c++高手请进：设计字符串类，该类的对象实现如下运算。

class myString {
private:
int len;
char* data;

public:
myString() {
len = 0;
data = 0;
}
~myString() {
delete[] data;
}

myString& operator=(const char* str) {
len = strlen(str);
char* newData = new char[len + 1];
strcpy(newData, str);
delete[] data;
data = newData;
return *this;
}
myString& operator=(const myString& str) {
len = strlen(str.data);
char* newData = new char[len + 1];
strcpy(newData, str.data);
delete[] data;
data = newData;
return *this;
}

const myString operator+(const char* str) const {
myString ret;
ret.len = len + strlen(str);
ret.data = new char[len + 1];
strcpy(ret.data, data);
strcp