/usr/web/sources/contrib/fgb/root/sys/src/cmd/4th/lib/rot13.4th

Plan 9 from Bell Labs’s /usr/web/sources/contrib/fgb/root/sys/src/cmd/4th/lib/rot13.4th


\ Taken from http://en.literateprograms.org/Rot13_(Forth)
\ Optimized for 4tH by J.L. Bezemer, 2007/2008

[UNDEFINED] within [IF]
include lib/range.4th
[THEN]

[UNDEFINED] rot13 [IF]
: rot13                                ( c -- o )
  dup bl or dup [char] a [char] z 1 [+] within
  if [char] m > 13 swap if negate then + else drop then
;
[THEN]

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