Add DiceBag and tests

closes #7

src/DiceBag.php

@@ -0,0 +1,34 @@
+<?php
+declare(strict_types=1);
+
+namespace LotGD\Core;
+
+class DiceBag {
+  public function chance(float $p): bool {
+    $r = $this->uniform(0., 1.);
+    return $r < $p;
+  }
+
+  public function uniform(float $min, float $max): float {
+    return (mt_rand(0, 100) / 100.0) * ($max - $min) + $min;
+  }
+
+  public function normal(float $min, float $max): float {
+    if ($min > $max) {
+      $tmp = $max;
+      $max = $min;
+      $min = $tmp;
+    } else if ($min == $max) {
+      return $min;
+    }
+
+    $mean = ($max - $min) / 2;
+    $r = 0;
+    do {
+      $u1 = mt_rand() / mt_getrandmax();
+      $u2 = mt_rand() / mt_getrandmax();
+      $r = sqrt(-2 * log($u1)) * cos(2 * pi() * $u2) + $mean;
+    } while ($r < $min || $r > $max);
+    return $r;
+  }
+}

tests/DiceBagTest.php

@@ -0,0 +1,32 @@
+<?php
+declare(strict_types=1);
+
+namespace LotGD\Core\Tests;
+
+use LotGD\Core\DiceBag;
+
+/**
+* @backupGlobals disabled
+* @backupStaticAttributes disabled
+*/
+class DiceBagTests extends \PHPUnit_Framework_TestCase {
+  public function testUniform() {
+    $db = new DiceBag();
+    $value = $db->uniform(0., 1.);
+    $this->assertGreaterThan(0, $value);
+    $this->assertLessThan(1, $value);
+  }
+
+  public function testNormal() {
+    $db = new DiceBag();
+    $value = $db->normal(0., 1.);
+    $this->assertGreaterThan(0, $value);
+    $this->assertLessThan(1, $value);
+
+    $value = $db->normal(1., 0.);
+    $this->assertGreaterThan(0, $value);
+    $this->assertLessThan(1, $value);
+
+    $this->assertEquals(0, $db->normal(0., 0.));
+  }
+}