From 550af52a65ec0760127ab7381d3bd9011600ad4f Mon Sep 17 00:00:00 2001
From: Nat Quayle Nelson <natquaylenelson@gmail.com>
Date: Mon, 30 Nov 2020 13:53:08 -0700
Subject: [PATCH] optional arguments

---
 src/kiss/Helpers.hx               | 47 ++++++++++++++++++-------------
 src/test/cases/BasicTestCase.hx   |  4 +++
 src/test/cases/BasicTestCase.kiss |  7 ++++-
 3 files changed, 38 insertions(+), 20 deletions(-)

diff --git a/src/kiss/Helpers.hx b/src/kiss/Helpers.hx
index 5a44234a..d767479e 100644
--- a/src/kiss/Helpers.hx
+++ b/src/kiss/Helpers.hx
@@ -55,8 +55,34 @@ class Helpers {
     }
 
     // TODO generic type parameter declarations
-
     public static function makeFunction(?name:ReaderExp, argList:ReaderExp, body:Array<ReaderExp>, k:KissState):Function {
+        // Once the &opt meta appears, all following arguments are optional until &rest
+        var opt = false;
+        // TODO rest arguments
+        // ^ rest arguments will have to define a macro with the function's name that wraps the rest args in a list when calling it from Kiss
+        function makeFuncArg(funcArg:ReaderExp):FunctionArg {
+            return switch (funcArg.def) {
+                case MetaExp("opt", innerFuncArg):
+                    opt = true;
+                    makeFuncArg(innerFuncArg);
+                default:
+                    {
+                        name: switch (funcArg.def) {
+                            case Symbol(name) | TypedExp(_, {pos: _, def: Symbol(name)}):
+                                name;
+                            default:
+                                throw CompileError.fromExp(funcArg, 'function argument should be a symbol or typed symbol');
+                        },
+                        type: switch (funcArg.def) {
+                            case TypedExp(type, _):
+                                Helpers.parseComplexType(type, funcArg);
+                            default: null;
+                        },
+                        opt: opt
+                    };
+            };
+        }
+
         return {
             ret: if (name != null) switch (name.def) {
                 case TypedExp(type, _): Helpers.parseComplexType(type, name);
@@ -64,24 +90,7 @@ class Helpers {
             } else null,
             args: switch (argList.def) {
                 case ListExp(funcArgs):
-                    [
-                        // TODO optional arguments, rest arguments
-                        // ^ rest arguments will have to define a macro with the function's name that wraps the rest args in a list when calling it from Kiss
-                        for (funcArg in funcArgs)
-                            {
-                                name: switch (funcArg.def) {
-                                    case Symbol(name) | TypedExp(_, {pos: _, def: Symbol(name)}):
-                                        name;
-                                    default:
-                                        throw CompileError.fromExp(funcArg, 'function argument should be a symbol or typed symbol');
-                                },
-                                type: switch (funcArg.def) {
-                                    case TypedExp(type, _):
-                                        Helpers.parseComplexType(type, funcArg);
-                                    default: null;
-                                }
-                            }
-                    ];
+                    funcArgs.map(makeFuncArg);
                 case CallExp(_, _):
                     throw CompileError.fromExp(argList, 'expected an argument list. Change the parens () to brackets []');
                 default:
diff --git a/src/test/cases/BasicTestCase.hx b/src/test/cases/BasicTestCase.hx
index 0129f916..59b69420 100644
--- a/src/test/cases/BasicTestCase.hx
+++ b/src/test/cases/BasicTestCase.hx
@@ -206,4 +206,8 @@ class BasicTestCase extends Test {
     function testDoFor() {
         _testDoFor();
     }
+
+    function testOptionalArguments() {
+        myOptionalFunc(5);
+    }
 }
diff --git a/src/test/cases/BasicTestCase.kiss b/src/test/cases/BasicTestCase.kiss
index eb0f8d08..93be921e 100644
--- a/src/test/cases/BasicTestCase.kiss
+++ b/src/test/cases/BasicTestCase.kiss
@@ -231,4 +231,9 @@
     (doFor [a e i] smallerMetaList
         (Assert.equals 1 a)
         (Assert.equals 5 e)
-        (Assert.equals 10 i)))
\ No newline at end of file
+        (Assert.equals 10 i)))
+
+    (defun myOptionalFunc [a &opt b c]
+        (Assert.equals 5 a)
+        (Assert.equals null b)
+        (Assert.equals 6 (or c 6))) // (or [optionalVar] [defaultValue]) is the convention for default values
\ No newline at end of file