理解Lambda表达式和闭包

了解由函数指针到Lambda表达式的演化过程

Lambda表达式的这种简洁的语法并不是什么古老的秘法,因为它并不难以理解(难以理解的代码只有一个目的,那就是吓唬程序员)

#include "stdafx.h"
using namespace System;

typedef void(*FunctionPointer)(System::String ^str);

void HelloWorld(System::String ^str)
{
    Console::WriteLine(str);
    Console::ReadLine();
}

int main(array<System::String ^> ^args)
{
    FunctionPointer fp = HelloWorld;
    fp("Hello World");
    return 0;
}

using System;
using System.Collections.Generic;
using System.Text;

namespace CharpFunctionPointer {
    class Program {

        delegate void FunctionPointer(string str);

        static void Main(string[] args) {
            FunctionPointer fp = HelloWorld;
            fp("Hello World!");
        }

        static void HelloWorld(string str) {
            Console.WriteLine(str);
            Console.ReadLine();
        }
    }

}

using System;
using System.Collections.Generic;
using System.Text;

namespace CharpFunctionPointer {
    class Program {

        delegate void FunctionPointer(string str);

        static void Main(string[] args) {
            FunctionPointer fp = delegate (string s) {
                Console.WriteLine(s);
                Console.ReadLine();
            };
            fp("Hello World!");
        }
    }

}

using System;
using System.Collections.Generic;
using System.Text;

namespace CharpFunctionPointer {
    class Program {

        delegate void FunctionPointer(string str);

        static void Main(string[] args) {
            FunctionPointer fp =
                s => Console.WriteLine(s);

            fp("Hello World!");
            Console.ReadLine();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Text;

namespace CharpFunctionPointer {
    class Program {

        static void Main(string[] args) {
            Action<string> fp = s => Console.WriteLine(s);

            fp("Hello World!");
            Console.ReadLine();
        }
    }
}

Lambda表达式和闭包

using System;
using System.Collections.Generic;
using System.Text;
using System.Linq;

namespace LambdaClosure {
    class Program {

        static void Main(string[] args) {
            UsesClosure();
        }

        static void UsesClosure() {
            string toFind = "ed";
            var words = new string[] {
                "ended","friend","closed","potato"
            };

            var matches = words.Select(s => s.Contains(toFind));
            foreach(var str in matches) {
                Console.WriteLine(str);
            }
            Console.ReadLine();
        }
    }
}

柯里化(Currying)

using System;
using System.Collections.Generic;
using System.Text;
using System.Linq;

namespace LambdaCurry {
    class Program {

        static void Main(string[] args) {
            Func<int,int,int> longLambda = (x,y) => x + y;
            Console.WriteLine(longLambda(3,4));

            //currying
            Func<int,Func<int,int>> curry = x => y => x + y;
            Console.WriteLine(curry(3)(4));

            Console.ReadLine();
        }
    }
}