Safe Haskell | None |
---|---|
Language | Haskell2010 |
Classes for generalized combinators on SOP types.
In the SOP approach to generic programming, we're predominantly concerned with four structured datatypes:
NP
:: (k -> *) -> ( [k] -> *) -- n-ary productNS
:: (k -> *) -> ( [k] -> *) -- n-ary sumPOP
:: (k -> *) -> ([[k]] -> *) -- product of productsSOP
:: (k -> *) -> ([[k]] -> *) -- sum of products
All of these have a kind that fits the following pattern:
(k -> *) -> (l -> *)
These four types support similar interfaces. In order to allow reusing the same combinator names for all of these types, we define various classes in this module that allow the necessary generalization.
The classes typically lift concepts that exist for kinds *
or
* -> *
to datatypes of kind (k -> *) -> (l -> *)
. This module
also derives a number of derived combinators.
The actual instances are defined in Generics.SOP.NP and Generics.SOP.NS.
- class HPure h where
- newtype (f -.-> g) a = Fn {
- apFn :: f a -> g a
- fn :: (f a -> f' a) -> (f -.-> f') a
- fn_2 :: (f a -> f' a -> f'' a) -> (f -.-> (f' -.-> f'')) a
- fn_3 :: (f a -> f' a -> f'' a -> f''' a) -> (f -.-> (f' -.-> (f'' -.-> f'''))) a
- fn_4 :: (f a -> f' a -> f'' a -> f''' a -> f'''' a) -> (f -.-> (f' -.-> (f'' -.-> (f''' -.-> f'''')))) a
- type family Prod (h :: (k -> *) -> l -> *) :: (k -> *) -> l -> *
- class (Prod (Prod h) ~ Prod h, HPure (Prod h)) => HAp h where
- hliftA :: (SListIN (Prod h) xs, HAp h) => (forall a. f a -> f' a) -> h f xs -> h f' xs
- hliftA2 :: (SListIN (Prod h) xs, HAp h, HAp (Prod h)) => (forall a. f a -> f' a -> f'' a) -> Prod h f xs -> h f' xs -> h f'' xs
- hliftA3 :: (SListIN (Prod h) xs, HAp h, HAp (Prod h)) => (forall a. f a -> f' a -> f'' a -> f''' a) -> Prod h f xs -> Prod h f' xs -> h f'' xs -> h f''' xs
- hmap :: (SListIN (Prod h) xs, HAp h) => (forall a. f a -> f' a) -> h f xs -> h f' xs
- hzipWith :: (SListIN (Prod h) xs, HAp h, HAp (Prod h)) => (forall a. f a -> f' a -> f'' a) -> Prod h f xs -> h f' xs -> h f'' xs
- hzipWith3 :: (SListIN (Prod h) xs, HAp h, HAp (Prod h)) => (forall a. f a -> f' a -> f'' a -> f''' a) -> Prod h f xs -> Prod h f' xs -> h f'' xs -> h f''' xs
- hcliftA :: (AllN (Prod h) c xs, HAp h) => proxy c -> (forall a. c a => f a -> f' a) -> h f xs -> h f' xs
- hcliftA2 :: (AllN (Prod h) c xs, HAp h, HAp (Prod h)) => proxy c -> (forall a. c a => f a -> f' a -> f'' a) -> Prod h f xs -> h f' xs -> h f'' xs
- hcliftA3 :: (AllN (Prod h) c xs, HAp h, HAp (Prod h)) => proxy c -> (forall a. c a => f a -> f' a -> f'' a -> f''' a) -> Prod h f xs -> Prod h f' xs -> h f'' xs -> h f''' xs
- hcmap :: (AllN (Prod h) c xs, HAp h) => proxy c -> (forall a. c a => f a -> f' a) -> h f xs -> h f' xs
- hczipWith :: (AllN (Prod h) c xs, HAp h, HAp (Prod h)) => proxy c -> (forall a. c a => f a -> f' a -> f'' a) -> Prod h f xs -> h f' xs -> h f'' xs
- hczipWith3 :: (AllN (Prod h) c xs, HAp h, HAp (Prod h)) => proxy c -> (forall a. c a => f a -> f' a -> f'' a -> f''' a) -> Prod h f xs -> Prod h f' xs -> h f'' xs -> h f''' xs
- type family CollapseTo (h :: (k -> *) -> l -> *) (x :: *) :: *
- class HCollapse h where
- class HAp h => HSequence h where
- hsequence :: (SListIN h xs, SListIN (Prod h) xs, HSequence h) => Applicative f => h f xs -> f (h I xs)
- hsequenceK :: (SListIN h xs, SListIN (Prod h) xs, Applicative f, HSequence h) => h (K (f a)) xs -> f (h (K a) xs)
- class HIndex h where
- type family UnProd (h :: (k -> *) -> l -> *) :: (k -> *) -> l -> *
- class UnProd (Prod h) ~ h => HApInjs h where
- class HExpand h where
Generalized applicative functor structure
Generalized pure
hpure :: SListIN h xs => (forall a. f a) -> h f xs Source #
Corresponds to pure
directly.
