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CS 368 (Summer 2009) — Day 2 Homework

Due Thursday, July 16th, at the start of class.


Write a Perl script that guesses a number that the user has in mind.


This should be a fairly straightforward exercise that uses basic Perl syntax: loops, conditionals, variables, etc.

The user will run the script, think of a number between 1 and 100, and then the script will repeatedly guess what the number is. For each guess, the user indicates whether it is correct, too high, or too low. A typical interaction might look like this:

% homework-02-script
Welcome to the number-guessing game!
Think of a number between 1 and 100.

I guess 50.
Is this (c)orrect, (h)igh, or (l)ow? h
Too high, I'll guess lower.

I guess 25.
Is this (c)orrect, (h)igh, or (l)ow? l
Too low, I'll guess higher.

I guess 42.
Is this (c)orrect, (h)igh, or (l)ow? c
I got it!


While a binary search is clearly the optimimal strategy here, it does not really matter what strategy your script implements as long as it is guaranteed to find the answer eventually. Depending on the particular strategy you use, there are some simple Perl expressions that we have not discussed in class but that may be helpful. For example, you can get the integer portion of a floating-point number like this:

my $x = int(23 / 5);

And if you want a random floating point number in the range [0, n), you can do this:

my $x = rand($n);

The two expressions above can, of course, be combined to get a random integer between 0 and ($n-1):

my $x = int(rand($n));


Do the work yourself, consulting reasonable reference materials as needed; any reference material that gives you a complete or nearly complete solution to this problem or a similar one is not OK to use. Asking the instructors for help is OK, asking other students for help is not.

Hand In

A printout of your script on a single sheet of paper. At the top of the printout, please include “CS 368 Summer 2009”, your name, and “Homework 02, July 16, 2009”. Identifying your work is important, or you may not receive appropriate credit.