unbits word in math.bits vocab

basis/math/bits/bits-docs.factor

@@ -1,6 +1,6 @@
 ! Copyright (C) 2009 Daniel Ehrenberg
 ! See http://factorcode.org/license.txt for BSD license.
-USING: help.syntax help.markup math ;
+USING: help.syntax help.markup math sequences ;
 IN: math.bits
 
 ABOUT: "math.bits"
@@ -24,3 +24,7 @@ HELP: make-bits
     { $example "USING: math.bits prettyprint arrays ;" "BIN: 1101 make-bits >array ." "{ t f t t }" }
     { $example "USING: math.bits prettyprint arrays ;" "-3 make-bits >array ." "{ t f }" }
 } ;
+
+HELP: unbits
+{ $values { "seq" sequence } { "number" integer } }
+{ $description "Turns a sequence of booleans, of the same format made by the " { $link bits } " class, and calculates the number that it represents as little-endian." } ;

basis/math/bits/bits-tests.factor

@@ -29,3 +29,6 @@ IN: math.bits.tests
 [ t ] [
     1067811677921310779 >bignum make-bits last
 ] unit-test
+
+[ 6 ] [ 6 make-bits unbits ] unit-test
+[ 6 ] [ 6 3 <bits> >array unbits ] unit-test

basis/math/bits/bits.factor

@@ -14,3 +14,6 @@ M: bits length length>> ;
 M: bits nth-unsafe number>> swap bit? ;
 
 INSTANCE: bits immutable-sequence
+
+: unbits ( seq -- number )
+    <reversed> 0 [ [ 1 shift ] dip [ 1+ ] when ] reduce ;