Instances:
hpure
,pure_NP
::SListI
xs => (forall a. f a) ->NP
f xshpure
,pure_POP
::SListI2
xss => (forall a. f a) ->POP
f xss
hcpure :: AllN h c xs => proxy c -> (forall a. c a => f a) -> h f xs Source #
A variant of hpure
that allows passing in a constrained
argument.
Calling
where hcpure
f ss :: h f xs
causes f
to be
applied at all the types that are contained in xs
. Therefore,
the constraint c
has to be satisfied for all elements of xs
,
which is what
states.AllMap
h c xs
Morally, hpure
is a special case of hcpure
where the
constraint is empty. However, it is in the nature of how AllMap
is defined as well as current GHC limitations that it is tricky
to prove to GHC in general that
is
always satisfied. Therefore, we typically define AllMap
h c NoConstraint xshpure
separately and directly, and make it a member of the class.
Instances:
hcpure
,cpure_NP
:: (All
c xs ) => proxy c -> (forall a. c a => f a) ->NP
f xshcpure
,cpure_POP
:: (All2
c xss) => proxy c -> (forall a. c a => f a) ->POP
f xss
Generalized <*>
fn :: (f a -> f' a) -> (f -.-> f') a Source #
Construct a lifted function.
Same as Fn
. Only available for uniformity with the
higher-arity versions.
fn_2 :: (f a -> f' a -> f'' a) -> (f -.-> (f' -.-> f'')) a Source #
Construct a binary lifted function.
fn_3 :: (f a -> f' a -> f'' a -> f''' a) -> (f -.-> (f' -.-> (f'' -.-> f'''))) a Source #
Construct a ternary lifted function.
fn_4 :: (f a -> f' a -> f'' a -> f''' a -> f'''' a) -> (f -.-> (f' -.-> (f'' -.-> (f''' -.-> f'''')))) a Source #
Construct a quarternary lifted function.
type family Prod (h :: (k -> *) -> l -> *) :: (k -> *) -> l -> * Source #
Maps a structure containing sums to the corresponding product structure.
class (Prod (Prod h) ~ Prod h, HPure (Prod h)) => HAp h where Source #
A generalization of <*>
.
hap :: Prod h (f -.-> g) xs -> h f xs -> h g xs Source #
Corresponds to <*>
.
For products (NP
) as well as products of products
(POP
), the correspondence is rather direct. We combine
a structure containing (lifted) functions and a compatible structure
containing corresponding arguments into a compatible structure
containing results.
The same combinator can also be used to combine a product structure of functions with a sum structure of arguments, which then results in another sum structure of results. The sum structure determines which part of the product structure will be used.
Instances:
hap
,ap_NP
::NP
(f -.-> g) xs ->NP
f xs ->NP
g xshap
,ap_NS
::NP
(f -.-> g) xs ->NS
f xs ->NS
g xshap
,ap_POP
::POP
(f -.-> g) xss ->POP
f xss ->POP
g xsshap
,ap_SOP
::POP
(f -.-> g) xss ->SOP
f xss ->SOP
g xss
Derived functions
hliftA :: (SListIN (Prod h) xs, HAp h) => (forall a. f a -> f' a) -> h f xs -> h f' xs Source #
A generalized form of liftA
,
which in turn is a generalized map
.
Takes a lifted function and applies it to every element of a structure while preserving its shape.
