6.1.0300
1-
one-minus
CORE
 
( n1 | u1 -- n2 | u2 )

Subtract one (1) from n1 | u1 giving the difference n2 | u2.

Testing:
T{          2 1- ->        1 }T
T{          1 1- ->        0 }T
T{          0 1- ->       -1 }T
T{ MID-UINT+1 1- -> MID-UINT }T