On 14/05/11 17:40, Nicolas Pouillard wrote:
On Sat, 14 May 2011 15:06:51 +1000, Reiner Pope<[email protected]> wrote:
Hi all,
Is there a policy for strictness of datatypes in Yi, and what is it?
Specifically:
1. When I write a datatype, which fields should I make strict? For
instance, all fields in Editor are strict, and all fields except
'height' and 'winRegion' in Window are strict. Is there some
reasoning underlying this?
2. What should I do to ensure strictness of lazy datatypes like [a]?
For instance, the 'bufAccessList :: ![BufferRef]' field of
'Window' is marked strict, but is a list. Is it the client's duty
to ensure that this list is fully evaluated?
Would there be any objections to using the 'deepseq' package to ensure
evaluation? The 'NFData' class is supported by Derive, so it might be
possible to generate many instances automatically.
I would recommend to use a strict-by-default datastructure instead of lazy
lists plus NFData. This is not against NFData which is very useful but it
traverses the whole list each time even when the list is already forced.
What about Data.Sequence or Data.FingerTree ?
Indeed, strict datastructures seem the right solution.
However, Data.Sequence and Data.FingerTree aren't strict enough. Both of
them are only spine-strict, so that
singleton undefined `seq` () = ()
Likewise for most other containers, such as Data.Map.
Cheers,
Reiner
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