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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())

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.

String get_error_text() const 🔗

Returns the error text if parse or execute has failed.

bool has_execute_failed() const 🔗

Returns true if execute has failed.

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.