[Error] template-id 'maxn<>' for 'void maxn(const char**, int)'

守夜人jedi 2023-05-20 18:34:19
#include <iostream>
#include <cstring>
#include <string>
#include <typeinfo>
using namespace std;

template<class T>
T maxn(T* a,int n);

template<> void maxn(const char* s[],int n);

int main()
{
    //    int n6[6]{21,56,89,49,258,41};
    //    double n4[4]{2.1,5.6,8.9,4.9};
    //    auto m=maxn(n6,6);
    //    auto n=maxn(n4,4);
    //    cout<<m<<endl;
    //    cout<<n<<endl;
    const char* words[3]={"one","two","three"};
    //    maxn(words,3);
    return 0;
}

template<> void maxn(const char* s[],int n)
{
	cout<<"ok";
}



template<class T>
T maxn(T* a,int n)
{
	T max=a[0];
	for (int i=1;i<n;i++)
	{
		if (a[i]>max)
		{
			max=a[i];
		}
	}
	return max;
}




我想写一个maxn的显式具体化函数,会传入一个char*数组的名称作为参数,但是我甚至没有调用函数的时候就报了如下错误:

 [Error] template-id 'maxn<>' for 'void maxn(const char**, int)' does not match any template declaration

 [Note] candidate is: 'template<class T> T maxn(T*, int)'

 [Error] template-id 'maxn<>' for 'void maxn(const char**, int)' does not match any template declaration

[Note] candidate is: 'template<class T> T maxn(T*, int)'

