lazy-lists: add lazy reading of characters from a file

contrib/lazy-lists/lazy-io.factor

@@ -0,0 +1,34 @@
+! Copyright (C) 2006 Chris Double.
+! See http://factorcode.org/license.txt for BSD license.
+
+USING: kernel lazy-lists io ;
+IN: lazy-lists
+
+TUPLE: lazy-contents stream car cdr ;
+
+: lcontents ( stream -- result )
+  f f <lazy-contents> ;
+
+M: lazy-contents car ( lazy-contents -- car )
+  dup lazy-contents-car dup [
+    nip  
+  ] [ 
+    drop dup lazy-contents-stream stream-read1 
+    swap dupd set-lazy-contents-car
+  ] if ;
+
+M: lazy-contents cdr ( lazy-contents -- cdr )
+  dup lazy-contents-cdr dup [
+    nip
+  ] [
+    drop dup
+    [ lazy-contents-stream ] keep
+    car [
+      lcontents [ swap set-lazy-contents-cdr ] keep
+    ] [
+      2drop nil
+    ] if 
+  ] if ;
+
+M: lazy-contents nil? ( lazy-contents -- bool )
+  car not ;

contrib/lazy-lists/lazy-io.facts

@@ -0,0 +1,10 @@
+! Copyright (C) 2006 Chris Double.
+! See http://factorcode.org/license.txt for BSD license.
+
+USING: help lazy-lists sequences ;
+
+HELP: lcontents
+{ $values { "stream" "a stream" } }
+{ $description "Returns a lazy list of all characters in the file. " { $link car } " returns the next character in the file, " { $link cdr } " returns the remaining characters as a lazy list. " { $link nil? } " indicates end of file." } 
+{ $see-also leach lmap ltake lsubset lfrom lfrom-by } ;
+

contrib/lazy-lists/load.factor

@@ -4,6 +4,8 @@
 PROVIDE: contrib/lazy-lists { 
     "lists.factor"
     "lists.facts"
+    "lazy-io.factor"
+    "lazy-io.facts"
     "examples.factor"
 } {
     "test/lists.factor"