1 files changed, 77 insertions, 0 deletions
diff --git a/src/lib/list.rs b/src/lib/list.rs
new file mode 100644
index 00000000..86d6c21d
--- /dev/null
+++ b/src/lib/list.rs
@@ -0,0 +1,77 @@
+import option::some;
+import option::none;
+
+// FIXME: It would probably be more appealing to define this as
+// type list[T] = rec(T hd, option[@list[T]] tl), but at the moment
+// our recursion rules do not permit that.
+
+tag list[T] {
+    cons(T, @list[T]);
+    nil;
+}
+
+fn foldl[T,U](&list[T] ls, &U u, fn(&T t, &U u) -> U f) -> U {
+  alt(ls) {
+    case (cons[T](?hd, ?tl)) {
+      auto u_ = f(hd, u);
+      // FIXME: should use 'be' here, not 'ret'. But parametric
+      // tail calls currently don't work.
+      ret foldl[T,U](*tl, u_, f);
+    }
+    case (nil[T]) {
+      ret u;
+    }
+  }
+
+  fail; // TODO: remove me when exhaustiveness checking works
+}
+
+fn find[T,U](&list[T] ls,
+             (fn(&T) -> option::t[U]) f) -> option::t[U] {
+  alt(ls) {
+    case (cons[T](?hd, ?tl)) {
+        alt (f(hd)) {
+            case (none[U]) {
+                // FIXME: should use 'be' here, not 'ret'. But parametric tail
+                // calls currently don't work.
+                ret find[T,U](*tl, f);
+            }
+            case (some[U](?res)) {
+                ret some[U](res);
+            }
+        }
+    }
+    case (nil[T]) {
+        ret none[U];
+    }
+  }
+
+  fail; // TODO: remove me when exhaustiveness checking works
+}
+
+fn length[T](&list[T] ls) -> uint {
+  fn count[T](&T t, &uint u) -> uint {
+    ret u + 1u;
+  }
+  ret foldl[T,uint](ls, 0u, bind count[T](_, _));
+}
+
+fn cdr[T](&list[T] ls) -> list[T] {
+    alt (ls) {
+        case (cons[T](_, ?tl)) {ret *tl;}
+    }
+}
+fn car[T](&list[T] ls) -> T {
+    alt (ls) {
+        case (cons[T](?hd, _)) {ret hd;}
+    }
+}
+
+// Local Variables:
+// mode: rust;
+// fill-column: 78;
+// indent-tabs-mode: nil
+// c-basic-offset: 4
+// buffer-file-coding-system: utf-8-unix
+// compile-command: "make -k -C .. 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
+// End: