CS 3721: Programming Languages Lab

Lab #01 Solutions: Basic Scheme: learn a new language.

First, start the DrScheme programming environment. You can download various versions of

DrScheme

from http://www.drscheme.org or use the environment installed on the depart-

ment Linux machines (by running \

drscheme

"). The web site, http://www.drscheme.org,

has comprehensive documentation both about

DrScheme

and about the

Scheme

language

itself. Various reference material for Scheme and Dr. Scheme can be found at

http://download.plt-scheme.org/doc/; the Revised

5

Report on the Algorithmic Language

Scheme is the ocial denition of Scheme.

After the

DrScheme

environment starts, it will open a window with two panels: the top

panel (called the

denition window

) is for entering programs and saving commands to les;

the bottom

interactive window

is for experimenting with Scheme commands without saving

them. (Your commands in the interactive window can use denitions in the denition

window.) You should periodically save your code in the

denition window

into a le so that

your work is not lost.

Dr. Scheme implements several variations of the Scheme language. For the purpose of our

class, you should use the language level, \Teaching Languages: Intermediate Student with

lambda." (You can choose the language level when you rst start \drscheme" or by clicking

menu item \language:choose language").

Goals of this lab:



Interact with, write and debug programs in Dr. Scheme; Understand, read, and write

simple expressions in Lisp/Scheme's prex notation; Use the operator,

dene

, to give

symbolic names to expressions; Write numeric expressions using basic operators (e.g.,

+, -, /, sqrt, and =); Understand Lisp/Scheme lists and be able to use the

cons, car,

cdr, null?

, and

pair?

operators.

You can work on the questions in small groups of 1-3 individuals each. However, you have to

write up your solution on your own

. Also, you should list the names of each individual

in your group.

Due date: January 29, 3:30pm.

At the beginning of the next recitation.

In this lab, we start with the most primitive concepts in Scheme.

1. First is the atom, syntactically, an

atom

can be any string of characters that does not

contain any parentheses or spaces, and it will be treated as a single atomic unit when

building up data structures. An atom can be a variable name, a number, or a symbol.

At the interactive window, try entering some atoms (i.e., symbols and numbers).

You may need to use

0

:::

or

(

quote :::

)

for symbols, for example,

0

programming

or

(

quote programming

)

.

Please list 5 atoms.

Solution:

for numbers:

>

5

1