C Language, Newbie Question: using delete with dynamic 2-d arrays

Newbie Question: using delete with dynamic 2-d arrays

Author	Message
Jack Kle #1 / 7	Newbie Question: using delete with dynamic 2-d arrays On Thu, 22 Apr 1999 02:13:13 GMT, Chirag Mehta Quote: > Hello, > I have been looking for an answer to this one, and have yet to find it. > Perhaps someone out there can help. I am trying to figure out how to > use "delete" to free up a dynamically created two dimensional array. > Here's the code I use to create the array: > //Dynamically create array of length variable > int *array = new int [variable]; > for (int s = 0; s < variable; s++) { > array[s] = new int[variable]; > } > This I understand, no problem, an array of pointers each pointing to an array. > Is this the correct way to delete array? > //Delete the dynamically created memory > for(s = 0; s < variable; s++) { > delete [] array[s]; > } > delete array; > Thanks for the help. > ---------- > Chirag Mehta > (909) 237-3008 <Jack> The correct way is to ask in comp.lang.c++, not in comp.lang.c. But the correct way is to have one delete [] for each new [], and in reverse order. </Jack> -- Do not email me with questions about programming. Post them to the appropriate newsgroup. Followups to my posts are welcome.
Mon, 08 Oct 2001 03:00:00 GMT

Martin Ambuh #2 / 7	Newbie Question: using delete with dynamic 2-d arrays Quote: > Hello, > I have been looking for an answer to this one, and have yet to find it. > Perhaps someone out there can help. I am trying to figure out how to > use "delete" to free up a dynamically created two dimensional array. You don't. You use free() to delete dynamically allocated memory. delete (and delete[] and new) are C++, not C. This different language is either. Lisp and Scheme are OK, but only as part of jokes. Quote: > Here's the code I use to create the array: > //Dynamically create array of length variable > int *array = new int [variable]; > for (int s = 0; s < variable; s++) { > array[s] = new int[variable]; > } > This I understand, no problem, an array of pointers each pointing to an array. Plenty of problem. 'new' is an undefined identifier. Quote: > Is this the correct way to delete array? No. Quote: > //Delete the dynamically created memory > for(s = 0; s < variable; s++) { > delete [] array[s]; > } > delete array; --
Mon, 08 Oct 2001 03:00:00 GMT

David Star #3 / 7	Newbie Question: using delete with dynamic 2-d arrays (off topic) Quote: >On Thu, 22 Apr 1999 02:13:13 GMT, Chirag Mehta [snip] >> Is this the correct way to delete array? [snip] >The correct way is to ask in comp.lang.c++, not in comp.lang.c. But >the correct way is to have one delete [] for each new [], and in >reverse order. "in reverse order"? Am I missing something here? -dave -- ------------------------------------------------------------------------ * Remember to remove the spam blocker when replying. * Return address is: dstarr AT xnet DOT com ------------------------------------------------------------------------
Tue, 09 Oct 2001 03:00:00 GMT

Ari Lukumie #4 / 7	Newbie Question: using delete with dynamic 2-d arrays Quote: > (off topic) > >On Thu, 22 Apr 1999 02:13:13 GMT, Chirag Mehta > [snip] > >> Is this the correct way to delete array? > [snip] > >The correct way is to ask in comp.lang.c++, not in comp.lang.c. But > >the correct way is to have one delete [] for each new [], and in > >reverse order. > "in reverse order"? Am I missing something here? <further off-topic> If you use delete[] on an object it must have been allocated with new[], not with new. For example: char p = new char(10); delete [] p; // error char p = new char[10]; delete p; // error char p = new char(10); delete p; // ok char p = new char[10]; delete [] p; // ok (What 'new char(10)' means is left as an excercise for the reader :) </further off-topic> AriL -- Humans may send email (if absolutely necessary) to the obvious non-spam address.
Tue, 09 Oct 2001 03:00:00 GMT

David Star #5 / 7	Newbie Question: using delete with dynamic 2-d arrays <yet more off-topic> Quote: >> (off topic) Quote: >> >On Thu, 22 Apr 1999 02:13:13 GMT, Chirag Mehta >> [snip] >> >> Is this the correct way to delete array? >> [snip] >> >The correct way is to ask in comp.lang.c++, not in comp.lang.c. But >> >the correct way is to have one delete [] for each new [], and in >> >reverse order. >> "in reverse order"? Am I missing something here? ><further off-topic> >If you use delete[] on an object it must have been allocated with new[], >not with new. For example: [snip] What my question actually was meant to address was that JK's post could easily be interpreted to mean that new[] and delete[] must be matched in some sort of LIFO way, i.e.: char p = new char[x]; char q = new char[y]; delete [] q; delete [] p; where q /has/ to be deleted before p. While the C++ committee has created such a monstrosity that I might have missed this little nugget about "in reverse order" re new and delete, I think the sentence only inadvertently gives this impression. My question was actually rhetorical, to give JK an opportunity to clarify the sentence. Sorry about the further off-topic posting, but enough people read this newsgroup that the issue needed to be clarified. I believe this is especially important when it arises from a post by someone like JK, who is normally quite clear in his posts. In retrospect, an ambiguous rhetorical question is not really the best way to address a (perceived) lack of clarity in a post :) -dave -- ------------------------------------------------------------------------ * Remember to remove the spam blocker when replying. * Return address is: dstarr AT xnet DOT com ------------------------------------------------------------------------
Tue, 09 Oct 2001 03:00:00 GMT

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