In this problem, you will write a class to implement a very simple word processor $($only

one line of text is allowed$).$

$($a$)$ Write the class LineEditor which stores a line of text $($a list of characters$)$ as

well as a cursor position $($an iterator into the list$).$ The cursor is allowed to point

to any character in the line of text, as well as one character after the line. Use

the file names LineEditor.h and LineEditor.cc$.$

Your class should provide the following member functions:

$$ Default constructor: initializes an empty line of text. The cursor should be

placed one character past the end of the line.

$$ void left$()$: moves the cursor to the left by one character. If the cursor is

already at the beginning, this function does nothing.

$$ void right$()$: moves the cursor to the right by one character. If the cursor

is already pointing to one character past the end, this function does nothing.

$$ void insert$($const string& s$)$: inserts the string s into the current position.

The cursor should be positioned after the inserted string. Note: the

iterator remains unchanged and valid after list::insert$(),$ so it does

not need updating.

$1$

$$ void erase$()$: erases the character at the current position. The cursor

should be positioned at the character immediately after the one erased. If

the cursor is past the end of the line, this function does nothing.

$$ void change$($char c$)$: changes the character at the current position to c$.$

The cursor should be positioned at the changed character. If the cursor points

to one past the end of the line, then this function should behave exactly the

same way as insert.

$$ void apply$($char $(*$f$)($char c$))$: applies the function f to every character

c in the line, and replaces the character by f$($c$).$

Also provide a friend function to print the line:

ostream& operator$<<($ostream& os$,$ const LineEditor& le$)$;

The line of text is first printed, ended with the symbol $ to mark the end of line.

The next line contains a single character $^$ to indicate the position of the cursor.