Question

我想知道的是如何将字符串转换为运算符。

我希望能够将一个值与另一个值进行比较，并且它是否为真的条件是字符串。例如，字符串可能是'＆gt;'或'＆gt; ='或其他我可以定义为'GREATER_THAN'的东西。

最佳方式只是一个案例，还是有更好的使用C＃的wizadry？

Answer 1

您可以使用以下简单方法：

private bool Compare(string operator, int x, int y)
{
    switch (operator)
    {
        case ">": return x > y;
        case "<": return x < y;
        case "==": return x == y;
        ... etc.            
    }
}

bool result = Compare(">", 6, 8);

Answer 2

这样的事情（让我们概括一下解决方案）：

ini_set('display_errors', 1);
foreach ($showAll as $client)
{
    $data_array[] = array(
                'name' => $client['name'],
                'value' => $client['name'],
                'text' => $client['name']
    );
}
// add these lines to your code.
$result=array();
$result["success"]=true;
$result["results"]=$data_array;
echo json_encode($result);

样品：

private static bool MyCompare<T>(string comparer, T x, T y) where T: IComparable<T> {
  // we can't put x.CompareTo(y) since either x or y or both can be null 
  int v = Comparer<T>.Default.Compare(x, y);

  //TODO: you may want strict tests: if (comparer == ">") return v == 0; else if () ... 
  if (comparer.Contains('<') && v < 0)
    return true;

  if (comparer.Contains('>') && v > 0)
    return true;

  if (comparer.Contains('=') && v == 0)
    return true;

  if (comparer.Contains('!') && v != 0)
     return true;

  return false;
}

Answer 3

不能定义新的运算符，但是如果要为自己的新业务对象定义比较，则可以为模型的用户运算符重载。在这里找到如何做到这一点

https://www.tutorialspoint.com/csharp/csharp_operator_overloading.htm

using System;
namespace OperatorOvlApplication
{
   class Box
   {
      private double length;    // Length of a box
      private double breadth;   // Breadth of a box
      private double height;    // Height of a box

      public double getVolume()
      {
         return length * breadth * height;
      }

      public void setLength( double len )
      {
         length = len;
      }

      public void setBreadth( double bre )
      {
         breadth = bre;
      }


      public void setHeight( double hei )
      {
         height = hei;
      }

      // Overload + operator to add two Box objects.
      public static Box operator+ (Box b, Box c)
      {
         Box box = new Box();
         box.length = b.length + c.length;
         box.breadth = b.breadth + c.breadth;
         box.height = b.height + c.height;
         return box;
      }

      public static bool operator == (Box lhs, Box rhs)
      {
         bool status = false;
         if (lhs.length == rhs.length && lhs.height == rhs.height && lhs.breadth == rhs.breadth)
         {
            status = true;
         }
         return status;
      }

      public static bool operator !=(Box lhs, Box rhs)
      {
         bool status = false;
         if (lhs.length != rhs.length || lhs.height != rhs.height || lhs.breadth != rhs.breadth)
         {
            status = true;
         }
         return status;
      }

      public static bool operator <(Box lhs, Box rhs)
      {
         bool status = false;
         if (lhs.length < rhs.length && lhs.height < rhs.height && lhs.breadth < rhs.breadth)
         {
            status = true;
         }
         return status;
      }

      public static bool operator >(Box lhs, Box rhs)
      {
         bool status = false;
         if (lhs.length > rhs.length && lhs.height > rhs.height && lhs.breadth > rhs.breadth)
         {
            status = true;
         }
         return status;
      }

      public static bool operator <=(Box lhs, Box rhs)
      {
         bool status = false;
         if (lhs.length <= rhs.length && lhs.height <= rhs.height && lhs.breadth <= rhs.breadth)
         {
            status = true;
         }
         return status;
      }

      public static bool operator >=(Box lhs, Box rhs)
      {
         bool status = false;
         if (lhs.length >= rhs.length && lhs.height >= rhs.height && lhs.breadth >= rhs.breadth)
         {
            status = true;
         }
         return status;
      }
      public override string ToString()
      {
         return String.Format("({0}, {1}, {2})", length, breadth, height);
      }
   }

   class Tester
   {
      static void Main(string[] args)
      {
         Box Box1 = new Box();   // Declare Box1 of type Box
         Box Box2 = new Box();   // Declare Box2 of type Box
         Box Box3 = new Box();   // Declare Box3 of type Box
         Box Box4 = new Box();
         double volume = 0.0;    // Store the volume of a box here

         // box 1 specification
         Box1.setLength(6.0);
         Box1.setBreadth(7.0);
         Box1.setHeight(5.0);

         // box 2 specification
         Box2.setLength(12.0);
         Box2.setBreadth(13.0);
         Box2.setHeight(10.0);

         //displaying the Boxes using the overloaded ToString():
         Console.WriteLine("Box 1: {0}", Box1.ToString());
         Console.WriteLine("Box 2: {0}", Box2.ToString());

         // volume of box 1
         volume = Box1.getVolume();
         Console.WriteLine("Volume of Box1 : {0}", volume);

         // volume of box 2
         volume = Box2.getVolume();
         Console.WriteLine("Volume of Box2 : {0}", volume);

         // Add two object as follows:
         Box3 = Box1 + Box2;
         Console.WriteLine("Box 3: {0}", Box3.ToString());

         // volume of box 3
         volume = Box3.getVolume();
         Console.WriteLine("Volume of Box3 : {0}", volume);

         //comparing the boxes
         if (Box1 > Box2)
            Console.WriteLine("Box1 is greater than Box2");
         else
            Console.WriteLine("Box1 is  greater than Box2");

         if (Box1 < Box2)
            Console.WriteLine("Box1 is less than Box2");
         else
            Console.WriteLine("Box1 is not less than Box2");

         if (Box1 >= Box2)
            Console.WriteLine("Box1 is greater or equal to Box2");
         else
            Console.WriteLine("Box1 is not greater or equal to Box2");

         if (Box1 <= Box2)
            Console.WriteLine("Box1 is less or equal to Box2");
         else
            Console.WriteLine("Box1 is not less or equal to Box2");

         if (Box1 != Box2)
            Console.WriteLine("Box1 is not equal to Box2");
         else
            Console.WriteLine("Box1 is not greater or equal to Box2");
         Box4 = Box3;

         if (Box3 == Box4)
            Console.WriteLine("Box3 is equal to Box4");
         else
            Console.WriteLine("Box3 is not equal to Box4");

         Console.ReadKey();
      }
   }
}

否则，您可以编写一个比较函数，该函数将为您提供自定义运算符名称和操作数

将字符串转换为运算符

3 个答案: