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Hi friends,
I tried out something like this which is given below in VC++ by referring Dennis M. Ritchie (ANSI C second edition) book examples.
struct Key *low = &tab[0];
struct Key *high = &tab[n];
struct Key *mid;
mid = low + (high-low) / 2; // Error: cannot convert from 'int' to 'struct Key *'
My question is how they are using this expression mid = low + (high-low) / 2;?. I don't know whether I misunderstood the concept or there is some difference between ANSI C and VC++. Please anyone help me in this.
Regards,
S.Shanmuga Raja
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Which compiler gives the error? I just tried this with Visual Studio 2010 C++ compiler and it compiles correctly, as it should, in both .c and .cpp versions.
Veni, vidi, abiit domum
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There is a difference between ANSI C, some other C++ compilers, and what Visual Studio allows for pointer arithmetic.
Pointer arithmetic is not allowed on all platforms, as least not allowed the way you have it. There is a ptrdiff_t macro that allows taking pointer differences on many platforms, but I'm not sure whether that is allowed in ANSI C or not. In any event, that is not what you need.
Some compilers will let you cast a pointer to be type size_t, however, that is not portable across all platforms and compilers and is generally not a good practice.
Presumably, the array tab is defined to be an array of Key structures:
So, to write portable code, write code something like this:
int BinarySearch(int low, int high, struct Key x)
{
int index = -1;
int mid = 0;
while (low <= high)
{
mid = (low + high) >> 1;
if (firstKeyLessThanSecondKey(x, tab[mid]))
{
high = mid - 1;
}
else if (firstKeyLessThanSecondKey(tab[mid], x))
{
low = mid + 1;
}
else
{
index = mid;
}
}
return index;
}
To search the entire tab array for a Key equal to x, pass 0 for low and the array length minus 1 for high.
This will return -1 if the Key that matches x is not found, otherwise the index into the array tab for the key that matches x will be returned.
Because the values of low and high are always positive, a shift can be used for the divide by 2.
mid = (low + high) >> 1;
Of course, you'll have to modify this code for your application. I made some assumptions based on the book you cited.
Also, if the Key structure isn't very small, then instead of passing the Key structure by value, you might want to pass a pointer to a Key to both the BinarySearch function and to the FirstKeyLessThanSecondKey function.
Finally, I didn't compile and test this. I'm never 100% sure if code is correct until I debug it under varied conditions. If not correct, I expect this is very close to correct.
modified 2-Nov-13 0:51am.
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The MSDN says if you you return TRUE from LVN_EndLabelEdit notification, the control will accept the new edited text.
It's not true for my experiments.
I tried return TRUE, it didn't work, the label stays unchanged.
...
BOOL OnEndLabelEidt( ..., LPNMLVDISPINFO pDispInfo)
{
return TRUE ; // doesn't work
// so I have to do it manually
LVITEM item ;
...
item.pszText = pDisInfo->item.pszText ;
ListView_SetItem(hListview, &item ) ; // then it works
}
As it isn't TRUE for any other notfications.
such as TreeView::TVN_EndEditLabel.
TreeView::TVN_EXPANDING returns TRUE expands the node anyway, which conflicts with the Documentation either.
Could someone give me a clue? Thanks.
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If you think the documentation is wrong then you should report it to Microsoft.
Veni, vidi, abiit domum
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I am confused. I think there must be something wrong in my comprehension,
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<pre lang="cs">void Test::OnDrawSortArrow(CDC* pDC, CRect rectArrow)
{
Metafile * emf = NULL;
emf = LoadMetafile(IDR_ICON_EXPAND, NULL, true);
Gdiplus::Bitmap* image = BitmapFromEmf(emf, 8, 8, Color(255,82,82,82), 0);
HICON hIcon = NULL;
if(IsAscending())
image->RotateFlip(Rotate180FlipNone);
image->GetHICON(&hIcon);
pDC->DrawIcon(rectArrow.TopLeft().x - 20, rectArrow.TopLeft().y - 10, hIcon);
delete emf;
}</pre>
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This recursive function doesnt have a end point,becuase 12 item is not exist in the array.How we can fix this recursive function to solve this problem?
int _tmain(int argc, _TCHAR* argv[])
{
int arr[10] = {1,2,3,4,5,6,7,8,9,10};
int sum;
sum=BinSearch(arr,12,0,9);
cout<<sum;
return 0;
}
int BinSearch(int A[],int item,int low,int height)
{
int mid;
mid=(low+height)/2;
if(A[mid]==item)
return mid;
else if(item > A[mid])
return Binary_Search(A,item,mid+1,height);
else
return Binary_Search(A,item,low,mid-1);
}
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Add as 1st line in BinSearch:
if(low > height)return -1; // Return 'not found' code
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The array passed into the function could potentially have any value in it you can't select a simple return value to represent your error condition. I'd consider throwing an exception rather than using a return value:
if( A[low] > item || A[high] < item] ) throw binary_search_out_of_bounds();
Another option is to have the function return a std::pair<bool, int> where the first item in the pair tells the caller if they have an error condition or not and the second is the value they're after. Personally I find that a bit ugly and it complicates your code more as you have to do more in the calling function so I'd go with an exception.
Cheers,
Ash
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Is it safe to send a POSITION variable throgh wParam (First parameter on a SendMessage)? Thank you.
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It is safe to send. The POSITION type is a pointer that can be passed as WPARAM or LPARAM. But you must ensure that the object referenced by the pointer still exists when handling the message.
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Of course that I'll ensure that POSITION variable send it through wParam is valid.
POSITION pos = (POSITION)wParam;
if(NULL != pos)
{
ItemData* pData = (ItemData*)m_ItemDataList.GetAt(pos);
if(NULL != pData)
{
m_ItemDataList.RemoveAt(pos);
delete pData;
}
}
Thank you for your attention.
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good day all ..
i need only to get any voltage out from my laptop to control a relay
how to get a signal from a LAN port from any pin ?
in my laptop there is no com Port or lpt Port
also the usb port needs interfacing circuits which is not nessesary
in my simple project ... thats why i choosed the LAN Port
i use (visual basic 6) .. any help would much appriciated .
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coolerfantasy wrote: i use (visual basic 6)
So why are you posting in the C++ forum?
In any case you need to research how signals are presented on LAN ports, which is a hardware issue.
Veni, vidi, abiit domum
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you are right
i will repost in the vb forum .
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As I said before this is a hardware issue, not a programming one.
Veni, vidi, abiit domum
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I wanted to verify if I am right on this question for college class.
#6. Write a single statement that assigns the values 99, 100 and 88 to an integer array named TestScores. Use the C++ notation used for the “lotterynumbers” array. (4 points)
I came up with...
int TestScores[5];
TestScores[0] = 99;
TestScores[1] = 100;
TestScores[2] = 88;
Correct me if I am wrong 
Thank you.
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That's not a single statement.
Veni, vidi, vici.
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That are in effect 4 statements.
You might want to read this: Initializing Aggregates[^].
What you are looking for is:
int TestScores[5] = { 99, 100, 88 };
Note that the remaining elements of the array are initialized with zero, so that the following is the same as the previous statement.
int TestScores[5] = { 99, 100, 88, 0, 0 };
0100000101101110011001000111001010000010
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Thank you! I understand what I did wrong... i needed a single statement, not a multiple statement.
Thanks again.
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