rigorously predictable random numbers

[Ray Andrews <rayandrews@xxxxxxxxxxx>]

    #!/usr/bin/zsh
      
      echo $RANDOM
      var=$( echo $RANDOM )
      echo $var
      
      ... I run that and get:
      
      
      
      3 /aWorking/Zsh/Source/Wk 1 % . test1
      23008
      3809
      
      3 /aWorking/Zsh/Source/Wk 1 % . test1
      3809
      768
      
      3 /aWorking/Zsh/Source/Wk 1 % . test1
      768
      11071
      
      3 /aWorking/Zsh/Source/Wk 1 % . test1
      11071
      26432
      
      3 /aWorking/Zsh/Source/Wk 1 % . test1
      26432
      19059
      
      3 /aWorking/Zsh/Source/Wk 1 % . test1
      19059
      14427
      
      ... the result of the first $RANDOM is always exactly the result
      of the second $RANDOM in the previous call to the script.  This
      might not be as unexpected in a function where at least it's the
      same shell, but a script, seems to me, should always have a
      virginal notion of $RANDOM, no?  Yet it remembers the previous
      result from another shell.  I have the vaguest fragment of memory
      that we discussed this on the list once before.