From a38ef23e17dc3a9ac7aebd3b8b950e0dd0db4cde Mon Sep 17 00:00:00 2001
From: Pekka Laiho <pekka.i.laiho@gmail.com>
Date: Sun, 18 Oct 2020 10:24:18 +0700
Subject: [PATCH] add functions: loop, coinflip, rand

---
 README.md           |  3 +++
 src/Lib/Math.php    | 10 ++++++++++
 src/LispFactory.php |  9 +++++++++
 3 files changed, 22 insertions(+)

diff --git a/README.md b/README.md
index ce3318a..54eec2d 100644
--- a/README.md
+++ b/README.md
@@ -141,6 +141,7 @@ quote | `(quote (1 2 3))` | `(1 2 3)` | Return the argument without evaluation.
 Name  | Example | Example result | Description
 ----- | ------- | -------------- | -----------
 doc   | `(doc +)` | `"Return the sum of all arguments."` | Show description of a built-in function.
+loop  | `(loop (fn (a) (do (print a) (coinflip))) "hello ")` | `hello hello hello false` | Call the given function repeatedly in a loop until it returns false.
 read  | `(read "(+ 1 2 3)")` | `(+ 1 2 3)` | Read a string as code and return the expression.
 print | `(print "hello world")` | `"hello world"null` | Print expression on the screen. Print returns null (which is shown due to the extra print in repl). Give optional second argument as `true` to show strings in readable format.
 error | `(error "invalid value")` | `error: invalid value` | Throw an exception with message as argument.
@@ -266,6 +267,8 @@ floor | `(floor 2.5)` | `2` | Get the next lowest integer.
 ceil  | `(ceil 2.5)` | `3` | Get the next highest integer.
 pow   | `(pow 2 4)` | `16` | Raise the first argument to the power of the second argument.
 sqrt  | `(sqrt 2)` | `1.41` | Calculate the square root.
+coinflip | `(coinflip)` | `true` | Return true or false with equal probability.
+rand  | `(rand 5 10)` | `8` | Return a random integer between given min and max values.
 
 ### String functions
 
diff --git a/src/Lib/Math.php b/src/Lib/Math.php
index f7cacb7..f1f92b3 100644
--- a/src/Lib/Math.php
+++ b/src/Lib/Math.php
@@ -99,5 +99,15 @@ class Math implements ILib
         $env->set('sqrt', new CoreFunc('sqrt', 'Return the square root of the arguemnt.', 1, 1,
             fn ($a) => sqrt($a)
         ));
+
+        // Random number generator
+
+        $env->set('coinflip', new CoreFunc('coinflip', 'Return true or false with equal probability.', 0, 0,
+            fn () => boolval(mt_rand(0, 1))
+        ));
+
+        $env->set('rand', new CoreFunc('rand', 'Return a random integer between given min and max values.', 2, 2,
+            fn ($min, $max) => mt_rand($min, $max)
+        ));
     }
 }
diff --git a/src/LispFactory.php b/src/LispFactory.php
index b562b5c..cb870bf 100644
--- a/src/LispFactory.php
+++ b/src/LispFactory.php
@@ -24,6 +24,15 @@ class LispFactory
             }
         ));
 
+        $env->set('loop', new CoreFunc('loop', 'Call the given function repeatedly in a loop until it returns false.', 1, -1,
+            function (Func $f, ...$args) {
+                do {
+                    $result = $f->call($args);
+                } while ($result);
+                return $result;
+            }
+        ));
+
         $env->set('read', new CoreFunc('read', 'Read string as code.', 1, 1,
             fn (string $a) => $reader->read($tokenizer->tokenize($a))
         ));