diff --git a/priv/stdlib/List.aes b/priv/stdlib/List.aes
index cdd2464..637faeb 100644
--- a/priv/stdlib/List.aes
+++ b/priv/stdlib/List.aes
@@ -37,14 +37,16 @@ namespace List =
     []   => reverse(acc)
     h::t => find_indices_(p, t, n+1, if(p(h)) n::acc else acc)
 
-  function nth(n : int, l : list('a)) : option('a) = switch(l)
-    []   => None
-    h::t => if(n == 0) Some(h) else nth(n-1, t)
+  function nth(n : int, l : list('a)) : option('a) =
+    if(n < 0) None else switch(l)
+      []   => None
+      h::t => if(n == 0) Some(h) else nth(n-1, t)
 
   /* Unsafe version of `nth` */
-  function get(n : int, l : list('a)) : 'a = switch(l)
-    [] => abort("Out of index get")
-    h::t => if(n == 0) h else get(n-1, t)
+  function get(n : int, l : list('a)) : 'a =
+    if(n < 0) abort("Negative index get") else switch(l)
+      [] => abort("Out of index get")
+      h::t => if(n == 0) h else get(n-1, t)
 
 
   function length(l : list('a)) : int = length_(l, 0)
@@ -53,6 +55,15 @@ namespace List =
     _::t => length_(t, acc + 1)
 
 
+  function from_to(a : int, b : int) : list(int) = from_to_(a, b, [])
+  private function from_to_(a, b, acc) =
+    if (a > b) acc else from_to_(a, b - 1, b :: acc)
+
+  function from_to_step(a : int, b : int, s : int) : list(int) = from_to_step_(a, b, s, [])
+  private function from_to_step_(a, b, s, acc) =
+    if (a > b) reverse(acc) else from_to_step_(a + s, b, s, a :: acc)
+
+
   /* Unsafe. Replaces `n`th element of `l` with `e`. Crashes on over/underflow */
   function replace_at(n : int, e : 'a, l : list('a)) : list('a) =
     if(n<0) abort("insert_at underflow") else replace_at_(n, e, l, [])
@@ -71,14 +82,17 @@ namespace List =
      []   => abort("insert_at overflow")
      h::t => insert_at_(n-1, e, t, h::acc)
 
-  function insert_by(f : (('a, 'a) => bool), x : 'a, l : list('a)) : list('a) =
+  function insert_by(cmp : (('a, 'a) => bool), x : 'a, l : list('a)) : list('a) =
+    insert_by_(cmp, x, l, [])
+  private function insert_by_(cmp : (('a, 'a) => bool), x : 'a, l : list('a), acc : list('a)) : list('a) =
     switch(l)
-      []        => [x]
-      (e :: l') =>
-        if(f(x, e))
-          e :: insert_by(f, x, l')
+      []   => reverse(x::acc)
+      h::t =>
+        if(cmp(x, e)) // x < e
+          reverse(acc) ++ (x::l)
         else
-          x :: l
+          insert_by(cmp, x, t, e::acc)
+
 
   function foldr(cons : ('a, 'b) => 'b, nil : 'b, l : list('a)) : 'b = switch(l)
     []   => nil
@@ -88,12 +102,12 @@ namespace List =
     []   => acc
     h::t => foldl(rcons, rcons(acc, h), t)
 
-  function foreach(f : 'a => unit, l : list('a)) : unit =
+  function foreach(l : list('a), f : 'a => unit) : unit =
     switch(l)
-     []   => ()
-     e :: l' =>
+     []    => ()
+     e::l' =>
        f(e)
-       foreach(f, l')
+       foreach(l', f)
 
   function reverse(l : list('a)) : list('a) = foldl((lst, el) => el :: lst, [], l)
 
@@ -149,7 +163,7 @@ namespace List =
     h::t => if(p(h)) partition_(p, t, h::acc_t, acc_f) else partition_(p, t, acc_t, h::acc_f)
 
 
-  function concats(ll : list(list('a))) : list('a) = foldr((l1, l2) => l1 ++ l2, [], ll)
+  function flatten(ll : list(list('a))) : list('a) = foldr((l1, l2) => l1 ++ l2, [], ll)
 
   function all(p : 'a => bool, l : list('a)) : bool = switch(l)
     []   => true
diff --git a/priv/stdlib/Option.aes b/priv/stdlib/Option.aes
index 843e62d..6ebf98c 100644
--- a/priv/stdlib/Option.aes
+++ b/priv/stdlib/Option.aes
@@ -19,7 +19,7 @@ namespace Option =
 
   function force(o : option('a)) : 'a = default(abort("Forced None value"), o)
 
-  function on_elem(f : 'a => unit, o : option('a)) : unit = match((), f, o)
+  function on_elem(o : option('a), f : 'a => unit) : unit = match((), f, o)
 
   function map(f : 'a => 'b, o : option('a)) : option('b) = switch(o)
     None => None