CRM_Utils_Array::product() - Helper to generate Cartesian products

CRM/Utils/Array.php

@@ -635,5 +635,48 @@ class CRM_Utils_Array {
     }
     return $default;
   }
+
+  /**
+   * Generate the Cartesian product of zero or more vectors
+   *
+   * @param array $dimensions list of dimensions to multiply; each key is a dimension name; each value is a vector
+   * @param array $template a base set of values included in every output
+   * @return array each item is a distinct combination of values from $dimensions
+   *
+   * For example, the product of
+   * {
+   *   fg => {red, blue},
+   *   bg => {white, black}
+   * }
+   * would be
+   * {
+   *   {fg => red, bg => white},
+   *   {fg => red, bg => black},
+   *   {fg => blue, bg => white},
+   *   {fg => blue, bg => black}
+   * }
+   */
+  static function product($dimensions, $template = array()) {
+    if (empty($dimensions)) {
+      return array($template);
+    }
+
+    foreach ($dimensions as $key => $value) {
+      $firstKey = $key;
+      $firstValues = $value;
+      break;
+    }
+    unset($dimensions[$key]);
+
+    $results = array();
+    foreach ($firstValues as $firstValue) {
+      foreach (self::product($dimensions, $template) as $result) {
+        $result[$firstKey] = $firstValue;
+        $results[] = $result;
+      }
+    }
+
+    return $results;
+  }
 }
 

tests/phpunit/CRM/Utils/ArrayTest.php

@@ -33,7 +33,7 @@ class CRM_Utils_ArrayTest extends CiviUnitTestCase {
     $inputs[] = array(
       'lang' => 'en',
       'msgid' => 'greeting',
-      'familiar' => false,
+      'familiar' => FALSE,
       'value' => 'Hello'
     );
     $inputs[] = array(
@@ -54,7 +54,7 @@ class CRM_Utils_ArrayTest extends CiviUnitTestCase {
     $inputs[] = array(
       'lang' => 'en',
       'msgid' => 'greeting',
-      'familiar' => true,
+      'familiar' => TRUE,
       'value' => 'Hey'
     );
 
@@ -82,4 +82,41 @@ class CRM_Utils_ArrayTest extends CiviUnitTestCase {
     $this->assertEquals($expected, CRM_Utils_Array::collect('catWord', $arr));
   }
 
+  function testProduct0() {
+    $actual = CRM_Utils_Array::product(
+      array(),
+      array('base data' => 1)
+    );
+    $this->assertEquals(array(
+      array('base data' => 1),
+    ), $actual);
+  }
+
+  function testProduct1() {
+    $actual = CRM_Utils_Array::product(
+      array('dim1' => array('a', 'b')),
+      array('base data' => 1)
+    );
+    $this->assertEquals(array(
+      array('base data' => 1, 'dim1' => 'a'),
+      array('base data' => 1, 'dim1' => 'b'),
+    ), $actual);
+  }
+
+  function testProduct3() {
+    $actual = CRM_Utils_Array::product(
+      array('dim1' => array('a', 'b'), 'dim2' => array('alpha', 'beta'), 'dim3' => array('one', 'two')),
+      array('base data' => 1)
+    );
+    $this->assertEquals(array(
+      array('base data' => 1, 'dim1' => 'a', 'dim2' => 'alpha', 'dim3' => 'one'),
+      array('base data' => 1, 'dim1' => 'a', 'dim2' => 'alpha', 'dim3' => 'two'),
+      array('base data' => 1, 'dim1' => 'a', 'dim2' => 'beta', 'dim3' => 'one'),
+      array('base data' => 1, 'dim1' => 'a', 'dim2' => 'beta', 'dim3' => 'two'),
+      array('base data' => 1, 'dim1' => 'b', 'dim2' => 'alpha', 'dim3' => 'one'),
+      array('base data' => 1, 'dim1' => 'b', 'dim2' => 'alpha', 'dim3' => 'two'),
+      array('base data' => 1, 'dim1' => 'b', 'dim2' => 'beta', 'dim3' => 'one'),
+      array('base data' => 1, 'dim1' => 'b', 'dim2' => 'beta', 'dim3' => 'two'),
+    ), $actual);
+  }
 }