3() );
    if ( values.end() != std::find( values.begin(), values.end(), value ) )
        return 1;

    // third option I'd use instead
    //

    return 0;
}

推荐答案

/ p>

For your request to do

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

尝试这样：

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

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

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

此语法可能更清楚：

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

template <typename T, typename U, typename V>
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 <typename W>
    bool Contains(const W &v) const
    {
        return V1 == v || V2 == v || V3 == v;
    }
};

template <typename T, typename U>
class Set2 
{ 
     // as above 
};

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

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

如果这些值真的是树或链表的一部分，你的集合/容器已经，你最好的打赌是只使用一些递归：

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);

您只需将此添加到父类和子类都属于的任何类：

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));
    }
};

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