From 9e4dffef2b7895d8e346294eaef1b38dcdfeec91 Mon Sep 17 00:00:00 2001
From: Pekka Laiho <pekka.i.laiho@gmail.com>
Date: Mon, 1 Jun 2020 20:19:26 +0700
Subject: [PATCH] support for (doc)

---
 src/CoreFunc.php |  5 ++---
 src/Func.php     |  9 ++++++++-
 src/Lisp.php     | 10 ++++++++++
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/src/CoreFunc.php b/src/CoreFunc.php
index 9a98538..d5f2acc 100644
--- a/src/CoreFunc.php
+++ b/src/CoreFunc.php
@@ -6,17 +6,16 @@ use Closure;
 class CoreFunc extends Func
 {
     protected string $name;
-    protected string $doc;
     protected int $minArgs;
     protected int $maxArgs;
 
     public function __construct(string $name, string $doc, int $minArgs, int $maxArgs, Closure $closure)
     {
+        parent::__construct($closure, $doc);
+
         $this->name = $name;
-        $this->doc = $doc;
         $this->minArgs = $minArgs;
         $this->maxArgs = $maxArgs;
-        $this->closure = $closure;
     }
 
     public function call(array $args)
diff --git a/src/Func.php b/src/Func.php
index 1f88580..21662ea 100644
--- a/src/Func.php
+++ b/src/Func.php
@@ -6,10 +6,12 @@ use Closure;
 abstract class Func
 {
     protected Closure $closure;
+    protected ?string $doc;
 
-    public function __construct(Closure $closure)
+    public function __construct(Closure $closure, ?string $doc = null)
     {
         $this->closure = $closure;
+        $this->doc = $doc;
     }
 
     public function getClosure(): Closure
@@ -17,6 +19,11 @@ abstract class Func
         return $this->closure;
     }
 
+    public function getDoc(): ?string
+    {
+        return $this->doc;
+    }
+
     public function call(array $args)
     {
         return ($this->closure)(...$args);
diff --git a/src/Lisp.php b/src/Lisp.php
index 9fdb9fc..05cde8d 100644
--- a/src/Lisp.php
+++ b/src/Lisp.php
@@ -29,6 +29,16 @@ class Lisp
 
     public function register(Env $env): void
     {
+        $env->set('doc', new CoreFunc('doc', 'Get documentation for a function.', 1, 1,
+            function ($a) {
+                if ($a instanceof Func) {
+                    return $a->getDoc();
+                }
+
+                throw new MadLispException('first argument to doc is not function');
+            }
+        ));
+
         $env->set('eval', new CoreFunc('eval', 'Evaluate arguments.', 1, -1,
             function (...$args) use ($env) {
                 $results = $this->eval->eval($args, $env);