Added {,un}currySigma to Data.Singletons.Sigma #360
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RyanGlScott
requested changes
Aug 27, 2018
RyanGlScott
requested changes
Sep 2, 2018
| @@ -60,6 +61,46 @@ projSigma1 (a :&: _) = fromSing a | |||
| projSigma2 :: forall s t r. (forall (fst :: s). t @@ fst -> r) -> Sigma s t -> r | |||
| projSigma2 f ((_ :: Sing (fst :: s)) :&: b) = f @fst b | |||
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| -- | One half to witnessing an isomorphism. Convert a uncurried | |||
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This is looking better. However, this states that this forms one half of an isomorphism, but doesn't explain what the isomorphism is until much later in the Haddocks.
To make this flow better, I would prefer to structure the Haddocks like so:
Convert an uncurried function on 'Sigma' to a curried one.(Note my use ofanthere—you mistakenly usedainstead.)-
Together, 'currySigma' and 'uncurrySigma' witness an isomorphism such that the following identities hold: <code as before>
| -> (forall (a::k). Sing a -> f@@a -> b) | ||
| currySigma f sing fa = f (sing :&: fa) | ||
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| -- | Elimination of 'Sigma'. Second half of isomorphism. |
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Again, I'd prefer to reorganize this (especially to be in tandem with the Haddocks for currySigma). Something like:
Convert a curried function to a function on 'Sigma'. (In other words, this is an elimination form for 'Sigma'.)Together, 'currySigma' and 'uncurrySigma' witness an isomorphism. (Refer to the documentation for 'currySigma' for more details.)
| -- | One half to witnessing an isomorphism. Convert a uncurried | ||
| -- function on 'Sigma' to a curried one. | ||
| -- | ||
| -- Alternative type |
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I hate to say this, but I really don't think that we should bother putting this alternative type in here, for two reasons:
- Without any context, this new type for
currySigmawon't be much more enlightening than the current type. - It order to actually give the new type some context, we'd need to include some sort of exposition on how
SigmaandConstSym1form a type-level adjunction. But I don't think that the understanding that most readers would gain from this would justify the sheer amount of jargon and prose needed to explain it.
In short, I'd favor just leaving this part out entirely. (Similarly for uncurrySigma.)
RyanGlScott
requested changes
Sep 18, 2018
| @@ -3,6 +3,8 @@ Changelog for singletons project | |||
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| 2.5 | |||
| --- | |||
| * Add `currySigma` and `uncurrySigma` to `Data.Singletons.Sigma`. | |||
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Unfortunately, this didn't make the time window for the 2.5 release. Can you move this to a new next section?
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Any updates on this, @Icelandjack? |
RyanGlScott
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Jul 11, 2019
* `SSigma`, the singleton type for `Sigma`, has been added. This fixes #366. * A `Show` instance has been added for `Sigma` (and `SSigma`) by using copious amounts of quantified constraints. The behavior of these instances closely resembles the `Show` implementation for `DPair` in Idris' standard library: https://github.com/idris-lang/Idris-dev/blob/dbe521ff74189df85121abe454f86894de7fd75c/libs/prelude/Prelude/Show.idr#L195-L196 * New functions `fstSigma` and `sndSigma` (as well as their type-level counterparts) have been added. To avoid being a duplicate of `fstSigma`, `projSigma1` has been redefined to have a new type signature that uses continuation-passing style, much like its cousin `projSigma2`. * New functions `currySigma` and `uncurrySigma` have been added. This fixes #359 and supersedes #360.
RyanGlScott
added a commit
that referenced
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Jul 12, 2019
* `SSigma`, the singleton type for `Sigma`, has been added. This fixes #366. * A `Show` instance has been added for `Sigma` (and `SSigma`) by using copious amounts of quantified constraints. The behavior of these instances closely resembles the `Show` implementation for `DPair` in Idris' standard library: https://github.com/idris-lang/Idris-dev/blob/dbe521ff74189df85121abe454f86894de7fd75c/libs/prelude/Prelude/Show.idr#L195-L196 * New functions `fstSigma` and `sndSigma` (as well as their type-level counterparts) have been added. To avoid being a duplicate of `fstSigma`, `projSigma1` has been redefined to have a new type signature that uses continuation-passing style, much like its cousin `projSigma2`. * New functions `currySigma` and `uncurrySigma` have been added. This fixes #359 and supersedes #360.
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Superseded by #400. |
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Pull request for #359