:: rot13.btm -- Do ROT13 translation

setlocal
unset /q ch

iff %1.==. then
	echo usage: %0 file_to_rot13.txt
	quit 1
else
	set fp$=%@fileopen[%1,read]
	iff %fp$ == -1 then
		echo rot13.btm: error opening file %1
		quit 2
	endiff
endiff

setdos /x-45678

do forever
	set ch=%@ascii[%@fileread[%fp$,1]]
	if %@len[%ch] gt 3 leave
	iff %ch == 10 then
		echo.
	else
		iff (%ch ge 65 .and. %ch le 77) .or. (%ch ge 97 .and. %ch le 109) then
			set ch=%@eval[%ch + 13]
		elseiff (%ch ge 78 .and. %ch le 90) .or. (%ch ge 110 .and. %ch le 122) then
			set ch=%@eval[%ch - 13]
		endiff
		echos %@char[%ch]
	endiff
enddo

setdos /x0
set fp$=%@fileclose[%fp$]