Computation and Logic: Assessed Assignment 1 Informatics 1 01.10.2004
Informatics 1 Computation and Logic
Assessed Assignment 1
Out on Friday 1st October 2004, due noon Friday 15th October 2004
Your answers to all the questions in this assignment should be stored in
a single file called CLExOne.txt which has your name and matriculation
number on the first line. If you use different files when working on this
assessment then integrate them into CLExOne.txt before submission.
Submit CLExOne.txt before the deadline using the following command:
Shell> submit inf1 inf1a cl1 CLExOne.txt
You may discuss this assignment with other students but your submission
should be based on your own work. If you do include work carried out in
collaboration with others you must properly attribute any contributions
that they made to the work. Keep in mind that you are responsible for
deriving educational value from your assignments.
In this exercise you will use a simple proof system. It is written in the Prolog
programming language which you do not learn in this course, although we will
mention it in a few weeks time. Prolog programs are run by providing goals
for the system to solve, so when you are asked to “give a goal” to Prolog that
means to type in an expression for Prolog to attempt to solve. Prolog then comes
back with a yes (plus perhaps some values for variables) if it finds a solution or
answers no if it cannot find a solution. You then press carriage return before
giving further goals.
First copy the code for the proof system to the file prover.pl in your own
directory by going to the Informatics 1 Computation and Logic Web page and
downloading the file from the link on that page labeled “Prover for Assessed
Exercise 1” (ask a demonstrator if you don’t know how to download a file from a
Web page). You do not need to look at the contents of this file.
To start the proof system do the following:
•Give the command sicstus to start the Prolog system.
•Then type [prover]. to load the file into Prolog. Remember to type the full
stop at the end (a full stop is the symbol that tells Prolog you have finished
a definition or instruction).
Now try your first proof with this system. This will be the proof that the
proposition bfollows from the assumptions [a, a →b]. Give the following goal (by
typing it in as given below). Rember the full stop and carriage return.
prove([a, a ---> b], b).
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