1 6572a112 2022-04-28 op -,+[                         Read first character and start outer character reading loop
 2 6572a112 2022-04-28 op     -[                       Skip forward if character is 0
 3 6572a112 2022-04-28 op         >>++++[>++++++++<-]  Set up divisor (32) for division loop
 4 6572a112 2022-04-28 op                                (MEMORY LAYOUT: dividend copy remainder divisor quotient zero zero)
 5 6572a112 2022-04-28 op         <+<-[                Set up dividend (x minus 1) and enter division loop
 6 6572a112 2022-04-28 op             >+>+>-[>>>]      Increase copy and remainder / reduce divisor / Normal case: skip forward
 7 6572a112 2022-04-28 op             <[[>+<-]>>+>]    Special case: move remainder back to divisor and increase quotient
 8 6572a112 2022-04-28 op             <<<<<-           Decrement dividend
 9 6572a112 2022-04-28 op         ]                    End division loop
10 6572a112 2022-04-28 op     ]>>>[-]+                 End skip loop; zero former divisor and reuse space for a flag
11 6572a112 2022-04-28 op     >--[-[<->+++[-]]]<[         Zero that flag unless quotient was 2 or 3; zero quotient; check flag
12 6572a112 2022-04-28 op         ++++++++++++<[       If flag then set up divisor (13) for second division loop
13 6572a112 2022-04-28 op                                (MEMORY LAYOUT: zero copy dividend divisor remainder quotient zero zero)
14 6572a112 2022-04-28 op             >-[>+>>]         Reduce divisor; Normal case: increase remainder
15 6572a112 2022-04-28 op             >[+[<+>-]>+>>]   Special case: increase remainder / move it back to divisor / increase quotient
16 6572a112 2022-04-28 op             <<<<<-           Decrease dividend
17 6572a112 2022-04-28 op         ]                    End division loop
18 6572a112 2022-04-28 op         >>[<+>-]             Add remainder back to divisor to get a useful 13
19 6572a112 2022-04-28 op         >[                   Skip forward if quotient was 0
20 6572a112 2022-04-28 op             -[               Decrement quotient and skip forward if quotient was 1
21 6572a112 2022-04-28 op                 -<<[-]>>     Zero quotient and divisor if quotient was 2
22 6572a112 2022-04-28 op             ]<<[<<->>-]>>    Zero divisor and subtract 13 from copy if quotient was 1
23 6572a112 2022-04-28 op         ]<<[<<+>>-]          Zero divisor and add 13 to copy if quotient was 0
24 6572a112 2022-04-28 op     ]                        End outer skip loop (jump to here if ((character minus 1)/32) was not 2 or 3)
25 6572a112 2022-04-28 op     <[-]                     Clear remainder from first division if second division was skipped
26 6572a112 2022-04-28 op     <.[-]                    Output ROT13ed character from copy and clear it
27 6572a112 2022-04-28 op     <-,+                     Read next character
28 6572a112 2022-04-28 op ]                            End character reading loop