How to print all possible unique bit masks of unsigned long long?

Question

Having an unsigned long long how to print it in form of its hex mask into std::string?

I tried to iterate over binary (values like 0001, 0010, 0100) mask:

std::stringstream str;
std::string result;
for (unsigned long long mask = 1; mask != 0; mask <<= 1) {
    str << mask;
    str >> result;
    std::cout << result << std::endl;
    str.flush();
}

yet I see only values == 1 (see live sample here).

So I wonder how to print all possible unique bit masks of unsigned long long?

so you just want those with exactly one bit set to 1, right? — kratenko, Mar 19 '13 at 11:12
@jrok: yes I am (after all that contain only one `1` while all other digits are `0` in binary representation) — DuckQueen, Mar 19 '13 at 11:12
This [less complex version](http://ideone.com/wKV7hu) works fine for me. — Kerrek SB, Mar 19 '13 at 11:13
@DuckQueen I didn't get it immediately, I thought you wanted to iterate over all possible values. Silly me :) — jrok, Mar 19 '13 at 12:05

score 1 · Accepted Answer · edited May 23 '17 at 11:50

1

You need to use str.clear(), not str.flush(). And see this for the hex part

edited May 23 '17 at 11:50

Community

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answered Mar 19 '13 at 11:14

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score 1 · Answer 2 · edited May 23 '17 at 12:21

Having an unsigned long long how to print it in form of its hex mask into std::string?

You need to use std::hex for printing numbers in hexadecimal base and also note that to reuse the stringstream object you actually need to clear its content by using str() method and also clear the error state flags by calling clear():

#include <iostream>
#include <sstream>

int main()
{
    std::stringstream str;
    std::string result;
    for (unsigned long long mask = 1; mask != 0; mask <<= 1)
    {
        // retrieve the string:
        str << std::hex << mask;
        str >> result;
        std::cout << result << std::endl;

        // clear the stringstream:
        str.clear();
        str.str(std::string());
    }
}

See How to reuse an ostringstream? :)

score 0 · Answer 3 · edited May 23 '17 at 11:50

0

every value of a unsigned long long is unique. so iterate over it and have a look at this question Is there a printf converter to print in binary format?

[Edit] Ah I see you only want values with one bit set. Ok do not iterate, shift through it.

edited May 23 '17 at 11:50

Community

1
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answered Mar 19 '13 at 11:14

Manuel Amstutz

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How to print all possible unique bit masks of unsigned long long?

3 Answers3