{"id":32,"date":"2024-08-01T18:35:48","date_gmt":"2024-08-01T18:35:48","guid":{"rendered":"https:\/\/bhiggs.x10hosting.com\/PracticalC%2B%2BProgramming\/?page_id=32"},"modified":"2025-01-20T20:27:57","modified_gmt":"2025-01-20T20:27:57","slug":"assignment-3","status":"publish","type":"page","link":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/assignments\/assignment-3\/","title":{"rendered":"Assignment 3"},"content":{"rendered":"\n

<\/span>“Smoke and Mirrors”<\/span><\/h2>\n\n\n\n

<\/span>Part 1: The Nothing<\/code><\/strong> Class<\/span><\/h3>\n\n\n\n

Here’s a ‘useful’ class:<\/p>\n\n\n\n

\n
\n
<\/path><\/path><\/svg><\/span>
\/\/<\/span><\/span>\n\/\/  Nothing.h<\/span><\/span>\n\/\/  Assignment 3: Smoke & Mirrors<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 10\/31\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#ifndef<\/span> Nothing_h<\/span><\/span>\n#define<\/span> Nothing_h<\/span><\/span>\n<\/span>\nclass<\/span> <\/span>Nothing<\/span><\/span>\n{<\/span><\/span>\n};<\/span><\/span>\n<\/span>\n#endif<\/span> \/* Nothing_h *\/<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
\n
… and here is a similarly useful program that uses it:<\/p>\n\n\n\n
<\/path><\/path><\/svg><\/span>
\/\/<\/span><\/span>\n\/\/  TestNothing.cpp<\/span><\/span>\n\/\/  Assignment 3: Smoke & Mirrors<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 10\/31\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span>"Nothing.h"<\/span><\/span>\n<\/span>\nint<\/span> <\/span>main<\/span>(<\/span>int<\/span> <\/span>argc<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span> <\/span>argv<\/span>[])<\/span><\/span>\n{<\/span><\/span>\n  <\/span>const<\/span> Nothing ness;<\/span>  \/\/ Some compilers don't like this<\/span><\/span>\n  \/<\/span>const<\/span> Nothing ness = <\/span>Nothing<\/span>();<\/span>  \/\/ so try this instead<\/span><\/span>\n<\/span>\n  Nothing <\/span>doing<\/span>(ness);<\/span>  \/\/ If your compiler doesn't like this<\/span><\/span>\n  \/\/Nothing doing = ness;  \/\/ try this instead<\/span><\/span>\n<\/span>\n  doing = ness;<\/span><\/span>\n<\/span>\n  Nothing *here = &doing;<\/span><\/span>\n  <\/span>const<\/span> Nothing *anywhere = &ness;<\/span><\/span>\n<\/span>\n  <\/span>return<\/span> <\/span>0<\/span>;<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n<\/div>\n\n\n\n
Convince yourself that this program compiles without error, and executes without failure.<\/p>\n\n\n\n
Explain why. What did the C++ compiler do for you?<\/p>\n\n\n\n
Write a Nothing<\/code><\/strong> class that does exactly the same thing as the (empty) one above, but where you supply all the equivalent member functions explicitly. Just change Nothing.h<\/code><\/strong>.<\/p>\n\n\n\n
Compile and link the TestNothing.cpp<\/code><\/strong> file against your version of the Nothing<\/strong> class, and show that your member functions get called at the right places.<\/p>\n\n\n\n
<\/span>Part 2: An Expedition into Efficiency<\/span><\/h3>\n\n\n\n
Consider the following simple MyString<\/code><\/strong> class:<\/p>\n\n\n\n
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<\/path><\/path><\/svg><\/span>
\/\/<\/span><\/span>\n\/\/  MyString.h<\/span><\/span>\n\/\/  Assignment 3: An Expedition into Efficiency<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 10\/31\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#ifndef<\/span> MyString_h<\/span><\/span>\n#define<\/span> MyString_h<\/span><\/span>\n<\/span>\n\/\/<\/span><\/span>\n\/\/ mystring.h (Not to be confused with string.h!)