BINARY NUMBER and the DIGITS

[JohnNichols]

If I have a binary number 101010 - as a decimal number 42 - is there an easy FORTRAN function to convert to a binary number and then determine the order of 1 and 0's --

John

[Les_Neilson]

John

I'm not sure exactly what you mean. All numbers are stored internally as binary. You can use internal write to put the binary format of a number into a character string which you can print or process somehow.

If you want to test whether a particular bit is set or not you should look up BTEST in the help. The help also points to functions that allow the user to clear, set, or swap a particular bit.

Les

[andrew_4619]

for example

integer(4)      :: l1
character(32) :: gchar
write(gchar,'(B32.32)') l1

which would set the string to '00000000000000000000000000010001' if L1 was 17

[Steven_L_Intel1]

There's also the intrinsic function POPCNT which will tell you the number of 1 bits in a value. (see also LEADZ and TRAILZ.)

[JohnNichols]

program Console1

    implicit none
    character(6) :: gchar
    character :: a
    integer :: i = 2
    integer :: pos
    logical :: bool

    integer(4)      :: l1
    l1 = 17
    write(gchar,'(B6.6)') l1


    do pos=6,0,-1
        bool = btest(i, pos)
        if(bool .eq. .TRUE.) then
            print *, pos, 1
        else
            print *, pos, 0
        endif
    end do


    end program Console1

Explanation:

In structures a restraint point can have 6 degrees of - each freedom is either set or released ie 1 or 0 is the usual code.  One ends up with a file with every joint having 6 integers usually stored as integer a(6) - one ends up trying to remember binary codes.  Now AUTODESK has a neat function in AutoCAD for setting some switches - you pick a decimal - 1, 2, 4, 8 and it sets the switch - I was wondering as I developed Borr - see the long discussion top that now runs to 30 pages if printed - I did - if I could use a integer code 0- 63 to cover all the restraint options.  The answer is a resounding yes, but one needs a large case statement to step through the combinations - or look up the binary equivalent of the integer directly.  So now I can input a full restraint as a 63 and a free as 0, lot less typing and less likely to miss one.  The other common one is 111000 or 56.  I was not aware of the BTEST function and my INTEL install on the home computer does not give me a nice help system - a WINDOWS 10 upgrade appears to have played with it - no search no nothing,  so I asked.

This code is great - thanks

John

[jimdempseyatthecove]

By the use of a binary bit field, you imply that multiple bits can be set. Therefor you would not have a select case, but rather you would have a filter.

if(bitest(Mask, 0)) call DoWork0()
if(bitest(Mask, 1)) call DoWork1()
...

However note you can create an array of function pointers, and note, if each DoWork can run independently, you could parallelize the code

!$omp parallel do schedule(dynamic, 1)
do i=1,64
  if(btest(Mask, i)) FunctionPointerArray(i)%DoWork()
end do

Jim Dempsey