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Homework 4 Solution

It is time to learn more about the power of polymorphism with class inheritance using abstract classes with pure virtual functions.

 

We need to update the MobileRobot class, update the Tracked class, and  implement the QuadRotor class.

 

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

 

We will continue using 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 04hw/, or the lib directory 04hw/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. We need to update and implement the following:

 

• 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.  These may be the same constructor. In addition to assigning a non-negative speed, the constructor shall also provide  the new instance a unique  name.

 

• Destructor:  After a robot falls out of scope,  its id   shall  no longer  be non-unique.    This  method should be virtual so that if a MobileRobot pointer is deleted, the child’s destructor will be called.

 

• 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.

 

 

 

• 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.

 

• Accessor: Given the new class hierarchy  of the Point class, we can now maintain the location   in the MobileRobot class and  should move the accessor here.  The method’s id should be location and return value should be an r-val pointer to a Coordinate and should promise not to change the calling object.

 

• CanTranslateTo:  With the new class hierarchy  of the Point class, the CanTranslateTo method can be made  pure  virtual and  moved  to the class.  Its parameter should  be changed  to an  unmodifiable Coordinate pointer.

 

• Translate:  This method accepts an unmodifiable  Offset pointer and attempts to move the robot in that direction and for that distance, to the limit of its speed.

 

• 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:

 

The  Tracked class now implements a virtual parent and  so we must be mindful  to implement all virtual functions if was want to instantiate objects of the class.  In addition, we must modify the class to make use of the new Point and Vector class hierarchies.  Note that Tracked will only use two-dimensional geometry.

 

• 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 Coordinate pointer 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.  Be mindful  of the way in which location   is managed.   You should  create  and destroy memory to copy the value(s)  given in the destructor.

 

• Destructor:  In addition  to the work done  in a parent constructor,  the memory  for the location

must be managed.

 

• CanTranslateTo:  Implement this method as described  in the parent class.

 

• Translate:  Implement this method as described  in the parent class.

 

QuadRotor:

 

The  QuadRotor class  implements a  virtual parent and  so we must be  mindful  to implement all  virtual functions if we want to instantiate objects of the class.

 

 

 

• 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 Coordinate pointer from the lib/include/point.h library  and

2.  the other uses a trio 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.  Be mindful  of the way in which location   is managed.   You should  create  and destroy memory to copy the value(s)  given in the destructor.

 

• Destructor:  In addition  to the work done  in a parent constructor,  the memory  for the location

must be managed.

 

• CanTranslateTo:  Implement this method as described  in the parent class.

 

• Translate:  Implement this method as described  in the parent class.

 

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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