This is probably not really for the libraries list, but in the same vein as this discussion, I think it would be extremely helpful to have a way of banning functions that does *not* require changing the upstream library. I would be thrilled to have a machine-checked ban on use of the 'head', 'tail', etc. On Fri, Aug 31, 2018 at 11:36 AM Henrik Nilsson < Henrik.Nilsson@nottingham.ac.uk> wrote:
Hi,
Richard Eisenberg wrote:
Maybe here's a concrete example:
-- | /Contains a call to 'error'./ Extract the first element of a list, which must be non-empty. head :: [a] -> a
In the end, it's the call to error that I want noted.
Yes, whether the code of a function directly or indirectly calls "error" is well-defined property that could be documented.
But note that this does not coincide with the following:
I think we want something like "partial even given input you can successfully DeepSeq"
That's the specification of the feature I'm after
Consider e.g.
apply f x = f x
As e.g.
apply head [] == _|_
we'd have to conclude by the above definition that "apply" is partial. But it clearly does not "call error".
Just to be clear, this does not correspond to how I understand partiality. Lots of higher order functions, like "map", then would have to called partial. And I am not sure that would be so helpful for the purpose of alerting (new) programmers to functions that one might argue should be avoided.
So maybe something very clear and easy to understand, such as "contains call to error" is the best approach.
Best,
/Henrik
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