* Builtin functions `head' and `tail' to return the head and tail of

  list.  Useful for lots of things, such as implementing a fold
  function (see NIX-30, example is in tests/lang/eval-okay-list.nix).

1 files changed, 13 insertions, 0 deletions

diff --git a/tests/lang/eval-okay-list.nix b/tests/lang/eval-okay-list.nix
new file mode 100644
index 000000000000..72a120d0d0f2
--- /dev/null
+++ b/tests/lang/eval-okay-list.nix
@@ -0,0 +1,13 @@
+let {
+
+  fold = op: nul: list:
+    if list == []
+    then nul
+    else op (builtins.head list) (fold op nul (builtins.tail list));
+
+  concat =
+    fold (x: y: x + y) "";
+
+  body = concat ["foo" "bar" "bla" "test"];
+    
+}
\ No newline at end of file