劳烦大神指正。

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GreenCppC 2008-8-24 ========================================= // I 类,对象,函数重载 //-------- From C to C++ ------------ // A simple C Program! // convert a string to uppercase! #include #define N 200 int main(){ char ms[N]; int i; printf("Input ms: "); gets(ms); for(i=0;ms[i];i++) if(ms[i]>='a'&&ms[i]<='z') ms[i]-='\x20'; puts(ms); return 0; } /* path d:\wingw\bin gcc abc.c -o abc.exe */ //------------------------------ // A better C Program! #include #define N 200 void strUpper(char *s); void strLower(char *s); int main(){ char ms[N]; printf("Input ms: "); gets(ms); strUpper(ms); puts(ms); strLower(ms); puts(ms); return 0; } void strUpper(char *s) { for(;*s;s++) if(*s>='a'&&*s<='z')*s-='\x20'; } void strLower(char *s) { for(;*s;s++) if(*s>='A'&&*s<='Z')*s+='\x20'; } //------------------------------ // A C++ Program without class and object! #include using namespace std; const int N=200; void strUpper(char *s); void strLower(char *s); int main(){ char ms[N]; cout<<"Input ms: "; cin.getline(ms,N); strUpper(ms); cout<char *s) { for(;*s;s++) if(*s>='a'&&*s<='z')*s-='\x20'; } void strLower(char *s) { for(;*s;s++) if(*s>='A'&&*s<='Z')*s+='\x20'; } //------------------------------ // A C++ Program with class and object! #include using namespace std; const int N=200; class Str{ char s[N]; public: void out(){cout<char *p; for(p=s;*p;p++) if(*p>='a'&&*p<='z')*p-='\x20'; } void Str::lower() { for(char *p=s;*p;p++) if(*p>='A'&&*p<='Z')*p+='\x20'; } // - - - int main(){ Str a; cin>>a.s; //error! a.in(); a.upper(); a.out(); a.lower(); a.out(); return 0; } ========================================= // II. 构造与析构函数 #include #include using namespace std; class child { char name[20]; int age; public: child(); child(char *n,int a); void ask(char *n); void ask(int a); ~child(); }; // --- child::child(){ strcpy(name,"Tomme"); age=3; } // --- child::child(char *name,int age){ strcpy(this->name,name); this->age=age; // this -- address of self object } // --- void child::ask(char *n){ if(!strcmp(name,n)) cout<<"Yes, i am "<int age){ if(this->age==age) cout<<"Yes, i am "<int main(){ child tom,rose("Rosie",4); tom.age=4; // error! tom.ask("tom"); rose.ask("Alice"); tom.ask(2); return 0; } ========================================= // III. 继承 #include #include using namespace std; class child { protected: //note this change! char name[20]; int age; public: child(); child(char *n,int a); void ask(char *n); void ask(int a); }; // --- child::child(){ strcpy(name,"Tomme"); age=3; } // --- child::child(char *n,int a){ strcpy(name,n); age=a; } // --- void child::ask(char *n){ if(!strcmp(name,n)) cout<<"Yes, i am "<int a){ if(a==age) cout<<"Yes, i am "<char book[20]; public: pupil(char *n,int a,char *b); void list(); }; // --- pupil::pupil(char *n,int a,char *b): child(n,a) { strcpy(book,b); } // --- void pupil::list() { cout<int main(){ child tom,rose("Rosie",4); tom.ask("tom"); rose.ask("Alice"); tom.ask(2); pupil green("Green",9,"Nature"); green.ask("Jack"); green.ask(10); green.list(); return 0; } ========================================= // IV. 增加与基类成员函数同名的函数; // 调用基类成员函数;内联函数(in-line) #include #include using namespace std; class child { protected: char name[20]; int age; public: child(); child(char *n,int a); void ask(char *n); void ask(int a); }; // --- child::child(){ strcpy(name,"Tomme"); age=3; } // --- child::child(char *n,int a){ strcpy(name,n); age=a; } // --- void child::ask(char *n){ if(!strcmp(name,n)) cout<<"Yes, i am "<int a){ if(a==age) cout<<"Yes, i am "<char book[20]; public: pupil(char *n,int a,char *b); void ask(char *n){child::ask(n);} // in-line! void ask(int a){child::ask(a);} void ask(); }; // --- pupil::pupil(char *n,int a,char *b): child(n,a) { strcpy(book,b); } // --- void pupil::ask() { cout<int main(){ child tom,rose("Rosie",4); tom.ask("tom"); rose.ask("Alice"); tom.ask(2); pupil green("Green",9,"Nature"); green.ask("Jack"); green.ask(10); green.ask(); return 0; } ===================================== // V. 对象数组 #include using namespace std; class C1{ int a,b; public: C1(int m,int n){a=m;b=n;} int getAdd(){return a+b;} }; int main() {C1 ob[3]={C1(1,2),C1(3,4),C1(5,6)}; int i; for(i=0;i<3;i++) cout << ob[i].getAdd() << " "; // C1 oe[2]; -- Error! means constructor is C1() // -- need reload C1::C1(){ ... } // -- eg, C1::C1(){a=b=0;} return 0; } ========================================= // VI. 