Re: leakproof

On Feb 19, 2012, at 7:24 PM, Tom Lane wrote:

> Don Baccus <dhogaza(at)pacifier(dot)com> writes:
>> On Feb 19, 2012, at 5:42 PM, Tom Lane wrote:
>>> Hmm, "pure" doesn't sound bad to me. Nice and short.
>
>> Technically, "pure" is stronger than "has no side effects":
>> http://en.wikipedia.org/wiki/Pure_function
>> Result can't depend on state (for instance, database contents), either. This is the typical definition used in functional programming.
>
> Well, that condition is subsumed in our idea of an immutable function.

Yes, I said that myself, perhaps you didn't bother to read closely?

> It's not clear to me whether pure/leakproof functions are meant to be a
> strict subset of immutable functions

Superset, not subset, unless my guessing is wrong. How could "pure" be a subset of "immutable"?

OK, at this point, proponents will explain why ...

But if you're not clear as to what a "leakproof" function is meant to be. then I suggest the definition must be defined very clearly, so everyone understands what it is meant to be.

> , but if they are then they meet
> this stricter definition. On the other hand, if pure/leakproof functions
> don't have to be immutable but only stable, then the stricter definition
> corresponds to "pure immutable". That still doesn't sound too bad, as
> long as we define our terms clearly in the docs.

Sure, let those making the proposal make things clear.

Just speaking as a gadfly who's not posted here for probably close on 10 years …

----
Don Baccus
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