C++: C-Strings - Programming Exercises 1

Programming problems

1. Write a myStrlen function which is the same as the library strlen function. Assume the prototype is

       int myStrlen(char a[]);
       int myStrlen(char* a);

2. Write the myStrcpy function which is the same as the library strlen function. Assume the prototype is

       void myStrcpy(char a[], char b[]);
       void myStrcpy(char* a, char* b);

3. Write the myStrcat function which is the same as the library strlen function. Assume the prototype is

       void myStrcat(char a[], char b[]);
       void myStrcat(char* a, char* b);

4. Write the myStrcmp function which is the same as the library strlen function. Assume the prototype is

       int myStrcmp(char a[], char b[]);  // array version
       int myStrcmp(char* a, char* b);    // pointer version

   For example,

            i = myStrcmp("abc", "after");  // result is a negative value

   There is a slight twist to this problem. The standard allows each compiler to decide if the char type is signed or not, so the range of of a char is either -128..127 (signed) or 0..255 (unsigned). To do the comparison properly, the comparison should be done on the unsigned characters, which requires casting to that type.

Guidelines for problems

• No I/O (cin or cout) should be in these functions (other than temporary I/O for debugging purposes). As a general design principle, I/O should be restricted to a few functions which are specifically used for this purpose. There is no need for I/O in these functions.
• No function need to allocate space for temporary arrays. The arrays which are passed as parameters are sufficient.
• These functions can be written in either array-style or pointer-style.