指向对象的指针 C1 obA(2,3), *p; p=&obA; cout << p->getAdd(); //------------- C1 ob[3]={C1(1,2),C1(3,4),C1(5,6)}, *q; q=ob; for(int i=0;i<3;i++) {cout << q->getAdd() << " "; q++; } //------------- class C2{ public: int a; C2(int k){a=k*k;} }; // . . . C2 obB(9); int *p; p=&obB.a; // Note! a is public, p to member cout << *p; // 指向派生类的指针 class Base{ public: int a,b; Base(int m,int n){a=m;b=n;} int getAdd(){return a+b;} }; class Derived: public Base{ int c; public: Derived(int x,int y,int z): Base(x,y) {c=z;} float getAve(){return (a+b+c)/3.0F;} }; // ... Base *bp; Derived d(6,7,9); bp=&d; cout << bp->getAdd(); cout << bp->getAve(); // Error! cout << ((Derived *) bp) ->getAve(); ========================================= // VII. 动态分配:new, delete #include #include using namespace std; int main() {int *p; try{ p=new int; } catch(bad_alloc ex){ cout << "New failed!\n"; return -1; } *p=20; cout << "At "< #include using namespace std; int main() {int *p; try{ p=new int[6]; } catch(bad_alloc ex){ cout << "New failed!\n"; return -1; } float ave=0.0F; int i; cout<<"Enter numbers: "; for(i=0;i<6;i++) {cin>>p[i]; ave+= *(p+i); cout<< *(p+i); } ave/=6.0F; cout << "Ave = "<< ave <<"\n"; delete [] p; return 0; } //------------- #include #include #include using namespace std; class Balance{ char name[40]; double curValue; public: Balance(char *n,double v){ strcpy(name,n); curValue=v; } void getValue(char *n,double &v){ strcpy(n,name); v=curValue; } }; int main() { Balance *p; char s[40]; double bal; try{ p=new Balance("Robin Hood",3536.45); } catch(bad_alloc ex){ cout << "New failed!\n"; return -1; } p->getValue(s,bal); cout<'s balance is "< using namespace std; void neg1(int k); void neg2(int *p); void neg3(int &k); int main() { int x=20; neg1(x); neg2(&x); cout << x<< "\n"; neg3(x); cout << x<< "\n"; } // - - - void neg1(int k) { k=-k;} void neg2(int *p) { *p=-*p;} void neg3(int &k) { k=-k; } //------------- #include using namespace std; class C1{ public: int k; void neg(C1 &o){o.k=-o.k;} // -- no temp object created }; int main() { C1 ob; ob.k=20; ob.neg(ob); cout << ob.k <<"\n"; return 0; } //----------------------------------- /* Input a sentence,reverse all the words except other chars, eg: etihw, dna kcalb! => white, and black! NOT: !black and ,white */ #include #include #include #include using namespace std; const int N=200; /* - - - - - - */ class CharStack{ const int StkLen; char *data; int top; public: CharStack(); ~CharStack(){delete []data;} int push(char x) {if(top>=StkLen-1)return -1; // it's full top++; data[top]=x; return 0; } int pop(char &x) {if(top<=-1)return -1; // empty! x= *(data+top); top--; return 0; } }; CharStack::CharStack():StkLen(40) {try{ data=new char[StkLen]; }catch(bad_alloc){cout<<"New failed!"; exit(-1);} top=-1; } // --------- class WordRev{ char ms[N]; public: void reads() { cout<<"Input str:\n"; cin.getline(ms,N); } void prints() { cout<CharStack stk; int i=0,wStart,wEnd; while(ms[i]) {if(!isalpha(ms[i]))i++; else {wStart=i; while(isalpha(ms[i]))stk.push(ms[i++]); wEnd=i; i=wStart; while(!stk.pop(ms[i]))i++; i=wEnd; } } } // --------- int main() { WordRev sr; sr.reads(); sr.wRev(); sr.prints(); return 0; } ========================================= // IX 函数形参使用默认值 #include #include using namespace std; // ----------- class pupil{ public: char name[20]; int age; char book[20]; pupil(char *n,int a,char *b); void list(); }; // --- pupil::pupil(char *n,int a,char *b){ strcpy(name,n); age=a; strcpy(book,b); } // --- void pupil::list() { cout<char *book="Math"); //---------- int main(){ pupil green("Green",9,"Chinese"); green.list(); nextYear(green); green.list(); nextYear(green,"Nature"); green.list(); return 0; } //---------- void nextYear(pupil &c,char *book="Math") { // ="Math" Should be omitted, for previous prototype c.age++; strcpy(c.book,book); return; } /* D:\green>g++ pupil.cpp -o pupil.exe pupil.cpp: In function `void nextYear(pupil&, char*)': pupil.cpp:41: error: default argument given for parameter 2 of `void nextYear(pupil&, char*)' pupil.cpp:25: error: after previous specification in `void nextYear(pupil&, char*)' */ ========================================= // X. 虚函数 virtual #include using namespace std; class base{ public: virtual void vf(){cout<<"base's vf.\n";} }; class derived1:public base{ public: virtual void vf(){cout<<"derived1's vf.\n";} }; class derived2:public base{ public: virtual void vf(){cout<<"derived2's vf.\n";} }; void f(base &r){r.vf();} int main() {base b, *p; derived1 d1; derived2 d2; b.vf(); d1.vf(); d2.vf(); p=&b; p->vf(); p=&d1; p->vf(); // derived1's vf. p=&d2; p->vf(); // derived2's vf. f(b); f(d1); // derived1's vf. f(d2); // derived2's vf. return 0; } ========================================= // XI. 对象赋值问题 #include #include #include using namespace std; class Myclass{ int *p; public: Myclass(int i); void show(){cout<< *p<<"\n";} ~Myclass(){delete p;} }; Myclass::Myclass(int i){ try{ p=new int; } catch(bad_alloc e) {cout<< "New failed!\n"; exit(-1); } *p=i; } int main() {Myclass a(20); Myclass b=a; //copy by bits b.show(); return 0; // 错误!对象中 p 所指向的内存空间将被释放 2 次! } ========================================= // XII. 拷贝构造函数 ---- 解决对象参数传递的副作用问题 #include #include using namespace std; class array{ public: int *p; int size; array( ){p=NULL;size=0; }; array(int sz); array(const array &a); ~array(){if(!p){delete [ ]p; size=0;}} void input(); }; array::array(int sz){ size=sz; try{ p=new int[size]; }catch (bad_alloc xa){ cout <<"Alloc failed!"; exit(EXIT_FAILURE); } } array::array(const array &a){ try{ p=new int[a.size]; }catch (bad_alloc xa){ cout <<"Alloc failed!"; exit(EXIT_FAILURE); } size=a.size; for(int i=0;iintegers: "; for(int i=0;i>p[i]; } void inc(array a){ int i; for(i=0;i' '; cout<<"\n"; } int main(){ array a(4),c; a.input(); array b(a); // 调用拷贝构造函数 inc(b); //调用拷贝构造函数(隐式) for(int i=0;i' '; return 0; } ========================================= // XIII. 运算符重载 #include using namespace std; class loc{ int longitude,latitude; public: loc(){} //needed to construct temp objects loc(int lg,int lt){longitude=lg; latitude=lt;} void show(){cout<int main() {loc ob1(10,20),ob2(5,30),ob3; ob3=ob1+ob2; ++ob3; ob3.show(); ob1+=ob2; ob1=ob1+ob2; // ob1.+(ob2) like (ob1+ob2).show(); ++ob1; ob1=ob2=ob3; ... ... } ========================================= // XIV. 异常的抛出,捕获与处理 #include using namespace std; int main() {cout <<"Start\n"; try { cout << "Inside try block\n"; throw 100; cout << "This will not execute"; } catch (int i) { cout << "Caught an exception, value is: "; cout << i <<"\n"; } cout << "End\n"; return 0; } // -------------------- #include using namespace std; void xtest(int test) { cout << "Inside xtest!\n"; if(test) throw test; } int main() {cout <<"Start\n"; try { cout << "Inside try block\n"; xtest(0); xtest(1); xtest(2); } catch (int i) { cout << "Caught an exception, value is: "; cout << i <<"\n"; } cout << "End\n"; return 0; } // 捕获异常类 #include #include using namespace std; class MyException{ public: char how[80]; int what; MyException(){*how=0; what=0;} MyException(char *s, int n) {strcpy(how,s); what=n; } }; int main() {int i; try { cout <<"Enter a positive number: "; cin >> i; if(i<0) throw MyException("Not Positive",i); } catch (MyException e) { cout << e.how<<": "; cout << e.what <<"\n"; } return 0; } // 捕获派生异常类 #include using namespace std; class B { }; class D: public B { }; int main() {D derived; try { throw derived; } catch (D d) { cout << "Caught a derived class, not the base! \n"; } catch (B b) { cout << "Caught the base class! \n"; } return 0; } // 异常的限制及捕获所有异常 #include using namespace std; void xtest(int test) throw (int,char,double,char *) { try { if(test==0) throw test; if(test==1) throw 'a'; if(test==2) throw 12.34; if(test==3) throw "A string."; } catch (int i) { cout << "Caught an integer!"; } catch (...) { cout << "Caught Another!"; } } int main() {cout <<"Start\n"; xtest(0); xtest(1); xtest(2); xtest(3); cout << "End\n"; return 0; } // 异常的再次抛出 #include using namespace std; void xhandler() { try { throw "Hello!"; } catch (const char *) { cout << "Caught a string inside!\n"; throw; //rethrow char * out of function } } int main() {cout <<"Start\n"; try { xhandler(); } catch (const char *) { cout << "Caught a string outside!\n"; } cout << "End\n"; return 0; } // 一个简单的程序 #include using namespace std; int main() {int a,b; cout <<"Enter a b: "; cin >> a >> b; try { if(!b) throw b; cout << "Result: "<< a/b << endl; } catch (int i) { cout << "Can't divide by zero!\n"; } return 0; } ========================================= XV. 