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Homework 3 Solution

It is time  to learn  about  the power of polymorphism with  class inheritance.  To that end,  you  are  being  tasked  with  implementing  a  multi-robot  system.   Obviously,   a system this complex must be completed in multiple parts or milestones.

 

The  first milestone is a  baseline  robot class  along  with one  extension to a  tracked robot.   The  baseline  robot represents one  of many  and  so must have  a  guaranteed unique  name.   We are using tracked  robots  because  they  are easier to “steer”  than a robot which moves more like a car—using  Ackermann  steering.

 

This assignment is worth a total of 10 points:

 

• Up to 6 points for successful compilation and correctness,

 

• Up to 3 points for correctly following the Google style guide, and

 

• Up to 1 point for correct documentation.

 

 

Directory

 

You will notice that I have provided  you with the following directory structure:

 

• bin:  To contain executable binary  files.

 

• build:  To hold the intermediary .o object files.

 

• include:  All .h header  files will be located here.

 

• lib: A directory of useful classes for your project, provided  by me.  Normally this directory would hold true library  archives  which would get compiled into linkable  libraries.   This  is outside of the scope of this class.  I have provided  you a makefile for this directory and you may make all the .o files you need by running  “make  library”  from either the root directory 03hw/, or the lib directory 03hw/lib/.

 

• src: All .cc source files will be located here.

 

• test:  Directory  to hold the unit test source files which you will, hopefully,  write to test your classes before they are submitted.

 

MobileRobot:

 

Instances  of the MobileRobot  class represent  something  that can move,  without  describing  how it  moves. At this point, the only representation we care about is that it has a max speed stored as a double precision floating point value, and a unique  id stored as a C++ string object.

 

• Constructor(s): All mobile robots must know their max speed; therefore, MobileRobot shall have a default constructor which assumes speed is 0.0 units/time and a constructor which accepts speed as a double precision floating point value.  The constructor must assert that speed is non-negative.

 

• Destructor:  After a robot falls out of scope, its id shall no longer by non-unique.

 

• Accessor: Because different mobile robots may have different max speeds, create an accessor named speed which returns the mobile robot instance’s speed as a floating point value.  This method should promise the compiler it does not change any members’ value.

CSCE  240                                                                Homework 3                                                               Page 2 of 2

 

 

• Accessor: Mobile robots need some means by which to communicate if they are to coordinate or take direction from a controller.  This means they must each have a unique  name.  Create a method called id which  returns  an  instance’s  unique  name  as a string  from the C++ string  library.   The  method should return the name as an r-val and promise the compiler it will not change members’ values.

 

• Mutator:  A user may wish to assign a name  to a robot.  The  method id shall accept a string from the C++ string library  and return true if the string represents a unique  name,  false otherwise.  If the name is unique, the mutator shall assign the string to the robot instance’s id member variable.  Do not forget to set the robot’s previous  name as non-unique.

 

• IsUnique:  A good user might want to check whether a name is unique  for attempting to assign it to a robot instance. Provide  users of your class with a static method named  IsUnique which accepts a string from the C++ string library  and returns true if the string has not yet been assigned to a robot.

 

Tracked:

 

With the Tracked  class,  we extend the functionality of the MobileRobot class  by  providing  a  means  of translation between locations.  We may now represent our location as a point in two-space.  We shall also be able to query the robot about whether it can move from its current location to a desired location in a single step.

 

• Constructor(s):  Tracked  robots  need to know their  location  and  shall make  no assumptions  about such.  There  is no default constructor for a Tracked  Robot.  There  are two ways to provide location to a Tracked  instance,

 

1.  one uses a Point class instance from the lib/include/point.h library  and

2.  the other uses a pair of double precision floating points.

 

In either form, an additional double  may be provided  to set some initial speed.  If no initial speed is provided,  it is 0.0.

 

• Destructor:  After a robot falls out of scope, its id shall no longer by non-unique.

 

• Accessor: Tracked  robots shall be instantiated where they start and shall only move under  their own power,  this  means  there  shall be an accessor with  id location  which returns  a Point class instance from the csce240::two  dim namespace,  but not mutator to set the location.

 

• CanTranslateTo:  Before a robot is assigned  a location to which  it should  translate, it should  be established whether the robot can do so in a single step. The Tracked  class shall have a method named CanTranslateTo which accepts a Point class instance from the csce240::two dim namespace  and returns true when that point is no further than speed distance from its location.  You might look at the Vector class in the csce240::two  dim namespace  from lib/include/vector.h lib

 

Submission: To  get credit, you  must upload  a zipped  (not tarred, gzipped,  or 7z) archive containing your submission  files in the the directory tree provided.  Given the difficulty I have seen with so many student unable  to successfully create and archive files, you will archive ONLY the directory structure which I provided  you.

Late submissions  will be handled  as per syllabus.  I am attempting to fit four more assignments into this semester so that struggling students have  a chance  to bring  up their grade;  consequently, there will be no extensions.

 

 

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