以前在MCD上听说过,又见过几个讨论,忘了在哪里,也没弄清楚怎么实现的,今天中午试了一下,居然成功了,高兴ing!贴出来,与大家分享:
(VS.NET 2005)
template<long M,long N>struct CanDivid //whether N can be divided by (2 to M)
{
enum{Result = (N % M == 0 || CanDivid<M - 1,N>::Result)};
};
template<long N>struct CanDivid<2,N>
{
enum{Result = (N % 2 == 0)};
};
template<long N>struct CanDivid<1,N>
{
enum{Result = 0};
};
template<long N>struct CanDivid<0,N>
{
enum{Result = 0};
};
template<long N>struct Prime
{ //whether N is a prime number
enum{IsPrime = !CanDivid<N / 2,N>::Result};
Prime();
};
template<bool R,class T1,class T2>struct Selector //type selector
{
typedef T1 RType;
};
template<class T1,class T2>struct Selector<false,T1,T2>
{
typedef T2 RType;
};
template<long N>struct Generate:public Generate<N-1>
{
typedef typename Selector<Prime<N>::IsPrime,Prime<N>,int>::RType RType;
Generate(){
RType();
}
};
template<>struct Generate<2>
{
Generate(){
Prime<2>();
}
};
int main(){
Generate<100>(); //generate prime numbers from 2 to 100 in Error Message
}
作用:在错误信息里输出100以内的素数。