Data commit

Task/Ternary-logic/PHP/ternary-logic.php

@@ -0,0 +1,61 @@
+#!/usr/bin/php
+<?php
+
+# defined as numbers, so I can use max() and min() on it
+if (! define('triFalse',0))  trigger_error('Unknown error defining!', E_USER_ERROR);
+if (! define('triMaybe',1))  trigger_error('Unknown error defining!', E_USER_ERROR);
+if (! define('triTrue', 2))  trigger_error('Unknown error defining!', E_USER_ERROR);
+
+$triNotarray = array(triFalse=>triTrue, triMaybe=>triMaybe, triTrue=>triFalse);
+
+# output helper
+function triString ($tri) {
+    if ($tri===triFalse) return 'false  ';
+    if ($tri===triMaybe) return 'unknown';
+    if ($tri===triTrue)  return 'true   ';
+    trigger_error('triString: parameter not a tri value', E_USER_ERROR);
+}
+
+function triAnd() {
+    if (func_num_args() < 2)
+       trigger_error('triAnd needs 2 or more parameters', E_USER_ERROR);
+    return min(func_get_args());
+}
+
+function triOr() {
+    if (func_num_args() < 2)
+       trigger_error('triOr needs 2 or more parameters', E_USER_ERROR);
+    return max(func_get_args());
+}
+
+function triNot($t) {
+    global $triNotarray; # using result table
+    if (in_array($t, $triNotarray)) return $triNotarray[$t];
+    trigger_error('triNot: Parameter is not a tri value', E_USER_ERROR);
+}
+
+function triImplies($a, $b) {
+    if ($a===triFalse || $b===triTrue)  return triTrue;
+    if ($a===triMaybe || $b===triMaybe) return triMaybe;
+    # without parameter type check I just would return triFalse here
+    if ($a===triTrue &&  $b===triFalse) return triFalse;
+    trigger_error('triImplies: parameter type error', E_USER_ERROR);
+}
+
+function triEquiv($a, $b) {
+    if ($a===triTrue)  return $b;
+    if ($a===triMaybe) return $a;
+    if ($a===triFalse) return triNot($b);
+    trigger_error('triEquiv: parameter type error', E_USER_ERROR);
+}
+
+# data sampling
+
+printf("--- Sample output for a equivalent b ---\n\n");
+
+foreach ([triTrue,triMaybe,triFalse] as $a) {
+    foreach ([triTrue,triMaybe,triFalse] as $b) {
+        printf("for a=%s and b=%s a equivalent b is %s\n",
+               triString($a), triString($b), triString(triEquiv($a, $b)));
+    }
+}