loopsg.f

C  Author:   Mitch Richling<http://www.mitchr.me/>
C  IP:       Copyright 1993 by Mitch Richling.  All rights reserved.
C  Key word: FORTRAN f77 do
C  Notes:    Illustrates two common goto replacements for
C            repeat-until (do-while) and while-do type
C            loops.  This kind of thing is still commonly
C            found in working code.  

C             LOOPS with Goto
      program loopsg

      real X

      write (*,*) 'Typical "while-do" loop idiom.'
      X = 5
100   if (X .ge. 2) then
        write (*,*) 'X=', X
        X = X - 1
        goto 100
      endif 

       write (*,*) 'This is a typical "do-while" construct.'
       X=5
 400   continue
       X = X - 1
       write (*,*) 'X=', X
       if (X .ge. 3) goto 400

       write (*,*) 'This is a typical "repeat-until" construct.'
       X=5
 500   continue
       X = X - 1
       write (*,*) 'X=', X
       if (X .le. 0) goto 550
       goto 500
 550   continue

       write (*,*) 'This is another typical "while-do" idiom'
       x=5
 600   if (X .le. 0) goto 650
       write (*,*) 'X=', X
       X = X - 1
       goto 600
 650   continue

       end