From 0a78720644e45bd27c4a57cbddf2d32aacb555c3 Mon Sep 17 00:00:00 2001
From: Case Duckworth
Date: Wed, 29 Jun 2022 00:59:59 -0500
Subject: Probably version ... whatever the next higher one is

---
 examples/rot13.bf | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 examples/rot13.bf

(limited to 'examples/rot13.bf')

diff --git a/examples/rot13.bf b/examples/rot13.bf
new file mode 100644
index 0000000..bfcde73
--- /dev/null
+++ b/examples/rot13.bf
@@ -0,0 +1,32 @@
+[ ROT13 in Brainfuck
+from https://en.wikipedia.org/wiki/Brainfuck#ROT13
+]
+
+-,+[                         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
-- 
cgit 1.4.1-21-gabe81