2016-04-06: safepassword: provide 3 implementations

safepassword: provide 3 implementations

diff --git a/examples/safepassword.w b/examples/safepassword.w
--- a/examples/safepassword.w
+++ b/examples/safepassword.w
@@ -11,22 +11,73 @@ define-module : examples safepassword
 import
     only (srfi srfi-27) random-source-make-integers
       . make-random-source random-source-randomize!
-    only (srfi srfi-1) second
+    only (srfi srfi-1) second third iota
+    srfi srfi-42
+
 
 define random-source : make-random-source
 random-source-randomize! random-source
 
+
 define random-integer 
        random-source-make-integers random-source
 
+
 define : randomletter letters
       string-ref letters
         random-integer
           string-length letters
 
+
+define : flatten e
+    cond 
+       : pair? e
+         ` ,@(flatten (car e)) ,@(flatten (cdr e))
+       : null? e
+         list
+       else 
+         list e
+
+
+define : password/srfi-42 length
+      let
+       : qwertysafeletters "0123456789ABCDEFGHJKLMNPQRSTUVWXabcdefghijkmnopqrstuvwx"
+         ;; that’s newbase60 without yz_
+         ;; means 5.78 bits of entropy per letter.
+         delimiters ",.!?-"
+         ;; that’s 2.32 bits of entropy per delimiter
+       list->string
+         append-ec (: i (iota length 1))
+           cons : randomletter qwertysafeletters
+             if : and (not (= i length)) : zero? : modulo i 4
+                cons : randomletter delimiters
+                  list
+                list
+
+
+define : password/map length
+      let
+       : qwertysafeletters "0123456789ABCDEFGHJKLMNPQRSTUVWXabcdefghijkmnopqrstuvwx"
+         ;; that’s newbase60 without yz_
+         ;; means 5.78 bits of entropy per letter.
+         delimiters ",.!?-"
+         ;; that’s 2.32 bits of entropy per delimiter
+       list->string
+         flatten
+           map
+             lambda : i
+               let
+                 : letter : randomletter qwertysafeletters
+                 if : and (not (= i length)) : zero? : modulo i 4
+                    list letter 
+                      randomletter delimiters
+                    list letter
+             iota length 1
+
+
 define : password length
       let
-       : quertysafeletters "0123456789ABCDEFGHJKLMNPQRSTUVWXabcdefghijkmnopqrstuvwx"
+       : qwertysafeletters "0123456789ABCDEFGHJKLMNPQRSTUVWXabcdefghijkmnopqrstuvwx"
          ;; that’s newbase60 without yz_
          ;; means 5.78 bits of entropy per letter.
          delimiters ",.!?-"
@@ -37,19 +88,28 @@ define : password length
          if : zero? remaining
             reverse-list->string letters
             fill
-              cons : randomletter quertysafeletters
+              cons : randomletter qwertysafeletters
                 if : and (not (= length remaining)) : zero? : modulo remaining 4
                    cons : randomletter delimiters
                         . letters
                    . letters
               - remaining 1
 
+
 define : main args
       let
        :
          len
-           if : = 2 : length args
+           if : <= 2 : length args
               string->number : second args
               . 16
-       display : password len
-       newline
+       let 
+         : idx (if (> 3 (length args)) 1 (string->number (third args)))
+         cond
+           : = idx 1
+             display : password len
+           : = idx 2
+             display : password/map len
+           : = idx 3
+             display : password/srfi-42 len
+         newline