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POfunction modifies a class not referenced
primarykey
Id
11245136
data
AcceptedAnswerId
11245308
AnswerCount
3
ClosedDate
CommentCount
1
CommunityOwnedDate
CreationDate
2012-06-28T12:54:52.777
FavoriteCount
0
LastActivityDate
2012-06-28T13:04:48.573
LastEditDate
LastEditorUserId
0
OwnerUserId
1485929
ParentId
0
PostTypeId
1
Score
1
ViewCount
78
LastEditorDisplayName
text
Body
<p>I am experimenting with a linked list. My function "null" seems to modify my list even though the list is not passed by reference. I've read that these problems can occur with objects that are passed as normal call-by-value parameter and that it is one the reasons that data inside a class is not declared as an public member in good OOP. I have tried the null function as an member function of the list and it works fine, but I still would like to understand why this way doesn't work properly. Thanks</p> <pre><code>#include <iostream> #include <new> #include <time.h> #include <stdlib.h> using namespace std; class list{ public: struct element { int data; element* next; }; element * head; list(){ head=NULL; } ~list(){ while (head!=NULL){ element *e = head->next; delete head; head = e; } cout<<"Destructing..\n"; } void add (int value){ element *e = new element; e->data = value; e->next = head; head= e; } }; void fill10 (class list & l){ for (int i= 0; i<10 ;i++){ l.add((rand()%10)+1); } } bool null (class list l){ if (l.head!=NULL){ return false;} return true; } int main () { srand(time(NULL)); class list l; fill10(l); cout<<l.head->data<<endl; cout<<l.head<<endl; cout<<endl<<null(l)<<endl;//when I comment this everything works out as expected cout<<l.head->data<<endl; //this data is not the same anymore after null is called cout<<l.head<<endl; return 0; } </code></pre>
Tags
<c++><class>
Title
function modifies a class not referenced
singulars
PostAcceptedAnswerId
1. PO
  singulars
  PostTypePostTypeId
  PTAnswer
PostParentId
1. This table or related slice is empty.
PostTypePostTypeId
1. PTQuestion
UserLastEditorUserId
1. This table or related slice is empty.
UserOwnerUserId
1. USrex123
plurals
PostLinksPostIdRelatedPostId
1. PL
  singulars
  LinkTypeLinkTypeId
  LTLinked
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. This table or related slice is empty.
PostsParentIdCreationDate
1. PO
  singulars
  PostTypePostTypeId
  PTAnswer
2. PO
  singulars
  PostTypePostTypeId
  PTAnswer
3. PO
  singulars
  PostTypePostTypeId
  PTAnswer
VotesPostIdCreationDate
1. VO
  singulars
  PostPostId
  POfunction modifies a class not referenced
  UserUserId
  This table or related slice is empty.
  VoteTypeVoteTypeId
  VTUpMod
CommentsPostId
1. COYou should fix the indentation, it makes the code confusing
  singulars
  PostPostId
  POfunction modifies a class not referenced
  UserUserId
  USDavid Rodríguez - dribeas

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