- ...

class/LogicFunction.php

@@ -15,6 +15,11 @@ class LogicFunction implements JsonSerializable
         return str_replace(["/", "!", "*", "+"], ["~", "~", "&", "|"], $expression);
     }
 
+    public static function adaptToEL(string $expression): string
+    {
+        return str_replace(["~"], [" not "], $expression);
+    }
+
     public static function collectVariables(string $expression): array
     {
         preg_match_all("/\w/", $expression, $variables);
@@ -41,7 +46,7 @@ class LogicFunction implements JsonSerializable
             $vars[$var] = 0;
         }
 
-        $expression = $this->getExpression("verilog_logic");
+        $expression = self::adaptToEL($this->getExpression("verilog_logic"));
 //        printf("Cooked: %s\n", $cooked_form);
 
         $tt = [];
@@ -171,7 +176,7 @@ class LogicFunction implements JsonSerializable
     public function isValid(): bool
     {
         try {
-            self::$EXP_LANG->lint($this->expression, $this->input_vars);
+            self::$EXP_LANG->lint(self::adaptToEL($this->expression), $this->input_vars);
         } catch (Exception $e) {
             return false;
         }
@@ -248,9 +253,10 @@ class LogicFunction implements JsonSerializable
         return join(" | ", $minterms);
     }
 
-    public function drawNetwork(string $outvar = "f"): string {
+    public function drawNetwork(string $outvar = "f"): string
+    {
         $expr = str_replace(["^"], [" xor "], $this->getExpression());
-        return PythonUtils::execPy("draw_logic_network.py", [ $expr, $outvar ]);
+        return PythonUtils::execPy("draw_logic_network.py", [$expr, $outvar]);
     }
 }
 

class/Tasks/SingleChoiceTask.php

@@ -27,6 +27,10 @@ class SingleChoiceTask extends PicturedTask
         $this->answers[] = $answer;
     }
 
+    function clearAnswers(): void {
+        $this->answers = [];
+    }
+
     function getAnswers(): array
     {
         return $this->answers;