<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/ A minimal string class<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><string><\/span> <\/span>\/\/ for strlen(), strcpy()<\/span><\/span>\n#include<\/span> <\/span><iostream><\/span> <\/span>\/\/ for ostream stuff<\/span><\/span>\n<\/span>\nclass<\/span> <\/span>MyString<\/span><\/span>\n{<\/span><\/span>\npublic:<\/span><\/span>\n  <\/span>MyString<\/span>()<\/span><\/span>\n    : <\/span>m_len<\/span>(<\/span>0<\/span>), <\/span>m_ptr<\/span>(<\/span>new<\/span> <\/span>char<\/span>[<\/span>1<\/span>])<\/span><\/span>\n  { <\/span>m_ptr<\/span>[<\/span>0<\/span>] = <\/span>'<\/span>\\0<\/span>'<\/span>; }<\/span><\/span>\n<\/span>\n  <\/span>MyString<\/span>(<\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span>str<\/span>)<\/span><\/span>\n    : <\/span>m_len<\/span>(<\/span>strlen<\/span>(str))<\/span><\/span>\n  {<\/span><\/span>\n    m_ptr = <\/span>new<\/span> <\/span>char<\/span>[m_len+<\/span>1<\/span>];<\/span><\/span>\n    <\/span>strcpy<\/span>(m_ptr, str);<\/span><\/span>\n  }<\/span><\/span>\n<\/span>\n  <\/span>MyString<\/span>(<\/span>const<\/span> <\/span>MyString<\/span> <\/span>&<\/span>src<\/span>)<\/span><\/span>\n    : <\/span>m_len<\/span>(<\/span>src<\/span>.<\/span>m_len<\/span>), <\/span>m_ptr<\/span>(<\/span>new<\/span> <\/span>char<\/span>[<\/span>src<\/span>.<\/span>m_len<\/span>+<\/span>1<\/span>])<\/span><\/span>\n  { <\/span>strcpy<\/span>(m_ptr, <\/span>src<\/span>.<\/span>m_ptr<\/span>); }<\/span><\/span>\n<\/span>\n  <\/span>~MyString<\/span>()<\/span><\/span>\n  { <\/span>delete<\/span> <\/span>[]<\/span> m_ptr;<\/span> \/* Clean up *\/<\/span> }<\/span><\/span>\n<\/span>\n  <\/span>MyString<\/span> <\/span>&<\/span>operator=<\/span>(<\/span>const<\/span> <\/span>MyString<\/span> <\/span>&<\/span>src<\/span>)<\/span><\/span>\n  {<\/span><\/span>\n    <\/span>if<\/span> (<\/span>this<\/span> != &src)<\/span>  \/\/ Prevent assignment to self, causing corruption<\/span><\/span>\n    {<\/span><\/span>\n      <\/span>delete<\/span> <\/span>[]<\/span> m_ptr;<\/span> \/\/ Clean up previously allocated space first<\/span><\/span>\n      m_len = <\/span>src<\/span>.<\/span>m_len<\/span>;<\/span><\/span>\n      m_ptr = <\/span>new<\/span> <\/span>char<\/span>[m_len+<\/span>1<\/span>];<\/span><\/span>\n      <\/span>strcpy<\/span>(m_ptr, <\/span>src<\/span>.<\/span>m_ptr<\/span>);<\/span><\/span>\n    }<\/span><\/span>\n    <\/span>return<\/span> *<\/span>this<\/span>;<\/span><\/span>\n  }<\/span><\/span>\n<\/span>\n  <\/span>friend<\/span> <\/span>std<\/span>::<\/span>ostream<\/span> <\/span>&<\/span>operator<<<\/span>(<\/span>std<\/span>::<\/span>ostream<\/span> <\/span>&<\/span>o<\/span>,<\/span><\/span>\n                                  <\/span>const<\/span> <\/span>MyString<\/span> <\/span>&<\/span>src<\/span>)<\/span><\/span>\n  { <\/span>return<\/span> o << <\/span>src<\/span>.<\/span>m_ptr<\/span>; }<\/span><\/span>\n<\/span>\nprivate:<\/span><\/span>\n  <\/span>size_t<\/span>  m_len;<\/span>  \/\/ length of string, in chars<\/span><\/span>\n  <\/span>char<\/span>*   m_ptr;<\/span>  \/\/ pointer to allocated array of chars<\/span><\/span>\n  };<\/span><\/span>\n<\/span>\n#endif<\/span> \/* MyString_h *\/<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
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Now consider the simple Person<\/code><\/strong> class:<\/p>\n\n\n\n
<\/path><\/path><\/svg><\/span>
\/\/<\/span><\/span>\n\/\/  Person.h<\/span><\/span>\n\/\/  Assignment 3: An Expedition into Efficiency<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 10\/31\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#ifndef<\/span> Person_h<\/span><\/span>\n#define<\/span> Person_h<\/span><\/span>\n<\/span>\n\/\/<\/span><\/span>\n\/\/  A very simple Person class.