Expression

Inherits: RefCounted < Object

A class that stores an expression you can execute.

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 LineEdit node to write our expression and show the result.

    var expression = Expression.new()

    func _ready():
        $LineEdit.text_submitted.connect(self._on_text_submitted)

    func _on_text_submitted(command):
        var error = expression.parse(command)
        if error != OK:
            print(expression.get_error_text())
            return
        var result = expression.execute()
        if not expression.has_execute_failed():
            $LineEdit.text = str(result)

    private Expression _expression = new Expression();

    public override void _Ready()
    {
        GetNode<LineEdit>("LineEdit").TextSubmitted += OnTextEntered;
    }

    private void OnTextEntered(string command)
    {
        Error error = _expression.Parse(command);
        if (error != Error.Ok)
        {
            GD.Print(_expression.GetErrorText());
            return;
        }
        Variant result = _expression.Execute();
        if (!_expression.HasExecuteFailed())
        {
            GetNode<LineEdit>("LineEdit").Text = result.ToString();
        }
    }

Tutorials

• Evaluating Expressions

Methods

Variant	execute\ (\ inputs: Array = [], base_instance: Object = null, show_error: bool = true, const_calls_only: bool = false\ )
String	get_error_text\ (\ ) const
bool	has_execute_failed\ (\ ) const
Error	parse\ (\ expression: String, input_names: PackedStringArray = PackedStringArray()\ )

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Method Descriptions

Variant execute\ (\ inputs: Array = [], base_instance: Object = null, show_error: bool = true, const_calls_only: bool = false\ ) 🔗

Executes the expression that was previously parsed by parse() and returns the result. Before you use the returned object, you should check if the method failed by calling has_execute_failed().

If you defined input variables in parse(), you can specify their values in the inputs array, in the same order.

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String get_error_text\ (\ ) const 🔗

Returns the error text if parse() or execute() has failed.

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bool has_execute_failed\ (\ ) const 🔗

Returns true if execute() has failed.

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Error parse\ (\ expression: String, input_names: PackedStringArray = PackedStringArray()\ ) 🔗

Parses the expression and returns an Error code.

You can optionally specify names of variables that may appear in the expression with input_names, so that you can bind them when it gets executed.