 C#快餐－12
发信人: nice (春天), 信区: DotNET
标 题: C#快餐－12
发信站: BBS 水木清华站 (Thu Jul 26 02:15:54 2001)
Lesson 12. Delegates.
Let's consider a problem of calculating a numerical integral. We would like
to have a method which takes different functions and outputs corresponding
values of the integral of these functions. In C++ the code would look like
this:
#include<iostream>
using namespace std;
//calculate the integral of f(x) between x=a and x=b by splitting the interv
al in step_number steps
double integral(double (*f)(double x),double a, double b,int step_number)
{
double sum=0;
double step_size=(b-a)/step_number;
for(int i=1;i<=step_number;i++)
sum=sum+f(a+i*step_size)*step_size; //divide the area under f(x) into st
ep_number rectangles and sum their areas
return sum;
}
//simple functions to be integrated
double f1( double x)
{
return x*x;
}
double f2(double x)
{
return x*x*x;
}
void main()
{//output the value of the integral.
cout<<integral(f1,1,10,20)<<endl;
}
How would we do the same thing in C#? The code bellow is almost exactly the
same. The main difference is that method integral takes a delegate instead
of a pointer to a function. An instance of a delegate new Integral.
Function(f1) must be passed to the method integral.
using System;
//calculate the integral of f(x) between x=a and x=b by splitting the interv
al in step_number steps
class Integral
{
public delegate double Function(double x); //declare a delegate that tak
es a double and returns a double
public static double integral(Function f,double a, double b,int step_num
ber)
{
double sum=0;
double step_size=(b-a)/step_number;
for(int i=1;i<=step_number;i++)
sum=sum+f(a+i*step_size)*step_size; //divide the area under f(x) int
o step_number rectangles and sum their areas
return sum;
}
}
class Test
{
//simple functions to be integrated
public static double f1( double x)
{
return x*x;
}
public static double f2(double x)
{
return x*x*x;
}
public static void Main()
{//output the value of the integral.
Console.WriteLine(Integral.integral(new Integral.Function(f1),1,10,20));
}
}
--
※ 修改:·walts 於 Jul 26 10:29:00 修改本文·[FROM: 166.111.142.118]
※ 来源:·BBS 水木清华站 smth.org·[FROM: 166.111.176.234]
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