From 6debf1e39ab902eeabf4ca806ef1168a5185ffe7 Mon Sep 17 00:00:00 2001
From: Natalie Weizenbaum <nex342@gmail.com>
Date: Thu, 22 Sep 2016 09:40:22 -0700
Subject: [PATCH] Add zip().

---
 lib/src/functions.dart       | 15 +++++++++++++++
 lib/src/visitor/perform.dart |  9 ++++++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/lib/src/functions.dart b/lib/src/functions.dart
index 076f1341..33b4d140 100644
--- a/lib/src/functions.dart
+++ b/lib/src/functions.dart
@@ -588,6 +588,21 @@ void defineCoreFunctions(Environment environment) {
     return list.changeListContents(newList, separator: separator);
   });
 
+  environment.defineFunction("zip", r"$lists...", (arguments) {
+    var lists = (arguments[0] as SassArgumentList)
+        .contents
+        .map((list) => list.asList)
+        .toList();
+    var i = 0;
+    var results = <SassList>[];
+    while (lists.every((list) => i != list.length)) {
+      results
+          .add(new SassList(lists.map((list) => list[i]), ListSeparator.space));
+      i++;
+    }
+    return new SassList(results, ListSeparator.comma);
+  });
+
   // ## Introspection
 
   environment.defineFunction("inspect", r"$value",
diff --git a/lib/src/visitor/perform.dart b/lib/src/visitor/perform.dart
index f4535260..22d6b547 100644
--- a/lib/src/visitor/perform.dart
+++ b/lib/src/visitor/perform.dart
@@ -795,9 +795,12 @@ class PerformVisitor implements StatementVisitor, ExpressionVisitor<Value> {
 
     SassArgumentList argumentList;
     if (overload.restArgument != null) {
-      var rest = positional.length > declaredArguments.length
-          ? positional.sublist(declaredArguments.length)
-          : const <Value>[];
+      var rest = const <Value>[];
+      if (positional.length > declaredArguments.length) {
+        rest = positional.sublist(declaredArguments.length);
+        positional.removeRange(declaredArguments.length, positional.length);
+      }
+
       argumentList = new SassArgumentList(
           rest,
           named,