C++ Tutorial
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Off Topic C++ TutorialAnd I have edited Lee's to make mine store the data.
Edit this is similar to above except it writes the data to a file and instead of opening text2.txt it opens text2.txt.txt how to fix?
<removed source> nvm I fixed it, but it leaves a ÿ at the end of the file
Edit nvm I fixed it
I really need a command that works as table.insert with dynamic memory is there a way or a function?
edited 4×, last 22.07.10 06:01:30 am
Otherwise you would have to use pointers:
You have to create a new pointer that points to a bigger array, you copy the old content, add the new one, delete the old pointer and make it point to the new one.
BTW: Your code is a mess, try to make it look more or less like this:
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if (condition)
{
while(condition)
{
dostuff();
}
}
That way you can comment out lines like if (condition) easier without having to comment out the braces, which may turn into a headache if your project gets bigger.
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(sizeof yourarray)/sizeof(yourtype)
The sizeof operator returns the size in bytes, so you divide it and get the value.
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int* a = new int[4]; cout << (sizeof a/sizeof(int));
Yes you have to loop through and assign the new value
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for(int i=0; i<oldsize; i++)
{
newarray [i] = oldarray[i];
}
But it should return a char* or wathever type you are using, still, you need to know the size of the old array because "sizeofing" pointers always returns 4 (pointers point to memory addresses so they use 4 bytes atleast in my 32-bit windows).
BTW, you might want to read on typecasting: http://www.cplusplus.com/doc/tutorial/typecasting/
This example concatenates a c string to another one
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#include <cstdlib>
#include <iostream>
using namespace std;
char he[] = "he"; // 'h','e',0
char* concatenate(char* oldstr, char* addstr, int sizeofold, int sizeofadd)
{
char* newstr = new char[sizeofold + sizeofadd];
for(int i=0; i<sizeofold; i++)
{
newstr[i] = oldstr[i];
}
for(int i=0; i< sizeofadd; i++)
{
//here we overwrote the null character from the old string, if we were using other type
//for something different we would have declared int i=1.
newstr[i+sizeofold] = addstr[i];
}
newstr[sizeofold + sizeofadd] = 0; //We add again the terminating null character
return newstr;
}
int main(int argc, char *argv[])
{
cout << concatenate(he, "llo dude", 2,8) << '\n';
system("PAUSE");
return EXIT_SUCCESS;
}
I'd recommend you to use vectors since they support different types and and have less bugs than my code
http://www.cplusplus.com/reference/stl/vector/
edited 1×, last 22.07.10 08:00:39 am
Do not re-write or fix just tell me what is wrong.
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#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <new>
using namespace std;
int main() {
while (true) {
stringstream data;
string* file_data;
string input("text.txt");
int l(0);
cout << "Enter a file to copy: ";
getline(cin, input);
if (input == "exit")
break;
ifstream file (input);
if (file.is_open()){
while (!file.eof())
data << (char) file.get();
file_data = new (nothrow) string[l];
file_data[l] = data.str();
l++;
file.close();
}
else cout << "Error: Can not open the file: \""+input+"\".";
ofstream file2;
string filename("");
for ( int i = 0; i<input.length(); i++ )
if ( input.substr(i,i) != "." )
filename = filename+input.substr(i,i);
else
filename = filename+" (copy).";
file2.open(filename);
int i(0);
for ( i = 0; i<l; i++)
if ( i < l-1 )
file2 << file_data[i] << endl;
else
file2 << file_data[i].substr(0,file_data[i].length()-1);
file2.close();
}
return 0;
}
It looks like ifstream doesn't support C++ strings, only the C ones.
Edit:
The name gets screwed up. text.txt becomes extt.t.txttxtxtt, but the correct data is written to the file.
