Merge branch 'lima' into master

priv/stdlib/List.aes

@@ -15,8 +15,8 @@ namespace List =
     _::t => Some(t)
 
   function last(l : list('a)) : option('a) = switch(l)
-    []  => None
-    [x] => Some(x)
+    []   => None
+    [x]  => Some(x)
     _::t => last(t)
 
   function drop_last(l : list('a)) : option(list('a)) = switch(l)
@@ -28,6 +28,11 @@ namespace List =
     h::t => h::drop_last_unsafe(t)
     []   => abort("drop_last_unsafe: list empty")
 
+
+  function contains(e : 'a, l : list('a)) = switch(l)
+    []   => false
+    h::t => h == e || contains(e, t)
+
 /** Finds first element of `l` fulfilling predicate `p` as `Some` or `None`
  * if no such element exists.
  */

priv/stdlib/Option.aes

@@ -22,7 +22,11 @@ namespace Option =
 
 /** Assume it is `Some`
  */
-  function force(o : option('a)) : 'a = default(abort("Forced None value"), o)
+  function force(o : option('a)) : 'a = switch(o)
+    None    => abort("Forced None value")
+    Some(x) => x
+
+  function contains(e : 'a, o : option('a)) = o == Some(e)
 
   function on_elem(o : option('a), f : 'a => unit) : unit = match((), f, o)