From 609f14656a0d74bb6244cf2f326c6d563094172f Mon Sep 17 00:00:00 2001
From: Nat Quayle Nelson <natquaylenelson@gmail.com>
Date: Sat, 5 Dec 2020 18:46:24 -0700
Subject: [PATCH] Improve (groups)

---
 src/kiss/Kiss.hx                  |  2 ++
 src/kiss/Prelude.hx               | 20 +++++++++++++++++---
 src/test/cases/BasicTestCase.kiss |  4 ++--
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/src/kiss/Kiss.hx b/src/kiss/Kiss.hx
index c06372f..bd3c521 100644
--- a/src/kiss/Kiss.hx
+++ b/src/kiss/Kiss.hx
@@ -49,6 +49,8 @@ class Kiss {
 
             // Helpful aliases
             k.defAlias("print", Symbol("Prelude.print"));
+            k.defAlias("groups", Symbol("Prelude.groups"));
+
             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 1f3f275..79c6c8b 100644
--- a/src/kiss/Prelude.hx
+++ b/src/kiss/Prelude.hx
@@ -5,6 +5,13 @@ using Std;
 import kiss.Operand;
 import haxe.ds.Either;
 
+/** What functions that process Lists should do when there are more elements than expected **/
+enum ExtraElementHandling {
+    Keep; // Keep the extra elements
+    Drop; // Drop the extra elements
+    Throw; // Throw an error
+}
+
 class Prelude {
     static function variadic(op:(Operand, Operand) -> Null<Operand>, comparison = false):(Array<Operand>) -> Dynamic {
         return (l:kiss.List<Operand>) -> switch (Lambda.fold(l.slice(1), op, l[0])) {
@@ -129,7 +136,7 @@ class Prelude {
 
     public static var areEqual = variadic(_areEqual, true);
 
-    public static function groups<T>(a:Array<T>, size, keepRemainder = false) {
+    public static function groups<T>(a:Array<T>, size, extraHandling = Drop) {
         var numFullGroups = Math.floor(a.length / size);
         var fullGroups = [
             for (num in 0...numFullGroups) {
@@ -138,9 +145,16 @@ class Prelude {
                 a.slice(start, end);
             }
         ];
-        if (a.length % size != 0 && keepRemainder) {
-            fullGroups.push(a.slice(numFullGroups * size));
+        if (a.length % size != 0) {
+            switch (extraHandling) {
+                case Throw:
+                    throw 'groups was given a non-divisible number of elements: $a, $size';
+                case Keep:
+                    fullGroups.push(a.slice(numFullGroups * size));
+                case Drop:
+            }
         }
+
         return fullGroups;
     }
 
diff --git a/src/test/cases/BasicTestCase.kiss b/src/test/cases/BasicTestCase.kiss
index 3aca019..4326d72 100644
--- a/src/test/cases/BasicTestCase.kiss
+++ b/src/test/cases/BasicTestCase.kiss
@@ -115,10 +115,10 @@
     (the Int 5))
 
 (defun myGroups1 []
-    (Prelude.groups [1 2 3 4] 2))
+    (groups [1 2 3 4] 2))
 
 (defun myGroups2 []
-    (Prelude.groups [1 2 3 4] 3 true))
+    (groups [1 2 3 4] 3 Keep))
 
 (defun _testLet []
     (let [a 5