diff --git a/src/aeso_ast_to_fcode.erl b/src/aeso_ast_to_fcode.erl
index b3363fd..5a46718 100644
--- a/src/aeso_ast_to_fcode.erl
+++ b/src/aeso_ast_to_fcode.erl
@@ -448,8 +448,8 @@ expr_to_fcode(Env, _Type, {list_comp, _, Yield, []}) ->
 expr_to_fcode(Env, _Type, {list_comp, As, Yield, [{comprehension_bind, {typed, {id, _, Arg}, _}, BindExpr}|Rest]}) ->
     Env1 = bind_var(Env, Arg),
     Bind = {lam, [Arg], expr_to_fcode(Env1, {list_comp, As, Yield, Rest})},
-    {funcall, resolve_fun(Env, ["List", "flat_map"]), [expr_to_fcode(Env, BindExpr), Bind]};
-
+    {def_u, FlatMap, _} = resolve_fun(Env, ["List", "flat_map"]),
+    {def, FlatMap, [Bind, expr_to_fcode(Env, BindExpr)]};
 
 %% Conditionals
 expr_to_fcode(Env, _Type, {'if', _, Cond, Then, Else}) ->
diff --git a/src/aeso_parser.erl b/src/aeso_parser.erl
index 25fc23a..de71794 100644
--- a/src/aeso_parser.erl
+++ b/src/aeso_parser.erl
@@ -505,7 +505,7 @@ parse_pattern(E = {bool, _, _})   -> E;
 parse_pattern(E = {bytes, _, _})  -> E;
 parse_pattern(E = {string, _, _}) -> E;
 parse_pattern(E = {char, _, _})   -> E;
-parse_pattern(E) -> bad_expr_err("Not a valid pattern", E).
+parse_pattern(E) -> bad_expr_err("Not a valid patxstern", E).
 
 -spec parse_field_pattern(aeso_syntax:field(aeso_syntax:expr())) -> aeso_parse_lib:parser(aeso_syntax:field(aeso_syntax:pat())).
 parse_field_pattern({field, Ann, F, E}) ->
@@ -532,8 +532,10 @@ expand_includes(AST, Opts) ->
 
 expand_includes([], Acc, _Opts) ->
     {ok, lists:reverse(Acc)};
-expand_includes([{include, _, S = {string, _, File}} | AST], Acc, Opts) ->
+expand_includes([{include, Ann, S = {string, _, File}} | AST], Acc, Opts) ->
     case {read_file(File, Opts), maps:find(File, aeso_stdlib:stdlib())} of
+        {{ok, _}, {ok,_ }} ->
+            return_error(ann_pos(Ann), "Illegal redefinition of standard library " ++ File);
         {_, {ok, Lib}} ->
             case string(Lib) of
                 {ok, AST1} ->
diff --git a/src/aeso_stdlib.erl b/src/aeso_stdlib.erl
index 4cbc768..8ac8351 100644
--- a/src/aeso_stdlib.erl
+++ b/src/aeso_stdlib.erl
@@ -21,10 +21,15 @@ stdlib() ->
 std_list() ->
 "
 namespace List =
+
+  function empty(l) = switch(l)
+    [] => true
+    _  => false
+
   function length(l) = length_(l, 0)
-  private function length_(l, n) = switch(l)
-    [] => n
-    _::t => length_(t, n + 1)
+  private function length_(l, acc) = switch(l)
+    [] => acc
+    _::t => length_(t, acc + 1)
 
   function foldr(cons, nil, l) = switch(l)
     [] => nil
@@ -34,8 +39,7 @@ namespace List =
     [] => acc
     h::t => foldl(rcons, rcons(acc, h), t)
 
-  function reverse(l) =
-    foldr((el, cont) => (lst) => cont(el::lst), (x) => x, l)([])
+  function reverse(l) = foldl((lst, el) => el :: lst, [], l)
 
   function map(f, l) = map_(f, l, [])
   private function map_(f, l, acc) = switch(l)
@@ -45,4 +49,62 @@ namespace List =
   function flat_map(f, l) = switch(l)
     [] => []
     h::t => f(h) ++ flat_map(f, t)
+
+  function concats(ll) = foldr((l1, l2) => l1 ++ l2, [], ll)
+
+  function filter(p, l) = filter_(p, l, [])
+  private function filter_(p, l, acc) = switch(l)
+    [] => reverse(acc)
+    h::t => filter_(p, t, if(p(h)) h::acc else acc)
+
+  function all(p, l) = foldl((prev, next) => prev && p(next), true, l)
+  function any(p, l) = foldl((prev, next) => prev || p(next), false, l)
+
+  /* Take `n` first elements */
+  function take(n, l) = if(n < 0) abort(\"Take negative number of elements\") else take_(n, l, [])
+  private function take_(n, l, acc) =
+    if(n == 0) reverse(acc)
+    else switch(l)
+      [] => reverse(acc)
+      h::t => take_(n-1, t, h::acc)
+
+  /* Drop `n` first elements */
+  function drop(n, l) =
+   if(n < 0) abort(\"Drop negative number of elements\")
+   elif (n == 0) l
+   else switch(l)
+      [] => []
+      h::t => drop(n-1, t)
+
+  /* Get the longest prefix of a list in which every element matches predicate `p` */
+  function take_while(p, l) = take_while_(p, l, [])
+  private function take_while_(p, l, acc) = switch(l)
+    [] => reverse(acc)
+    h::t => if(p(h)) take_while_(p, t, h::acc) else reverse(acc)
+
+  /* Drop elements from `l` until `p` holds */
+  function drop_while(p, l) = switch(l)
+    [] => []
+    h::t => if(p(h)) drop_while(p, t) else l
+
+  /* Zips two list by applying bimapping function on respective elements. Drops longer tail. */
+  function zip_with(f, l1, l2) = zip_with_(f, l1, l2, [])
+  private function zip_with_(f, l1, l2, acc) = switch ((l1, l2))
+    (h1::t1, h2::t2) => zip_with_(f, t1, t2, f(h1, h2)::acc)
+    _ => reverse(acc)
+
+  /* Zips two lists into list of pairs. Drops longer tail. */
+  function zip(l1, l2) = zip_with((a, b) => (a, b), l1, l2)
+
+  /* Splits list into two lists of elements that respectively match and don't match predicate `p` */
+  function partition(p, l) = partition_(p, l, [], [])
+  private function partition_(p, l, acc_t, acc_f) = switch(l)
+    [] => (reverse(acc_t), reverse(acc_f))
+    h::t => if(p(h)) partition_(p, t, h::acc_t, acc_f) else partition_(p, t, acc_t, h::acc_f)
+
+  // TODO: Improve?
+  function sort(lesser_cmp, l) = switch(l)
+    [] => []
+    h::t => switch (partition((x) => lesser_cmp(x, h), t))
+      (lesser, bigger) => sort(lesser_cmp, lesser) ++ h::sort(lesser_cmp, bigger)
 ".