Extract DELTA() and GESTEP() functions from the Engineering class into a dedicated Comparison classes

src/PhpSpreadsheet/Calculation/Calculation.php

@@ -839,7 +839,7 @@ class Calculation
         ],
         'DELTA' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'DELTA'],
+            'functionCall' => [Engineering\Compare::class, 'DELTA'],
             'argumentCount' => '1,2',
         ],
         'DEVSQ' => [
@@ -954,7 +954,7 @@ class Calculation
         ],
         'ERFC.PRECISE' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'ERFC'],
+            'functionCall' => [Engineering\ErfC::class, 'ERFC'],
             'argumentCount' => '1',
         ],
         'ERROR.TYPE' => [
@@ -1196,7 +1196,7 @@ class Calculation
         ],
         'GESTEP' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'GESTEP'],
+            'functionCall' => [Engineering\Compare::class, 'GESTEP'],
             'argumentCount' => '1,2',
         ],
         'GETPIVOTDATA' => [

src/PhpSpreadsheet/Calculation/Engineering.php

@@ -1091,24 +1091,23 @@ public static function IMPRODUCT(...$complexNumbers)
      * DELTA.
      *
      * Tests whether two values are equal. Returns 1 if number1 = number2; returns 0 otherwise.
-     *    Use this function to filter a set of values. For example, by summing several DELTA
-     *    functions you calculate the count of equal pairs. This function is also known as the
-     * Kronecker Delta function.
+     * Use this function to filter a set of values. For example, by summing several DELTA
+     *     functions you calculate the count of equal pairs. This function is also known as the
+     *     Kronecker Delta function.
      *
      *    Excel Function:
      *        DELTA(a[,b])
      *
+     * @Deprecated 2.0.0 Use the DELTA() method in the Engineering\Compare class instead
+     *
      * @param float $a the first number
      * @param float $b The second number. If omitted, b is assumed to be zero.
      *
-     * @return int
+     * @return int|string (string in the event of an error)
      */
     public static function DELTA($a, $b = 0)
     {
-        $a = Functions::flattenSingleValue($a);
-        $b = Functions::flattenSingleValue($b);
-
-        return (int) ($a == $b);
+        return Engineering\Compare::DELTA($a, $b);
     }
 
     /**
@@ -1119,20 +1118,18 @@ public static function DELTA($a, $b = 0)
      *
      *    Returns 1 if number >= step; returns 0 (zero) otherwise
      *    Use this function to filter a set of values. For example, by summing several GESTEP
-     * functions you calculate the count of values that exceed a threshold.
+     *        functions you calculate the count of values that exceed a threshold.
+     *
+     * @Deprecated 2.0.0 Use the GESTEP() method in the Engineering\Compare class instead
      *
      * @param float $number the value to test against step
-     * @param float $step The threshold value.
-     *                                    If you omit a value for step, GESTEP uses zero.
+     * @param float $step The threshold value. If you omit a value for step, GESTEP uses zero.
      *
-     * @return int
+     * @return int|string (string in the event of an error)
      */
     public static function GESTEP($number, $step = 0)
     {
-        $number = Functions::flattenSingleValue($number);
-        $step = Functions::flattenSingleValue($step);
-
-        return (int) ($number >= $step);
+        return Engineering\Compare::GESTEP($number, $step);
     }
 
     /**

src/PhpSpreadsheet/Calculation/Engineering/Compare.php

@@ -0,0 +1,63 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheet\Calculation\Engineering;
+
+use PhpOffice\PhpSpreadsheet\Calculation\Functions;
+
+class Compare
+{
+    /**
+     * DELTA.
+     *
+     *    Excel Function:
+     *        DELTA(a[,b])
+     *
+     *    Tests whether two values are equal. Returns 1 if number1 = number2; returns 0 otherwise.
+     *    Use this function to filter a set of values. For example, by summing several DELTA
+     *        functions you calculate the count of equal pairs. This function is also known as the
+     *        Kronecker Delta function.
+     *
+     * @param float $a the first number
+     * @param float $b The second number. If omitted, b is assumed to be zero.
+     *
+     * @return int|string (string in the event of an error)
+     */
+    public static function DELTA($a, $b = 0)
+    {
+        $a = Functions::flattenSingleValue($a);
+        $b = Functions::flattenSingleValue($b);
+
+        if (!is_numeric($a) || !is_numeric($b)) {
+            return Functions::VALUE();
+        }
+
+        return (int) ($a == $b);
+    }
+
+    /**
+     * GESTEP.
+     *
+     *    Excel Function:
+     *        GESTEP(number[,step])
+     *
+     *    Returns 1 if number >= step; returns 0 (zero) otherwise
+     *    Use this function to filter a set of values. For example, by summing several GESTEP
+     *        functions you calculate the count of values that exceed a threshold.
+     *
+     * @param float $number the value to test against step
+     * @param float $step The threshold value. If you omit a value for step, GESTEP uses zero.
+     *
+     * @return int|string (string in the event of an error)
+     */
+    public static function GESTEP($number, $step = 0)
+    {
+        $number = Functions::flattenSingleValue($number);
+        $step = Functions::flattenSingleValue($step);
+
+        if (!is_numeric($number) || !is_numeric($step)) {
+            return Functions::VALUE();
+        }
+
+        return (int) ($number >= $step);
+    }
+}

tests/data/Calculation/Engineering/DELTA.php

@@ -126,4 +126,9 @@
         1.5,
         1.5,
     ],
+    [
+        '#VALUE!',
+        1,
+        true,
+    ],
 ];

tests/data/Calculation/Engineering/GESTEP.php

@@ -406,4 +406,9 @@
         4.5,
         4.5,
     ],
+    [
+        '#VALUE!',
+        1,
+        true,
+    ],
 ];