Specification:
hliftA
f xs =hpure
(fn
f) `hap
` xs
Instances:
hliftA
,liftA_NP
::SListI
xs => (forall a. f a -> f' a) ->NP
f xs ->NP
f' xshliftA
,liftA_NS
::SListI
xs => (forall a. f a -> f' a) ->NS
f xs ->NS
f' xshliftA
,liftA_POP
::SListI2
xss => (forall a. f a -> f' a) ->POP
f xss ->POP
f' xsshliftA
,liftA_SOP
::SListI2
xss => (forall a. f a -> f' a) ->SOP
f xss ->SOP
f' xss
hliftA2 :: (SListIN (Prod h) xs, HAp h, HAp (Prod h)) => (forall a. f a -> f' a -> f'' a) -> Prod h f xs -> h f' xs -> h f'' xs Source #
A generalized form of liftA2
,
which in turn is a generalized zipWith
.
Takes a lifted binary function and uses it to combine two structures of equal shape into a single structure.
It either takes two product structures to a product structure, or one product and one sum structure to a sum structure.
Specification:
hliftA2
f xs ys =hpure
(fn_2
f) `hap
` xs `hap
` ys
Instances:
hliftA2
,liftA2_NP
::SListI
xs => (forall a. f a -> f' a -> f'' a) ->NP
f xs ->NP
f' xs ->NP
f'' xshliftA2
,liftA2_NS
::SListI
xs => (forall a. f a -> f' a -> f'' a) ->NP
f xs ->NS
f' xs ->NS
f'' xshliftA2
,liftA2_POP
::SListI2
xss => (forall a. f a -> f' a -> f'' a) ->POP
f xss ->POP
f' xss ->POP
f'' xsshliftA2
,liftA2_SOP
::SListI2
xss => (forall a. f a -> f' a -> f'' a) ->POP
f xss ->SOP
f' xss ->SOP
f'' xss
hliftA3 :: (SListIN (Prod h) xs, HAp h, HAp (Prod h)) => (forall a. f a -> f' a -> f'' a -> f''' a) -> Prod h f xs -> Prod h f' xs -> h f'' xs -> h f''' xs Source #
A generalized form of liftA3
,
which in turn is a generalized zipWith3
.
Takes a lifted ternary function and uses it to combine three structures of equal shape into a single structure.
It either takes three product structures to a product structure, or two product structures and one sum structure to a sum structure.
Specification:
hliftA3
f xs ys zs =hpure
(fn_3
f) `hap
` xs `hap
` ys `hap
` zs
Instances:
hliftA3
,liftA3_NP
::SListI
xs => (forall a. f a -> f' a -> f'' a -> f''' a) ->NP
f xs ->NP
f' xs ->NP
f'' xs ->NP
f''' xshliftA3
,liftA3_NS
::SListI
xs => (forall a. f a -> f' a -> f'' a -> f''' a) ->NP
f xs ->NP
f' xs ->NS
f'' xs ->NS
f''' xshliftA3
,liftA3_POP
::SListI2
xss => (forall a. f a -> f' a -> f'' a -> f''' a) ->POP
f xss ->POP
f' xss ->POP
f'' xss ->POP
f''' xshliftA3
,liftA3_SOP
::SListI2
xss => (forall a. f a -> f' a -> f'' a -> f''' a) ->POP
f xss ->POP
f' xss ->SOP
f'' xss ->SOP
f''' xs
hmap :: (SListIN (Prod h) xs, HAp h) => (forall a. f a -> f' a) -> h f xs -> h f' xs Source #
Another name for hliftA
.
Since: 0.2
hzipWith :: (SListIN (Prod h) xs, HAp h, HAp (Prod h)) => (forall a. f a -> f' a -> f'' a) -> Prod h f xs -> h f' xs -> h f'' xs Source #
Another name for hliftA2
.
Since: 0.2
hzipWith3 :: (SListIN (Prod h) xs, HAp h, HAp (Prod h)) => (forall a. f a -> f' a -> f'' a -> f''' a) -> Prod h f xs -> Prod h f' xs -> h f'' xs -> h f''' xs Source #
Another name for hliftA3
.
Since: 0.2
hcliftA :: (AllN (Prod h) c xs, HAp h) => proxy c -> (forall a. c a => f a -> f' a) -> h f xs -> h f' xs Source #
hcliftA2 :: (AllN (Prod h) c xs, HAp h, HAp (Prod h)) => proxy c -> (forall a. c a => f a -> f' a -> f'' a) -> Prod h f xs -> h f' xs -> h f'' xs Source #
hcliftA3 :: (AllN (Prod h) c xs, HAp h, HAp (Prod h)) => proxy c -> (forall a. c a => f a -> f' a -> f'' a -> f''' a) -> Prod h f xs -> Prod h f' xs -> h f'' xs -> h f''' xs Source #
hcmap :: (AllN (Prod h) c xs, HAp h) => proxy c -> (forall a. c a => f a -> f' a) -> h f xs -> h f' xs Source #
Another name for hcliftA
.
