Homework 1 SOlution


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Use the handin directory hw1 to submit your work

Fraction calculator


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:


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



3 /9- 21 / -7


-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


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.


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.


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

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