ECS40  Homework 1 

ECS40 
Homework 1 
Use the handin directory hw1 to submit your work
Fraction calculator
Description
Create a simple fraction calculator that can add and subtract any number of fractions and writes
the answer as a reduced fraction.
Your program will read input from stdin and write output on stdout.
A fraction is represented as the sequence:
a/b
where a and b are integers and any amount of white space characters ' ' (including none) can
separate a from '/' and '/' from b.
Input consists of an expression made of fractions separated by the operators '+' or '-'.
The number of fractions in the expression is arbitrary. Each of the following 6 lines is an
example of valid input expression:
1/2 + 3/4
1/2-5/7+3/5
355/113
3 /9- 21 / -7
4/7-5/-8
-2/-3 +7 /5
Note that the numerator and/or denominator of a fraction given as input may be negative.
The input will consist of a single expression on a single line terminated by a \n character.
The output should consist of a single, irreducible fraction written as
c/d
where c is a signed integer and d is a positive integer (i.e. the denominator cannot be negative in
the output). The numbers c and d should not have any common factors (apart from 1).
Error processing and special cases
You can expect the input to consist of complete expressions, i.e. there will be no incomplete or
missing fractions in the input. Fractions with a zero denominator may appear in input, and must
cause the following error message to be printed on stdout:
Error: denominator is zero
with no other output.
If the answer is an integer, the program should only print that integer and not a fraction
Example: input= 3/2 + 4/8 , output = 2
Examples of input and corresponding output will be provided on the web site site
web.cs.ucdavis.edu/~fgygi/ecs40 . Your output should exactly match the output in the example
files.
Implementation
The main program, called calculator.cpp , is provided. Your project must include a class
Fraction that encapsulates all functions related to the processing of fractions. The and <<
operators must be overloaded and used to read and write fractions. The presence of a zero
denominator in input should be handled by throwing an exception of type
invalid_argument defined in <stdexcept. The class Fraction must be defined in a
source file Fraction.cpp and declared in a header file Fraction.h. The implementation
of the member functions should be defined in the file Fraction.cpp. The class Fraction must
include a constructor Fraction::Fraction(int a, int b). The internal
representation of the fraction should be in reduced form, i.e. using a pair of numbers that have no
common factors. Constructors and other member functions must ensure that the fraction is
always reduced. Use Euclid's algorithm to simplify fractions to reduced form. An example of a C
implementation of this algorithm is provided on the web site web.cs.ucdavis.edu/~fgygi/ecs40 in
the example programs of Lecture 1. The operators '+', '-' and '=' must be overloaded and
defined. Member functions getNum() and getDen() should be implemented, returning the
(reduced) numerator and denominator of the fraction. It should be possible to use the class
Fraction in the program useFraction.cpp which #includes the header
Fraction.h. The program useFraction.cpp is provided on the web site
web.cs.ucdavis.edu/~fgygi/ecs40. You should not modify that program.
Submission
Create a tar file named hw1.tar containing the files calculator.cpp Fraction.cpp
Fraction.h useFraction.cpp and Makefile. Do not compress the tar file. The files
calculator.cpp and useFraction.cpp must be identical to the files provided. The
Makefile must contain a target calculator , a target useFraction and a target all. The
target all should appear first and will be used to build both executables. The Makefile should
include the necessary definition to compile C++ files with the –Wall option. Include your name
and Student ID in a comment at the top of each file (except calculator.cpp and
useFraction.cpp). Submit your project using:
$ handin cs40 hw1 hw1.tar