Are closures not supported?

[mmontone]

Hi. Are closures not supported?

The following code all gives: UnboundLocalError: local variable 'x' referenced before assignment:

Reading a variable from closure context:

(setv my-closure
      (let [x 0]
        (fn []
          x)))

(my-closure)

=> UnboundLocalError: local variable 'x' referenced before assignment

Setting a variable in closure context:

(setv my-closure
      (let [x 0]
        (fn []
          (setv x (+ x 1))
          x)))

(my-closure)

=> UnboundLocalError: local variable 'x' referenced before assignment

[Kodiologist]

Yes, closures are supported. Any Python code using closures will work the same if translated into Hy.

Your first example doesn't work because there's no built-in macro named setf. Note that the error message is actually NameError: name 'setf' is not defined, not UnboundLocalError.

Your second example doesn't work because your function tries to set x, which means it will create a new local variable for x, which is unset by the time of (+ x 1). Use (nonlocal x) to avoid this. In general, I'd recommend mastering Python scoping before trying to use let, which complicates things.

[mmontone]

Ok. Thanks. I'll have a look.

What do you mean with the setf in the first example? I'm just trying to read a variable introduced with the let, there's not variable setting.

[mmontone]

Sorry. I changed the code there. I mis typed.

[mmontone]

It works after nonlocal! Thanks!