differential.h

常微分方程数值解法

#ifndef Differential_h
#define Differential_h
#include<iostream.h>
#include<math.h>
#include<stdlib.h>
#include<iomanip.h>
#include<fstream.h>
#define filename "initial.txt"
#define E 1.0e-8
double fabs(double x,double y){
	double temp=x-y;
	if(temp>=0)return temp;
		else return -temp;
}
template<class Type> class Differential{
protected:
	Type low,high,h,H,*u0,*t;int k,n,N;
    Type (*u)(Type);
    Type (*f)(Type,Type);
public:
	Differential(Type (*pf)(Type,Type));
	~Differential(){delete []u0;delete []t;}
	Type U(Type t,Type (*u)(Type));
	Type F(Type t,Type u,Type (*f)(Type,Type));
	void Exact();//precision;
};
template<class Type> Differential<Type>::Differential(Type (*pf)(Type,Type)){
	f=pf;
    ifstream fin(filename,ios::in|ios::nocreate);
	cout<<"Input low:";fin>>low;	
	cout<<"Input high:";fin>>high;
	cout<<"Input h:";fin>>h;
	fin.close();
	H=high-low;N=int(H/h);
	u0=new Type[N+1];
	t=new Type[N+1];
	for(int i=0;i<N+1;i++)
	t[i]=low+i*h;
}
template<class Type> Type Differential<Type>::U(Type t,Type (*u)(Type)){//
	return u(t);
}
template<class Type> Type Differential<Type>::F(Type t,Type u,Type (*f)(Type,Type)){//
	return f(t,u);
}
template<class Type> void Differential<Type>::Exact(){
	for(int i=0;i<N+1;i++)
	{u0[i]=U(t[i],u);}
}
#endif