strlen的实现

#include <iostream>
#include <assert.h>
#include <string>

int str_len(const char* str){ //这里声明const保证不会被修改
    assert(str!=NULL); 
    /*用户可能随意传参，断言阻止编译器抛出错误；如果出错，直接退出*/
    int length = 0;
    while (*str++!='\0') {
           length++;
    }
    return length;
}
int main(int argc, const char * argv[]) {
    // insert code here...
    //test
    char greeting[] ="hello";
    std::cout<<str_len(greeting)<<std::endl;//5
    std::cout << "Hello, World!\n";
    return 0;
}