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Dec 19th, 2008

Manipulators

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Hi i am trying to understand manipulators. Can someone explain what is happening here

C++ Syntax (Toggle Plain Text)
 for (int i = 0; i < n; i++) {
        cout << setiosflags(ios::left) << setw(15) << item[i]
             << setw(8) << setprecision(0) << code[i]
             << setiosflags(ios::right) << setw(8) << setprecision(2)
             << setiosflags(ios::fixed | ios::showpoint) << cost[i] 
             << endl;
    }
 for (int i = 0; i < n; i++) {
        cout << setiosflags(ios::left) << setw(15) << item[i]
             << setw(8) << setprecision(0) << code[i]
             << setiosflags(ios::right) << setw(8) << setprecision(2)
             << setiosflags(ios::fixed | ios::showpoint) << cost[i] 
             << endl;
    }

For the first time, i mean in the first iteration of the loop, it prints correctly but from the second iteration, the output always seems to be right justified. Why?

Here is the output of the above loop

C++ Syntax (Toggle Plain Text)
dsjfh          102        32.32
        jdshfjd     120 1212.00
       dfdsfdsf     322   32.23
dsjfh          102        32.32
        jdshfjd     120 1212.00
       dfdsfdsf     322   32.23

Last edited by sweeya; Dec 19th, 2008 at 4:16 am.

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sweeya

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Dec 19th, 2008

Re: Manipulators

The short answer is that ios::left and ios::right (and some others) are not mutually exclusive, but your code reflects an assumption that they are. It is possible to have both set simultaneously and, of so, it is up to the implementation to decide which one (or a combination) applies.

Try using resetiosflags() manipulators to restore the various flags to their defaults before each line of output.

grumpier

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Dec 19th, 2008

Re: Manipulators

Hi,
Thanks, using resetiosflags worked. I was under the impression that they are mutually exclusive. Anyways, how is it working for the first one correctly?(just want to understand what is happening)

sweeya

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Dec 19th, 2008

Re: Manipulators

Define your own manipulators, make a code simpler:
http://www.java2s.com/Tutorial/Cpp/0...anipulator.htm

ArkM

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Dec 19th, 2008

Re: Manipulators

Click to Expand / Collapse Quote originally posted by sweeya ...

Hi,
Thanks, using resetiosflags worked. I was under the impression that they are mutually exclusive. Anyways, how is it working for the first one correctly?(just want to understand what is happening)

On the first loop iteration, the stream flags are set to defaults. That is not true for subsequent iterations.

grumpier

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