Sync classref with current source

classes/class_expression.rst

@@ -14,7 +14,7 @@ Expression
 Brief Description
 -----------------
 
-
+A class that stores an expression you can execute.
 
 Methods
 -------
@@ -29,6 +29,31 @@ Methods
 | :ref:`Error<enum_@GlobalScope_Error>`  | :ref:`parse<class_Expression_parse>` **(** :ref:`String<class_String>` expression, :ref:`PoolStringArray<class_PoolStringArray>` input_names=PoolStringArray(  ) **)**              |
 +----------------------------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
 
+Description
+-----------
+
+An expression can be made of any arithmetic operation, built-in math function call, method call of a passed instance, or built-in type construction call.
+
+An example expression text using the built-in math functions could be ``sqrt(pow(3,2) + pow(4,2))``.
+
+In the following example we use a :ref:`LineEdit<class_LineEdit>` node to write our expression and show the result.
+
+::
+
+    onready var expression = Expression.new()
+    
+    func _ready():
+        $LineEdit.connect("text_entered", self, "_on_text_entered")
+    
+    func _on_text_entered(command):
+        var error = expression.parse(command, [])
+        if error != OK:
+            print(get_error_text())
+            return
+        var result = expression.execute([], null, true)
+        if not expression.has_execute_failed():
+            $LineEdit.text = str(result)
+
 Method Descriptions
 -------------------
 
@@ -36,15 +61,23 @@ Method Descriptions
 
 - :ref:`Variant<class_Variant>` **execute** **(** :ref:`Array<class_Array>` inputs=[  ], :ref:`Object<class_Object>` base_instance=null, :ref:`bool<class_bool>` show_error=true **)**
 
+Executes the expression that was previously parsed by :ref:`parse<class_Expression_parse>` and returns the result. Before you use the returned object, you should check if the method failed by calling :ref:`has_execute_failed<class_Expression_has_execute_failed>`.
+
 .. _class_Expression_get_error_text:
 
 - :ref:`String<class_String>` **get_error_text** **(** **)** const
 
+Returns the error text if :ref:`parse<class_Expression_parse>` has failed.
+
 .. _class_Expression_has_execute_failed:
 
 - :ref:`bool<class_bool>` **has_execute_failed** **(** **)** const
 
+Returns ``true`` if :ref:`execute<class_Expression_execute>` has failed.
+
 .. _class_Expression_parse:
 
 - :ref:`Error<enum_@GlobalScope_Error>` **parse** **(** :ref:`String<class_String>` expression, :ref:`PoolStringArray<class_PoolStringArray>` input_names=PoolStringArray(  ) **)**
 
+Parses the expression and returns a :ref:`Error<enum_@GlobalScope_Error>`.
+