BETWEEN

WITHIN  was meant to replace  BETWEEN  but it hasn't always
been a comfortable fit.

A characteristic of  WITHIN  is that the upper limit is not included
in the range.  This can lead to obfuscated code e.g.

    CHAR a   CHAR z  1+   WITHIN

Thus the functionality of  BETWEEN  is still being used, if not
the word itself.  When defined today, it is usually as:

: BETWEEN ( n1|u1 n2|u2 n3|u3 -- flag )   1+ WITHIN ;

But it is not without problem  e.g. it fails when  u1 =  u3  =  MAX-U .
Perhaps not so significant for 32-bit systems as for 16-bit, it is
nevertheless an inconsistency which can catch a programmer
unawares.

Playing with the algorithm for WITHIN (A.6.2.2440) one gets:

: BETWEEN  ( n1|u1 n2|u2 n3|u3 -- flag )   OVER - -ROT - U< 0= ;

It seems to work.  If anyone finds a problem or knows something
better, let us know.  In the meantime, here are several code versions.

code BETWEEN ( n1|u1 n2|u2 n3|u3 -- flag )
   sub ebx, 0 [ebp]
   mov ecx, 4 [ebp]
   sub ecx, 0 [ebp]
   cmp ebx, ecx
   sbb ebx, ebx
   not ebx
   lea ebp, 8 [ebp]
   ret
end-code

code BETWEEN ( n1|u1 n2|u2 n3|u3 -- flag )
   bx pop  ax pop  cx pop
   ax bx sub  ax cx sub  cx bx cmp
   bx bx sbb  bx not  bx push  next
end-code