GDLambda is a small, pure GDScript library adding lambdas and basic functional programming features to Godot 3.

Most of these are already available in GDScript 2.0, but at the time of writing this Godot 4 is still not a stable release.

Copy addons/gdlambda directory into the addons directory of your project.

var lambda := gdl.lambda("func(x): return x*x*x")
print(lambda.execute(4)) # 64

var units := get_children()
units.sort_custom( # sort units by their initiative
    gdl.lambda("func(a, b): return a.initiative > b.initiative").as_funcref(),
    "call_func"
)

See examples.gd.

Generally yes. Just DON'T concatenate lambda source with any kind of user input. Doing so can be highly dangerous and allow cheating or remote code execution, which is a huge no no. Think of eval method from JavaScript. Godot's built-in Expression has a similar problem, when you want to "capture" its environment, although it can't access any built-in classes, only methods, variables and constants of a captured object (which can still cause some considerable issues, when implemented in a wrong way), whereas lambdas can access and instance any built-in class as well as singletons.

To be safe: If you want to have an access to any external variables ONLY pass them as arguments or capture them using Dictionary (see examples.gd) and NEVER insert any user-defined strings into lambda source (again, think of eval from JavaScript).

I don't know lol. I just wrote it for fun in a few hours and it turned out to be less confusing and error-prone than I initially imagined, so I added comments here and there and a few examples and made this repository. When Godot 4 is stable, this will be pretty much useless, but again, it's more of an experimental thing.

See LICENSE