commit - 2b2bebb21a0f7fe854a1a4647057b51ff5ce279d
commit + 6572a112c021fe35a53621b97498ef3e0538f633
blob - /dev/null
blob + 85a97faf5bea66ea8bb8f4068c3d01bc8d9a5bad (mode 644)
--- /dev/null
+++ examples/rot13.bf
+-,+[ Read first character and start outer character reading loop
+ -[ Skip forward if character is 0
+ >>++++[>++++++++<-] Set up divisor (32) for division loop
+ (MEMORY LAYOUT: dividend copy remainder divisor quotient zero zero)
+ <+<-[ Set up dividend (x minus 1) and enter division loop
+ >+>+>-[>>>] Increase copy and remainder / reduce divisor / Normal case: skip forward
+ <[[>+<-]>>+>] Special case: move remainder back to divisor and increase quotient
+ <<<<<- Decrement dividend
+ ] End division loop
+ ]>>>[-]+ End skip loop; zero former divisor and reuse space for a flag
+ >--[-[<->+++[-]]]<[ Zero that flag unless quotient was 2 or 3; zero quotient; check flag
+ ++++++++++++<[ If flag then set up divisor (13) for second division loop
+ (MEMORY LAYOUT: zero copy dividend divisor remainder quotient zero zero)
+ >-[>+>>] Reduce divisor; Normal case: increase remainder
+ >[+[<+>-]>+>>] Special case: increase remainder / move it back to divisor / increase quotient
+ <<<<<- Decrease dividend
+ ] End division loop
+ >>[<+>-] Add remainder back to divisor to get a useful 13
+ >[ Skip forward if quotient was 0
+ -[ Decrement quotient and skip forward if quotient was 1
+ -<<[-]>> Zero quotient and divisor if quotient was 2
+ ]<<[<<->>-]>> Zero divisor and subtract 13 from copy if quotient was 1
+ ]<<[<<+>>-] Zero divisor and add 13 to copy if quotient was 0
+ ] End outer skip loop (jump to here if ((character minus 1)/32) was not 2 or 3)
+ <[-] Clear remainder from first division if second division was skipped
+ <.[-] Output ROT13ed character from copy and clear it
+ <-,+ Read next character
+] End character reading loop