drop-while, fixes #54

core.js

@@ -824,10 +824,28 @@ export function cycle(coll) {
 
 export function drop(n, xs) {
   return new LazyIterable(function* () {
-    let iter = _iterator(xs);
+    let iter = _iterator(iterable(xs));
     for (let x = 0; x < n; x++) {
       iter.next();
     }
     yield* iter;
   });
 }
+
+export function drop_while(pred, xs) {
+  return new LazyIterable(function* () {
+    let iter = _iterator(iterable(xs));
+    while (true) {
+      let nextItem = iter.next();
+      if (nextItem.done) {
+        break;
+      }
+      let value = nextItem.value;
+      if (!pred(value)) {
+        yield value;
+        break;
+      }
+    }
+    yield* iter;
+  });
+}

resources/clava/core.edn

@@ -27,6 +27,7 @@
   dissoc
   dissoc_BANG_
   drop
+  drop_while
   empty
   es6_iterator
   even_QMARK_

test/clava/compiler_test.cljs

@@ -1023,7 +1023,15 @@
   (let [dropped (jsv! '(drop 3 (range 6)))]
     (is (eq [3 4 5] (vec dropped)))
     ;; iterating over dropped second time, still works:
-    (is (eq [3 4 5] (vec dropped)))))
+    (is (eq [3 4 5] (vec dropped))))
+  (is (eq (drop 2 nil) (vec (jsv! '(drop 2 nil))))))
+
+(deftest drop-while-test
+  (let [dropped (jsv! '(drop-while odd? [1 1 1 2 3 4]))]
+    (is (eq (drop-while odd? [1 1 1 2 3 4]) (vec dropped)))
+    ;; iterating over dropped second time, still works:
+    (is (eq (drop-while odd? [1 1 1 2 3 4]) (vec dropped))))
+  (is (eq (drop-while odd? nil) (vec (jsv! '(drop-while odd? nil))))))
 
 (defn init []
   (cljs.test/run-tests 'clava.compiler-test 'clava.jsx-test))