Generic programming: function templates and class templates
Function template:
*template <typename T> //typename也可使用class
void func(T &a){
}*
There are two ways to use templates:
1. Automatic type deduction
func(a)
2、显式指定类型
func<int>(a)
The purpose of the template is to improve the reusability of the code and parameterize the type.
Notes:
·Automatic type derivation, must derive a consistent data type T before it can be used
·The template must determine the data type of T before it can be used
The difference between ordinary functions and templates:
automatic type inference will not have implicit type conversion, and
explicit type will have implicit type conversion
Calling rules for ordinary functions and template functions
· If both function templates and ordinary functions can be implemented, ordinary functions
will be called first
. Function templates can be forced through empty template parameter lists . Function templates can also be overloaded
. If function templates can generate more Good match, call function template first
Limitations of
templates : templates are not omnipotent, some specific data types need to be implemented in specific ways
·利用具体化的模板，可以解决自定义类型的通用化
E.g:
//不同类型排序模板
#include <iostream>
using namespace std;
template<typename T>
void mySwap(T &a, T&b)
{
T temp = a;
a = b;
b = temp;
}
template<class T>
void mySort(T arr[], int len)
{
for (int i = 0; i < len; i++){
int max = i;
for (int j = i + 1; j < len; j ++){
if (arr[max] < arr[j]){
max = j;
}
}
if (max != i){
mySwap(arr[max], arr[i]);
}
}
}
template<class T>
void printArray(T arr[], int len)
{
for (int i = 0; i < len; i ++)
{
cout << arr[i] << " ";
}
cout <<endl;
}
void test1()
{
char charArr[] = "fhdjkhfacb";
int num = sizeof(charArr);
mySort(charArr, num);
printArray(charArr, num);
}
void test2()
{
int intArr[] = {
4,455,345,22,4,55,6564,35,3,6757};
int num = sizeof(intArr) / sizeof(int);
mySort(intArr, num);
printArray(intArr, num);
}
int main()
{
test1();
test2();
system ("pause");
return 0;
}
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