REVERSE‐DIR - KVonGit/zil-stuff GitHub Wiki
<ROUTINE REVERSE-DIR (DIR)
<COND
(<==? .DIR ,P?NORTH> ,P?SOUTH)
(<==? .DIR ,P?SOUTH> ,P?NORTH)
(<==? .DIR ,P?EAST> ,P?WEST)
(<==? .DIR ,P?WEST> ,P?EAST)
(<==? .DIR ,P?UP> ,P?DOWN)
(<==? .DIR ,P?DOWN> ,P?UP)
(T ,P?NOWHERE)
>
>