Summary: In this laboratory, you will experiment with the use and application of some of Scheme's basic input and output procedures.
a. Make sure that you understand what
are supposed to do. You may find
the reading on the topic helpful.
b. Start DrScheme.
For each of the parts of this exercise, you should use something like
(define val (read))
to read in a value.
read to obtain a number.
read to obtain a string.
read to obtain a character.
read to obtain a list of numbers.
read to obtain a symbol.
read to obtain a list that contains a number,
string, and symbol.
g. What happens when you use
read to obtain a list and
you hit <Enter> in the middle of the list?
Consider the following sequence of Scheme commands:
(display "Please enter a value and I will square it: ") (define val (read)) (define val-squared (* val val)) (display (string-append "The value of " (number->string val) " squared is " (number->string val-squared))) (newline)
a. What do you expect the code to do?
b. Verify your answer via experimentation.
a. Save the above code in a file (e.g.,
b. Open a terminal window.
c. In that terminal window, type
mzscheme -r file.scm
Where file.scm is the name you chose in part a.
d. Reflect on what happened. Did you need to type any Scheme? Could someone else use step c without understanding the underlying Scheme?
Rewrite the code from the previous exercise to use
let* (or both) rather than
a. What happens if someone enters something other than a number?
b. Update your program so that it prints a friendly error message
display) and then asks again if someone enters
something other than a number.
a. Write a Scheme program that reads in the three coefficients of a quadratic equation (the a, b, and c in ax2 + bx + c) and prints out the roots of the equation. You should model this program on the previous exercsies.
b. Save the program in a file and execute it from the command line.
c. Reflect on what happened. Did you need to type any Scheme? Could someone else use step c without understanding the underlying Scheme?
Write a program repeatedly asks for a value and computes its square root. You will probably need to
a. Put the stuff (request for value, computation of a value, display of that value) in a procedure.
b. Have that procedure recurse.
c. Decide upon a base case to stop recursion. (I'd suggest that you stop when someone enters something other than a number.)
Friday, 2 March 2001 [Samuel A. Rebelsky]
Monday, 4 November 2002 [Samuel A. Rebelsky]
Tuesday, 5 November 2002 [Samuel A. Rebelsky]
I usually create these pages
on the fly, which means that I rarely
proofread them and they may contain bad grammar and incorrect details.
It also means that I tend to update them regularly (see the history for
more details). Feel free to contact me with any suggestions for changes.
This document was generated by
Siteweaver on Mon Dec 2 09:18:56 2002.
The source to the document was last modified on Tue Nov 5 09:29:45 2002.
This document may be found at