Can we have Function.isPure(f)

Herby Vojčík herby at
Mon Nov 5 12:19:54 PST 2012

Irakli Gozalishvili wrote:
>   Hi,
> I keep running into cases where I would like to know if function is
> pure. Although my interpretation of pure is not quite right but I don't
> know any better name. By pure in this context I would refer to functions
> that don't access an out scope variables and don't
> do any mutations of itself or it's properties no references to itself
> could be an option too. My intended use case for such a feature is to

IOW, 'stateless'; or 'serializable'. For in fact it means, that I can 
send f.toString() to the other side and when evaled, I can use it.

> processes too, it would be great if we had something like
> Function.isPure(f). Also as far as I know jits already capture this info
> for optimisation purposes maybe it could be exposed ? Another
> alternative could be pure(function() { …. }) that would throw compile
> error if
> function followed is not pure.

Yes, it could be nice to have some API to help with this. Maybe not 
generic isPure or the like, maybe Function.serialize(f) and 
Function.deserialize(serialized_f) would be enough, the former returning 
null if not pure/stateless/serializable.

It is good to note that the function is serializable not only if it has 
no outer pointers, but also when its outer pointers only point to 'known 
primitives' (numbers, strings, null, true, false; not symbols).

> Thanks!
> --
> Irakli Gozalishvili
> Web:


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