storable-record: Elegant definition of Storable instances for records
With this package definition you can build a Storable instance of a record type from Storable instances of its elements. This is as simple as:
import Foreign.Storable.Record as Store import Foreign.Storable (Storable (..), ) import Control.Applicative (liftA2, ) data Stereo a = Stereo (left, right :: a) -- parentheses must be curly braces, but Haddock does not like them store :: Storable a => Store.Dictionary (Stereo a) store = Store.run $ liftA2 Stereo (Store.element left) (Store.element right) instance (Storable a) => Storable (Stereo a) where sizeOf = Store.sizeOf store alignment = Store.alignment store peek = Store.peek store poke = Store.poke store
I cannot promise that the generated memory layout is compatible with that of a corresponding C struct. However, the module generates the smallest layout that is possible with respect to the alignment of the record elements. Thus this package might provide a Haskell98 alternative to HSC without a preprocessor. If you encounter, that a record does not have a compatible layout, we should fix that. But also without C compatibility this package is useful e.g. in connection with StorableVector.
Stereo constructor is exclusively used
for constructing the
where as the accessors in the
are used for assembling the
It is required that the order of arguments of
matches the record accessors in the
If you want that the stored data correctly and fully represents
your Haskell data, it must hold:
Stereo (left x) (right x) = x .
Unfortunately this cannot be checked automatically.
However, mismatching types that are caused by swapped arguments
are detected by the type system.
Our system performs for you:
Size and alignment computation, poking and peeking.
Thus several inconsistency bugs can be prevented using this package,
like size mismatches space required by
There is no more restriction,
thus smart constructors and accessors
and nested records work, too.
For nested records however,
I recommend individual Storable instances for the sub-records.
You see it would simplify class instantiation if we could tell the class dictionary at once instead of defining each method separately.
For examples see packages sox and synthesizer.
|Versions [faq]||0.0.1, 0.0.2, 0.0.2.1, 0.0.2.2, 0.0.2.3, 0.0.2.4, 0.0.2.5, 0.0.3, 0.0.3.1, 0.0.4, 0.0.4.1, 0.0.5|
|Dependencies||base (>=1.0 && <2 || >=3), special-functors (==1.0.*), transformers (>=0.0.1 && <0.2), utility-ht (>=0.0.1 && <0.1) [details]|
|Author||Henning Thielemann <email@example.com>|
|Maintainer||Henning Thielemann <firstname.lastname@example.org>|
|Source repo||head: darcs get http://code.haskell.org/~thielema/storable-record/
this: darcs get http://code.haskell.org/~thielema/storable-record/ --tag 0.0.1
|Uploaded||by HenningThielemann at 2009-05-26T11:46:15Z|
|Distributions||Arch:0.0.5, Debian:0.0.4, LTSHaskell:0.0.4, NixOS:0.0.5, Stackage:0.0.4|
|Downloads||18396 total (202 in the last 30 days)|
|Rating||(no votes yet) [estimated by Bayesian average]|
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