模板 //模板之通用函数 #include using namespace std; template void superSwap(X &a, X &b) { X t; t=a; a=b; b=t; }; int main() { int m=10, n=20; double x=10.1, y=20.2; char a='A', b='\x42'; superSwap(m,n); superSwap(x,y); superSwap(a,b); cout<<"m="<char* , int myfunc(1234.56, 20L); // double , long int return 0; } // 模板之通用类 #include using namespace std; const int Size=20; template class SuperStack{ DataType data[Size]; int top; public: SuperStack(){top= -1;} int push(DataType x); int pop(DataType &x); }; template int SuperStack::push(DataType x) { if(top>=Size-1) return -1; // stack is full data[++top]=x; return 0; } template int SuperStack::pop(DataType &x) { if(top<0) return -1; // stack is empty x=data[top--]; return 0; } int main() { SuperStack<char> chStack; SuperStack dbStack; char s[Size]="ABC"; double a[Size]={20.1, 21.2, 22.3}; int i; for(i=0;i<3;i++) { chStack.push(s[i]); dbStack.push(a[i]); } for(i=0;i<3;i++) { chStack.pop(s[i]); dbStack.pop(a[i]); } cout << s << '\n'; for(i=0;i<3;i++) cout << a[i]<<' '; cout<<'\n'; return 0; } ========================================= XVI. 名字空间 #include using namespace std; namespace GreenNamespace{ char Say[80]="TRUTH, Must thou Know!"; bool isUpperLetter(char ch) { if(ch>='A' &&ch<='Z')return true; return false; } class X{ public: int year; X(int y){year=y;} }; // note this semi-colon! } using namespace GreenNamespace; int main() {cout << Say <<'\n'; char *p=Say; int count=0; for(;*p;p++) if(isUpperLetter(*p))count++; cout << "count = " << count <<'\n'; X ob(2006); cout << ob.year <<"\n"; return 0; } //------------------------ ////////// OneCount.cpp//////// namespace BitsSpace{ int onePerByte(char x); int oneCount(char *buf,int bytes); // ------------------- int onePerByte(char x) {int count=0,i; for(i=0;i<8;i++) {if(x & '\x1') count++; // 'A'<=> '\x41' x>>=1; //x=x>>1; } return count; } // --- int oneCount(char *buf,int bytes) {int count=0,i; for(i=0;i #include "OneCount.cpp" using namespace std; //using namespace BitsSpace; const int SLen=80; // ---- int main(){ char ms[SLen],*p; cout<<"Enter your words:\n> " ; cin.getline(ms,SLen); cout<< BitsSpace::oneCount(ms,strlen(ms))<<"\n"; cout<<"Size of char: "<char)<<"\n"; return 0; } ========================================= //////////////////////////////// // XVII. C++ file handle, 6 programs // by Hs.li 2007.4.28 //////////////////////////////// // Write text strings! #include #include using namespace std; #define MaxN 200 // - - - - - - int main() {fstream outF; char text[MaxN]; cout<<"Enter lines, end with empty line:\n"; outF.open("str.txt",ios::out); if(!outF.is_open()) {cout<<"File open failed!\n"; return -1; } while(1) { cin.getline(text,MaxN); if(!text[0])break; outF<error!\n"; outF.close(); return -2; } } cout<<"Write text file okey!\n"; outF.close(); return 0; } ========================= // Read text strings! #include #include using namespace std; #define MaxN 200 // - - - - - - int main() {fstream inF; char text[MaxN]; cout<<"The text lines are:\n"; inF.open("str.txt",ios::in); if(!inF.is_open()) {cout<<"File open failed!\n"; return -1; } while(1) { inF.getline(text,MaxN); if(inF.eof()|inF.fail()|inF.bad())break; cout<error!\n"; inF.close(); return -2; } cout<<"---- End!\n"; inF.close(); return 0; } ====================== // Write text data! #include #include using namespace std; // - - - - - - int main() { const int MaxN=8; fstream outF; double a[MaxN]; char *fname="data.txt"; int i; cout<<"Please input 8 double: "; for(i=0;i<MaxN;i++) cin>>a[i]; outF.open(fname,ios::out); if(!outF.is_open()) {cout<<"File open failed!\n"; return -1; } outF.exceptions(fstream::failbit| fstream::badbit); try{ for(i=0;i<MaxN;i++) outF< #include using namespace std; // - - - - - - int main() { fstream inF; double b; char *fname="data.txt"; cout<<"Please wait for reading data:\n"; inF.open(fname,ios::in); if(!inF.is_open()) {cout<<"File open failed!\n"; return -1; } inF.exceptions(fstream::failbit| fstream::badbit|fstream::eofbit); try{ while(1) { inF>>b; cout< #include using namespace std; // - - - - - - int main() { const int MaxN=8; fstream outF; double a[MaxN]; char *fname="data.dat"; int i; cout<<"Please input 8 double: "; for(i=0;i<MaxN;i++) cin>>a[i]; outF.open(fname,ios::out|ios::binary); if(!outF.is_open()) {cout<<"File open failed!\n"; return -1; } outF.exceptions(fstream::failbit| fstream::badbit); try{ outF.write((char *)a,MaxN*sizeof(double)); } catch(std::exception &e) {cout<<"Exception caught:"< #include using namespace std; // - - - - - - int main() { fstream inF; double b; char *fname="data.dat"; cout<<"Please wait for reading data:\n"; inF.open(fname,ios::in|ios::binary); if(!inF.is_open()) {cout<<"File open failed!\n"; return -1; } inF.exceptions(fstream::failbit| fstream::badbit|fstream::eofbit); try{ while(1) { inF.read((char *)&b,sizeof(double)); cout<

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