Added Makefile

1 files changed, 28 insertions, 0 deletions

diff --git a/examples/rot13.bf b/examples/rot13.bf
new file mode 100644
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+++ b/examples/rot13.bf
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+-,+[                          ; 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