Add Rot13 in Tcl (#5080)

Author: pascalecu

archive/t/tcl/rot13.tcl

@@ -0,0 +1,26 @@
+
+proc usage {} {
+    puts "Usage: please provide a string to encrypt"
+    exit 1
+}
+
+if {$argc != 1} { usage }
+set input [lindex $argv 0]
+if {$input eq ""} { usage }
+
+proc rot13 {text} {
+    set upper "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+    set lower "abcdefghijklmnopqrstuvwxyz"
+
+    set map {}
+
+    for {set i 0} {$i < 26} {incr i} {
+        lappend map [string index $upper $i] [string index $upper [expr {($i+13)%26}]]
+        lappend map [string index $lower $i] [string index $lower [expr {($i+13)%26}]]
+    }
+
+    return [string map $map $text]
+}
+
+puts [rot13 $input]
+