put a random method on intervals, works for float and integer intervals

basis/math/intervals/intervals.factor

@@ -1,8 +1,9 @@
-! Copyright (C) 2007, 2008 Slava Pestov.
+! Copyright (C) 2007, 2008 Slava Pestov, Doug Coleman.
 ! See http://factorcode.org/license.txt for BSD license.
 ! Based on Slate's src/unfinished/interval.slate by Brian Rice.
 USING: accessors kernel sequences arrays math math.order
-combinators generic ;
+combinators generic random math.constants qualified ;
+FROM: math.ranges => <range> ;
 IN: math.intervals
 
 SYMBOL: empty-interval
@@ -396,3 +397,37 @@ SYMBOL: incomparable
         [ to>> first2 [ 1- ] unless ]
         bi [a,b]
     ] unless ;
+
+<PRIVATE
+
+: open-left? ( interval -- ? ) from>> second not ;
+
+: open-right? ( interval -- ? ) to>> second not ;
+
+: integral-interval? ( interval -- ? )
+    [ from>> ] [ to>> ] bi [ first integer? ] both? ;
+
+PRIVATE>
+
+ERROR: empty-random-interval ;
+
+: random-interval-integer ( interval -- n )
+    [ [ to>> first ] [ open-right? [ 1- ] when ] bi ]
+    [
+        [ from>> first ]
+        [ open-left? [ 1+ ] when ] bi
+        tuck - 1+ random +
+    ] bi ;
+
+: random-interval-float ( interval -- x )
+    [ [ from>> first ] [ open-left? [ epsilon + ] when ] bi ]
+    [ [ to>> first ] [ open-right? [ epsilon - ] when ] bi ] bi
+    epsilon <range> random [ empty-random-interval ] unless* ;
+
+M: interval random ( interval -- x )
+    dup empty-interval = [ empty-random-interval ] when
+    dup integral-interval? [
+        random-interval-integer
+    ] [
+        random-interval-float
+    ] if ;