Edit:
I am guessing it is impossible to return arrays? This won't work it stops at return na;
edited 3×, last 23.07.10 07:42:36 am
@filename
Assuming that you've done all of the proper changes with string to c string, apply the following patch:
Replace
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for ( int i = 0; i<input.length(); i++ ) if ( input.substr(i,i) != "." ) filename = filename+input.substr(i,i); else filename = filename+" (copy).";
with the following
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int dot = filename.find(".");
if (dot != filename.npos)
filename.replace(dot,1,".copy.");
else
filename += ".copy";
And then change it according to your preferences.
Glad to see that you're making so much progress within such a short interval of time. Keep it up and it'll become second nature after a short while.
Edit:
How can a create a textarea a window and add text to that textarea? Or where can I learn GUI programming?
edited 2×, last 24.07.10 09:47:40 pm
However, GTK+ is not so big.
You can download the pack if you are running Dev-C++ by clicking the 'Tools' tab and then in 'Check for updates/packages', select devpaks.org as your devpak server and click on the 'Check for updates' button.
Once your Dev has loaded all the paks mark the pak named 'GTK (the gimp toolkit)' and click on download selected.
Then it will start to download the pack and install it, they usually include examples and tutorials.
You might also be interested in taking a look to this tutorial:
http://library.gnome.org/devel/gtk-tutorial/2.21/
http://ftp.gnome.org/pub/gnome/binaries/win32/gtk+/2.20/gtk+-bundle_2.20.0-20100406_win32.zip
Edit: Forget what I said, I will set it up in my PC first so I can give you better instructions, the GTK library seems to use many other libraries, too many.
Edit once again:
Ok, this is what you have to do:
Download the file I posted.
Uncompress all the files in C:\GTK
Download this template I made so we won't have to rewrite all the include directories which is an epic pain in the ass: http://www.mediafire.com/?g339useqgbhkhne
Open Dev-C++, go to File->New->Project->'GUI' tab->GTK project->Compile->Run
This is what we've got until now, don't expect much more:
http://img571.imageshack.us/img571/7668/dibujolem.png
It gives us a nice little resizeable window with buttons and a console that all it seems to do is throw weird warnings when we rightclick our project in the taskbar.
->If it comes out that you're not able to use your C:, open the .template file with notepad and replace every C:\GTK with D:\GTK or whatever.
edited 2×, last 25.07.10 12:51:25 pm
I tried returning a pointer again, but it still fails.
Here's an example that inserts a number if it's odd else 0:
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#include <iostream>
using namespace std;
int* add(int* list, int* ssize){
*ssize += 1;
if(!(list = (int* )realloc(list,sizeof(int)*(*ssize))))
cout << "Failed to reallocate memory\n";
list[*ssize-1] = (*ssize)*((*ssize)&1);
return list;
}
int main(){
int* list = NULL;
int ssize = 0;
for(int i=0;i<100;i++) list = add(list,&ssize);
for (int i=0;i<ssize;i++) cout << i << " " << list[i] << endl;
return 0;
}
This is the most important line:
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if(!(list = (int* )realloc(list,sizeof(int)*(*ssize)))) cout << "Failed to reallocate memory\n";
We defined list as a int* initialized to null. Note the distinction between a flat out pointer and an array:
A pointer defined as <type>* identifier is a variable pointer. This means that its address can be changed.
An array defined by <type> identifier[] is a constant pointer. This means that its address cannot be changed, but which doesn't mean that the content of the address cannot be changed.
Now here's the tricky part about this, we could have actually passed list as a reference like ssize into an void add(int** list, int* ssize); But we must then allocate both the container and the container's container in order for this to work. Since references are consts, we have to somehow cast it into a variable pointer (which in turn makes it lose its reference) so for brevity's sake, we just reassign the value of the list as the return value of the function add.
Some other oddities:
We could've also write this:
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int* add(int* list, int* ssize){
int size = (*ssize += 1);
if(!(list = (int* )realloc(list,sizeof(int)*size)))
cout << "Failed to reallocate memory\n";
list[size-1] = size*(size&1);
return list;
}
As the the default operator= method for all native C++ objects are associative (implying that they return the left-value of the assignment)
Output:
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0 1 1 0 2 3 3 0 4 5 5 0 6 7 7 0 8 9 9 0 ...