(
n --
d )
Convert the number
n to the double-cell number
d
with the same numerical value.
Testing:
T{ 0 S>D -> 0 0 }T
T{ 1 S>D -> 1 0 }T
T{ 2 S>D -> 2 0 }T
T{ -1 S>D -> -1 -1 }T
T{ -2 S>D -> -2 -1 }T
T{ MIN-INT S>D -> MIN-INT -1 }T
T{ MAX-INT S>D -> MAX-INT 0 }T