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n#include<\/span> <\/span>"MyString.h"<\/span><\/span>\n<\/span>\nclass<\/span> <\/span>Person<\/span><\/span>\n{<\/span><\/span>\npublic:<\/span><\/span>\n  <\/span>Person<\/span>(<\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span>n<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span>adr<\/span>, <\/span>int<\/span> <\/span>ag<\/span>)<\/span><\/span>\n    : <\/span>m_name<\/span>(n), <\/span>m_address<\/span>(adr), <\/span>m_age<\/span>(ag)<\/span><\/span>\n  {}<\/span><\/span>\n<\/span>\n  <\/span>virtual<\/span> <\/span>~Person<\/span>() {}<\/span><\/span>\n<\/span>\n  <\/span>int<\/span> <\/span>IsOlder<\/span>(<\/span>const<\/span> <\/span>Person<\/span> <\/span>&<\/span>other<\/span>)<\/span><\/span>\n  { <\/span>return<\/span> m_age > <\/span>other<\/span>.<\/span>m_age<\/span>; }<\/span><\/span>\n<\/span>\n  <\/span>void<\/span> <\/span>Print<\/span>()<\/span><\/span>\n  {<\/span><\/span>\n    <\/span>std<\/span>::cout << <\/span>"Name: "<\/span>    << m_name    << <\/span>std<\/span>::endl<\/span><\/span>\n              << <\/span>"Address: "<\/span> << m_address << <\/span>std<\/span>::endl<\/span><\/span>\n              << <\/span>"Age: "<\/span>     << m_age     << <\/span>std<\/span>::endl;<\/span><\/span>\n  }<\/span><\/span>\n<\/span>\nprivate:<\/span><\/span>\n  MyString m_name;<\/span>     \/\/ Person's name<\/span><\/span>\n  MyString m_address;<\/span>  \/\/ Person's address<\/span><\/span>\n  <\/span>int<\/span>      m_age;<\/span>      \/\/ Person's age<\/span><\/span>\n};<\/span><\/span>\n<\/span>\n#endif<\/span> \/* Person_h *\/<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n
… and the simple Student<\/code><\/strong> class:<\/p>\n\n\n\n
<\/path><\/path><\/svg><\/span>
\/\/<\/span><\/span>\n\/\/  Student.h<\/span><\/span>\n\/\/  Assignment 3: An Expedition into Efficiency<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 10\/31\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#ifndef<\/span> Student_h<\/span><\/span>\n#define<\/span> Student_h<\/span><\/span>\n<\/span>\n\/\/<\/span><\/span>\n\/\/  A very simple Student class.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n#include<\/span> <\/span>"Person.h"<\/span><\/span>\n#include<\/span> <\/span>"MyString.h"<\/span><\/span>\n<\/span>\nclass<\/span> <\/span>Student<\/span> : <\/span>public<\/span> <\/span>Person<\/span><\/span>\n{<\/span><\/span>\npublic:<\/span><\/span>\n  <\/span>Student<\/span>(<\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span>nam<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span>adr<\/span>, <\/span>int<\/span> <\/span>ag<\/span>,<\/span><\/span>\n          <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span>sch<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span>schadr<\/span>)<\/span><\/span>\n    : <\/span>Person<\/span>(nam, adr, ag),<\/span><\/span>\n      <\/span>m_schoolName<\/span>(sch), <\/span>m_schoolAddress<\/span>(schadr)<\/span><\/span>\n  {}<\/span><\/span>\n<\/span>\n  <\/span>virtual<\/span> <\/span>~Student<\/span>() {}<\/span><\/span>\n<\/span>\n  <\/span>void<\/span> <\/span>Print<\/span>()<\/span><\/span>\n  {<\/span><\/span>\n    <\/span>Person<\/span>::<\/span>Print<\/span>();<\/span><\/span>\n    <\/span>std<\/span>::cout << <\/span>"Attending: "<\/span> << m_schoolName << <\/span>std<\/span>::endl<\/span><\/span>\n              << <\/span>" "<\/span> << m_schoolAddress << <\/span>std<\/span>::endl;<\/span><\/span>\n  }<\/span><\/span>\n<\/span>\nprivate:<\/span><\/span>\n  MyString m_schoolName;<\/span><\/span>\n  MyString m_schoolAddress;<\/span><\/span>\n};<\/span><\/span>\n<\/span>\n#endif<\/span> \/* Student_h *\/<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n<\/div>\n\n\n\n
Finally, consider the following main program:<\/p>\n\n\n\n
\n
\n
<\/path><\/path><\/svg><\/span>
