Implement the interface from mystring.h using dyamically$-$allocated

strings that will allocate exactly the correct amount of memory to store their

characters. But they will also have an arbitrary maximum length of

MAX$\_$STRING$\_$LENGTH, which will be defined elsewhere.

Assume the code you write will be saved to mystring.c; write the complete

contents of that file. Implement only the data structure; do not write a main

program. Write appropriate contracts.