From 809a39ffe11a45fc74951ad4e79eaacb63731f1c Mon Sep 17 00:00:00 2001
From: Nat Quayle Nelson <natquaylenelson@gmail.com>
Date: Sat, 5 Dec 2020 19:06:15 -0700
Subject: [PATCH] (zip [l1] [l2])

---
 src/kiss/Kiss.hx                  |  2 +-
 src/kiss/Prelude.hx               | 28 ++++++++++++++++++++++++++++
 src/test/cases/BasicTestCase.hx   |  7 +++++--
 src/test/cases/BasicTestCase.kiss | 17 +++++++++++++----
 4 files changed, 47 insertions(+), 7 deletions(-)

diff --git a/src/kiss/Kiss.hx b/src/kiss/Kiss.hx
index bd3c521..af712a1 100644
--- a/src/kiss/Kiss.hx
+++ b/src/kiss/Kiss.hx
@@ -50,7 +50,7 @@ class Kiss {
             // Helpful aliases
             k.defAlias("print", Symbol("Prelude.print"));
             k.defAlias("groups", Symbol("Prelude.groups"));
-
+            k.defAlias("zip", Symbol("Prelude.zip"));
             k.defAlias("map", Symbol("Lambda.map"));
             k.defAlias("filter", Symbol("Lambda.filter")); // TODO use truthy as the default filter function
             k.defAlias("has", Symbol("Lambda.has"));
diff --git a/src/kiss/Prelude.hx b/src/kiss/Prelude.hx
index 79c6c8b..9976a16 100644
--- a/src/kiss/Prelude.hx
+++ b/src/kiss/Prelude.hx
@@ -158,6 +158,34 @@ class Prelude {
         return fullGroups;
     }
 
+    public static function zip<A, B>(a:Array<A>, b:Array<B>, extraHandling = Drop):Array<Array<Dynamic>> {
+        var max = Math.floor(if (a.length != b.length) {
+            switch (extraHandling) {
+                case Throw:
+                    throw 'zip was given lists of mis-matched size: $a, $b';
+                case Keep:
+                    Math.max(a.length, b.length);
+                case Drop:
+                    Math.min(a.length, b.length);
+            }
+        } else {
+            a.length;
+        });
+
+        return [
+            for (idx in 0...max) [
+                if (idx < a.length)
+                    a[idx]
+                else
+                    null,
+                if (idx < b.length)
+                    b[idx]
+                else
+                    null
+            ]
+        ];
+    }
+
     public static dynamic function truthy(v:Any) {
         return switch (Type.typeof(v)) {
             case TNull: false;
diff --git a/src/test/cases/BasicTestCase.hx b/src/test/cases/BasicTestCase.hx
index 0e3d8f2..d76682b 100644
--- a/src/test/cases/BasicTestCase.hx
+++ b/src/test/cases/BasicTestCase.hx
@@ -136,8 +136,11 @@ class BasicTestCase extends Test {
     }
 
     function testGroups() {
-        Assert.equals([[1, 2], [3, 4]].toString(), BasicTestCase.myGroups1().toString());
-        Assert.equals([[1, 2, 3], [4]].toString(), BasicTestCase.myGroups2().toString());
+        _testGroups();
+    }
+
+    function testZip() {
+        _testZip();
     }
 
     function testLet() {
diff --git a/src/test/cases/BasicTestCase.kiss b/src/test/cases/BasicTestCase.kiss
index 4326d72..4683090 100644
--- a/src/test/cases/BasicTestCase.kiss
+++ b/src/test/cases/BasicTestCase.kiss
@@ -114,11 +114,20 @@
 (defun myTypeCheck []
     (the Int 5))
 
-(defun myGroups1 []
-    (groups [1 2 3 4] 2))
+(defun _testGroups []
+    (Assert.equals (.toString [[1 2] [3 4]]) (.toString (groups [1 2 3 4] 2)))
+    (Assert.equals (.toString [[1 2 3] [4]]) (.toString (groups [1 2 3 4] 3 Keep)))
+    (try (begin (groups [1 2 3 4] 3 Throw) (Assert.fail))
+        (catch [error] (Assert.pass))))
 
-(defun myGroups2 []
-    (groups [1 2 3 4] 3 Keep))
+(defun _testZip []
+    (Assert.equals (.toString [[1 2] [3 4]]) (.toString (zip [1 3] [2 4] Throw)))
+    (Assert.equals (.toString [[1 2] [3 null]]) (.toString (zip [1 3] [2] Keep)))
+    (Assert.equals (.toString [[1 2] [null 4]]) (.toString (zip [1 null] [2 4] Keep)))
+    (try (begin (zip [1 3] [2] Throw) (Assert.fail))
+        (catch [error] (Assert.pass)))
+    (try (begin (zip [1] [2 4] Throw) (Assert.fail))
+        (catch [error] (Assert.pass))))
 
 (defun _testLet []
     (let [a 5