\/\/<\/span><\/span>\n\/\/  TestStudent.cpp<\/span><\/span>\n\/\/  Assignment 3: An Expedition into Efficiency<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 10\/31\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n#include<\/span> <\/span>"Student.h"<\/span><\/span>\n<\/span>\nstatic<\/span> <\/span>Student<\/span> <\/span>getOlderStudent<\/span>(<\/span>Student<\/span> <\/span>s1<\/span>, <\/span>Student<\/span> <\/span>s2<\/span>)<\/span><\/span>\n{<\/span><\/span>\n    <\/span>return<\/span> <\/span>s1<\/span>.<\/span>IsOlder<\/span>(s2) ? s1 : s2;<\/span><\/span>\n}<\/span><\/span>\n<\/span>\nint<\/span> <\/span>main<\/span>(<\/span>int<\/span> <\/span>argc<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span> <\/span>argv<\/span>[])<\/span><\/span>\n{<\/span><\/span>\n  Student <\/span>s1<\/span>(<\/span>"Fred Bloggs"<\/span>, <\/span>"56 Main St., Anytown, USA"<\/span>, <\/span>23<\/span>,<\/span><\/span>\n             <\/span>"Yale"<\/span>, <\/span>"New Haven, CT"<\/span>);<\/span><\/span>\n  Student <\/span>s2<\/span>(<\/span>"Mary Jones"<\/span>, <\/span>"12 Canyon Court, Prime Real Estate, USA"<\/span>, <\/span>19<\/span>,<\/span><\/span>\n             <\/span>"Harvard"<\/span>, <\/span>"Cambridge, MA"<\/span>);<\/span><\/span>\n<\/span>\n  Student s3 = <\/span>getOlderStudent<\/span>(s1, s2);<\/span><\/span>\n<\/span>\n  <\/span>std<\/span>::cout << <\/span>"The Older student is:"<\/span> << <\/span>std<\/span>::endl;<\/span><\/span>\n  <\/span>s3<\/span>.<\/span>Print<\/span>();<\/span><\/span>\n<\/span>\n  <\/span>return<\/span> <\/span>0<\/span>;<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
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In this program:<\/p>\n\n\n\n
    \n
  1. How many times (total), when and why, are the Student<\/code><\/strong> constructors (which ones?) and destructor invoked?<\/li>\n\n\n\n
  2. How many times (total), when and why, are the Person<\/code><\/strong> constructors (which ones?) and destructor invoked?<\/li>\n\n\n\n
  3. How many times (total), when and why, are each of the MyString<\/code><\/strong> constructors (which ones?) and destructor invoked?<\/li>\n\n\n\n
  4. How can you improve these figures? (You should be able to improve these numbers significantly!)<\/li>\n<\/ol>\n\n\n\n
    \n
    Hint:<\/strong> From the start of the program to its end, what would you expect the relationship to be between the number of calls to a class constructor and the number of calls to the same class’s destructor?<\/p>\n<\/blockquote>\n\n\n\n
    Modify the program in student.cpp<\/strong><\/code> (not the classes!<\/em><\/strong>) to significantly reduce the number of member functions that are invoked, while still producing correct results.<\/p>\n\n\n\n
    \n
    Do not add to or remove any of the arguments in the getOlderStudent()<\/code><\/strong> function!<\/p>\n<\/blockquote>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
    “Smoke and Mirrors” Part 1: The Nothing Class Here’s a ‘useful’ class: … and here is a similarly useful program that uses it: Convince yourself that this program compiles without error, and executes without failure. Explain why. What did the C++ compiler do for you? Write a Nothing class that does exactly the same thing as the […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":29,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-32","page","type-page","status-publish","hentry"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/pages\/32","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/comments?post=32"}],"version-history":[{"count":3,"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/pages\/32\/revisions"}],"predecessor-version":[{"id":1688,"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/pages\/32\/revisions\/1688"}],"up":[{"embeddable":true,"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/pages\/29"}],"wp:attachment":[{"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/media?parent=32"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}