CS 1001 Assignment 6
Assigned: Tuesday, April 25, 2000 Due: Wednesday, May 3, 2000

Problem

Write a set of subroutines to do the following:
a.     delete a substring from a source string
b.     insert a new string in a source string at a specified position
c.     indicate where a specified target string occurs in the source string
d.     replace the first occurrence of a specified substring in a source string with another

Test these procedures by writing a text editor and performing several editing operations. The editor should be driven by the following menu:

Enter the first letter of an edit operation described as follows:

D - Delete a substring
E - Enter a source string to be edited
I - Insert a substring
L - Locate a substring
P - Print the source string
R - Replace one substring with another
S - Show the menu
Q - Quit

A sample run of the program is given here to clarify how the program should behave:

%a.out
Text Editor Program

You will be able to edit text by choosing from the
following list of commands:

Enter

      D to delete a substring from the source string
      E to enter a source string to be edited
      I to insert a substring in the source string
           at a specified position
      L to locate the position of a substring in the
           source string
      P to print the source string
      R to replace one substring with another
      S to show this menu
      Q to quit

What is your choice?
e
Enter string

This*is*a*string.

What is your choice?
d
Enter string to be deleted
is

What is your choice?
p
Th*is*a*string.

What is your choice?
l
Enter string to locate
*is

What is your choice?
i
Enter string to be inserted
at

What is your choice?
p
That*is*a*string.

What is your choice?
r
Enter old string
is

Enter new string
is*not

What is your choice?
p
That*is*not*a*string.

What is your choice?
d
Enter string to be deleted
thing
string not found

What is your choice?
p
That*is*not*a*string.

What is your choice?
i
Enter string to be inserted
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Can't insert; string would exceed 80 characters

What is your choice?
i
Enter string to be inserted
+++

What is your choice?
p
Th+++at*is*a*string.

What is your choice?
q

Assumptions and Restrictions

You should assume that the maximum size of a string is 80 characters. The string that is being edited should, therefore, be declared in the main program as

      CHARACTER (80) ::  string

and all changes to the string will be implemented using the string subprograms defined in Chapter 11.

Hints

We will go over the string functions Thursday 4/7. There is an example of a text editor on pages 781-785 of the text
Each of the menu items should be implemented in a separate subroutine. Rather than try to write the entire program at once, approach it incrementally: implement the Enter and Print subroutines first, then add the others one at a time, thoroughly testing each one before you attempt the next. When using an incremental approach like this, the subroutines that aren't functional yet are usually written as ``stubs'' (pp. 459).

Grading

This assignment will be graded based on 100 points. Point values will be allocated as follows:

Documentation: (20 points) Introductory comment, meaningful identifiers, proper use of indentation and blank lines, comments for variables, algorithm comments. Each subprogram must be adequately commented, including pre- and post-conditions!
Functionality: (50 points) The program must work correctly on our test data.
Modularity and Design: (10 points) The main program should be simple and easy to follow. Each menu item should be implemented as a separate subprogram. Parameters must be used to pass information to the subprograms.
Error handling and Testing: (20 points) See the sample execution for ideas; each subprogram should check for and report error conditions. The script file should show thorough testing of the program.

Deliverables

Using turnin, turn in your Fortran source file and a script file showing successful compilation and program execution. Your files must be turned in prior to 12:00 pm on Wednesday, May 3. The command you should use to turn in your files is

/cs/bin/turnin submit cs1001 hw6 hw6.f90 hw6.script