diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index c734050..b3ce7d1 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -60,6 +60,9 @@ functionaltest("map")
 functionaltest("deconstruct")
 functionaltest("shadowing")
 functionaltest("mathops")
+functionaltest("len")
+functionaltest("not")
+functionaltest("type")
 
 install(TARGETS apfl DESTINATION lib)
 install(TARGETS apfl-bin DESTINATION bin)
diff --git a/src/functional-tests/len.at b/src/functional-tests/len.at
new file mode 100644
index 0000000..070c54a
--- /dev/null
+++ b/src/functional-tests/len.at
@@ -0,0 +1,17 @@
+===== script =====
+print (len "")
+print (len "Hello")
+print (len [])
+print (len [1 2 3 4])
+print (len [[]])
+print (len [->])
+print (len ['a -> 'b, 'c-> 'd])
+
+===== output =====
+0
+5
+0
+4
+1
+0
+2
diff --git a/src/functional-tests/not.at b/src/functional-tests/not.at
new file mode 100644
index 0000000..d61850f
--- /dev/null
+++ b/src/functional-tests/not.at
@@ -0,0 +1,35 @@
+===== script =====
+print (not true)
+print (not false)
+print (not nil)
+print (not 0)
+print (not 1)
+print (not -1)
+print (not 42)
+print (not "")
+print (not "foo")
+print (not [])
+print (not [1])
+print (not [true])
+print (not [false])
+print (not [->])
+print (not ['x -> 'y])
+print (not {})
+
+===== output =====
+false
+true
+true
+false
+false
+false
+false
+false
+false
+false
+false
+false
+false
+false
+false
+false
diff --git a/src/functional-tests/type.at b/src/functional-tests/type.at
new file mode 100644
index 0000000..4fab599
--- /dev/null
+++ b/src/functional-tests/type.at
@@ -0,0 +1,21 @@
+===== script =====
+print (type true)
+print (type false)
+print (type nil)
+print (type "test")
+print (type [])
+print (type ["test"])
+print (type [1->2])
+print (type {x->x})
+print (type type)
+
+===== output =====
+bool
+bool
+nil
+string
+list
+list
+dict
+function
+function
diff --git a/src/globals.c b/src/globals.c
index 55172ff..c977162 100644
--- a/src/globals.c
+++ b/src/globals.c
@@ -206,18 +206,74 @@ disasm(apfl_ctx ctx)
 }
 
 static void
-tostring(apfl_ctx ctx)
+require_exactly_one_arg(apfl_ctx ctx, const char *error)
 {
     size_t len = apfl_len(ctx, 0);
     if (len != 1) {
-        apfl_raise_const_error(ctx, APFL_RESULT_ERR, "tostring needs exactly 1 argument");
+        apfl_raise_const_error(ctx, APFL_RESULT_ERR, error);
     }
 
     apfl_get_list_member_by_index(ctx, 0, 0);
     apfl_drop(ctx, 0);
+}
+
+#define ONE_ARG(ctx, name) require_exactly_one_arg((ctx), name " needs exactly 1 argument")
+
+static void
+tostring(apfl_ctx ctx)
+{
+    ONE_ARG(ctx, "tostring");
     apfl_tostring(ctx, -1);
 }
 
+static void
+not(apfl_ctx ctx)
+{
+    ONE_ARG(ctx, "not");
+    bool b = apfl_is_truthy(ctx, -1);
+    apfl_push_bool(ctx, !b);
+}
+
+static void
+len(apfl_ctx ctx)
+{
+    ONE_ARG(ctx, "len");
+    size_t l = apfl_len(ctx, -1);
+    apfl_push_number(ctx, (apfl_number)l);
+}
+
+static const char *
+typestr(enum apfl_value_type type)
+{
+    switch (type) {
+    case APFL_VALUE_NIL:
+        return "nil";
+    case APFL_VALUE_BOOLEAN:
+        return "bool";
+    case APFL_VALUE_NUMBER:
+        return "number";
+    case APFL_VALUE_STRING:
+        return "string";
+    case APFL_VALUE_LIST:
+        return "list";
+    case APFL_VALUE_DICT:
+        return "dict";
+    case APFL_VALUE_FUNC:
+        return "function";
+    case APFL_VALUE_USERDATA:
+        return "userdata";
+    }
+
+    return "?";
+}
+
+static void
+type(apfl_ctx ctx)
+{
+    ONE_ARG(ctx, "type");
+    apfl_push_const_string(ctx, typestr(apfl_get_type(ctx, -1)));
+}
+
 static const struct global_def globals[] = {
     {"if", impl_if},
     {"==", impl_eq},
@@ -229,6 +285,9 @@ static const struct global_def globals[] = {
     {"dump", dump},
     {"disasm", disasm},
     {"tostring", tostring},
+    {"not", not},
+    {"len", len},
+    {"type", type},
     {NULL, NULL},
 };