Command to pad zeros to specific locations in binary numbers?

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孤独总比滥情好
孤独总比滥情好 2021-01-07 02:48

I need to pad zeros to specific locations in binary numbers. Looping the array form of a binary number such as dec2bin(43) and adding the zeros and adjusting th

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  •  我在风中等你
    2021-01-07 03:54

    Race begins! Mendo wins, gevang is a good second, thewaywewalk is the third and jaheruddin comes in fourth. The Shai's bitshifting is implemented in the shai function, unfortunately not yet getting it run faster.

    Results

    gevang :2.2e-05
    thewaywewalk :5.6975e-05
    mendo :2.2102e-05
    jaheruddin :0.0001693
    shai (poor hhh-implementation) 5.3288e-04
    

    Warmed-up testing of the answers

    function test_padding_zeros()
    
        function myOutput=gevang(xx,positions)
            nPads = length(positions);
            nPadsShifts = 1:nPads;
            myOutput = ones(1, length(xx) + nPads); % re-indexing on the new array
            myOutput(positions + nPadsShifts) = 0;  % padding values
            myOutput(myOutput==1) = xx;                    % set original bit values
        end
    
        function myOutput=thewaywewalk(x,positions)
            idx = numel(x):-1:1;
            myOutput = num2cell(x);
            myOutput(2,idx(positions)) = {0};
            myOutput = [myOutput{:}];
        end
    
        function myOutput=jaheruddin(myInput,positions) % myInput can be a row vector or a matrix!
            n = size(myInput,2)+numel(positions);
            myOutput = false(size(myInput,1),n);
            myOutput(:,setxor((1:length(positions)),1:n))=myInput;
        end
    
        function myOutput=mendo(myInput,positions)
            myOutput = ones(1,length(myInput)+length(positions));
            myOutput(positions+(1:length(positions))) = 0;
            myOutput(myOutput==1) = myInput;
        end
    
        function out = bizarreBitShift( bNum, fromBit, shiftAmount )
            % construct a mask
            msk = uint32( (2^( fromBit - 1 ) )-1 ); 
            shiftPart = bitand( uint32(bNum), bitcmp(msk) ); % bitcmp - complement of bits
            staticPart = bitand( uint32(bNum), msk );
            out = bitshift( shiftPart , shiftAmount );
            out = bitor( out, staticPart );
        end
    
        function myOutput=shai(myInput,positions)
            shiftAmount=1;
            myOutput=sprintf('%d',myInput);
            myOutput=bin2dec(myOutput);
            k=0;
            for ii=1:length(positions)
                fromBit=positions(ii)+k;
                myOutput=bizarreBitShift(myOutput, fromBit, shiftAmount);
                k=k+1;
            end
    
            myOutput=ismember(dec2bin(myOutput),'1');
        end
    
    
    
    
    positions = [1 3 6]; %// example data
    myInput = [1 0 1 0 1 1]; %// example data
    
    ggevang=@() gevang(myInput,positions);
    tthewaywewalk=@() thewaywewalk(myInput,positions);
    mmendo=@() mendo(myInput,positions);
    jjaheruddin=@() jaheruddin(myInput,positions);
    sshai=@() shai(myInput,positions);
    
    timeit(ggevang)
    timeit(tthewaywewalk)
    timeit(mmendo)
    timeit(jjaheruddin)
    timeit(sshai)
    
    end
    

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