Since: 0.2
hczipWith :: (AllN (Prod h) c xs, HAp h, HAp (Prod h)) => proxy c -> (forall a. c a => f a -> f' a -> f'' a) -> Prod h f xs -> h f' xs -> h f'' xs Source #
Another name for hcliftA2
.
Since: 0.2
hczipWith3 :: (AllN (Prod h) c xs, HAp h, HAp (Prod h)) => proxy c -> (forall a. c a => f a -> f' a -> f'' a -> f''' a) -> Prod h f xs -> Prod h f' xs -> h f'' xs -> h f''' xs Source #
Another name for hcliftA3
.
Since: 0.2
Collapsing homogeneous structures
type family CollapseTo (h :: (k -> *) -> l -> *) (x :: *) :: * Source #
Maps products to lists, and sums to identities.
type CollapseTo [[k]] k (POP k) a Source # | |
type CollapseTo [[k]] k (SOP k) a Source # | |
type CollapseTo [k] k (NP k) a Source # | |
type CollapseTo [k] k (NS k) a Source # | |
class HCollapse h where Source #
A class for collapsing a heterogeneous structure into a homogeneous one.
hcollapse :: SListIN h xs => h (K a) xs -> CollapseTo h a Source #
Collapse a heterogeneous structure with homogeneous elements into a homogeneous structure.
If a heterogeneous structure is instantiated to the constant
functor K
, then it is in fact homogeneous. This function
maps such a value to a simpler Haskell datatype reflecting that.
An
contains a single NS
(K
a)a
, and an
contains
a list of NP
(K
a)a
s.
Instances:
hcollapse
,collapse_NP
::NP
(K
a) xs -> [a]hcollapse
,collapse_NS
::NS
(K
a) xs -> ahcollapse
,collapse_POP
::POP
(K
a) xss -> [[a]]hcollapse
,collapse_SOP
::SOP
(K
a) xss -> [a]
Sequencing effects
class HAp h => HSequence h where Source #
A generalization of sequenceA
.
hsequence' :: (SListIN h xs, Applicative f) => h (f :.: g) xs -> f (h g xs) Source #
Corresponds to sequenceA
.
Lifts an applicative functor out of a structure.
Instances:
hsequence'
,sequence'_NP
:: (SListI
xs ,Applicative
f) =>NP
(f:.:
g) xs -> f (NP
g xs )hsequence'
,sequence'_NS
:: (SListI
xs ,Applicative
f) =>NS
(f:.:
g) xs -> f (NS
g xs )hsequence'
,sequence'_POP
:: (SListI2
xss,Applicative
f) =>POP
(f:.:
g) xss -> f (POP
g xss)hsequence'
,sequence'_SOP
:: (SListI2
xss,Applicative
f) =>SOP
(f:.:
g) xss -> f (SOP
g xss)
Derived functions
hsequence :: (SListIN h xs, SListIN (Prod h) xs, HSequence h) => Applicative f => h f xs -> f (h I xs) Source #
Special case of hsequence'
where g =
.I
hsequenceK :: (SListIN h xs, SListIN (Prod h) xs, Applicative f, HSequence h) => h (K (f a)) xs -> f (h (K a) xs) Source #
Special case of hsequence'
where g =
.K
a
Indexing into sums
A class for determining which choice in a sum-like structure a value represents.
hindex :: h f xs -> Int Source #
If h
is a sum-like structure representing a choice
between n
different options, and x
is a value of
type h f xs
, then
returns a number between
hindex
x0
and n - 1
representing the index of the choice
made by x
.
Instances:
hindex
,index_NS
::NS
f xs -> Inthindex
,index_SOP
::SOP
f xs -> Int
Examples:
>>>
hindex (S (S (Z (I False))))
2>>>
hindex (Z (K ()))
0>>>
hindex (SOP (S (Z (I True :* I 'x' :* Nil))))
1
Since: 0.2.4.0
Applying all injections
type family UnProd (h :: (k -> *) -> l -> *) :: (k -> *) -> l -> * Source #
Maps a structure containing products to the corresponding sum structure.
Since: 0.2.4.0
class UnProd (Prod h) ~ h => HApInjs h where Source #
A class for applying all injections corresponding to a sum-like structure to a table containing suitable arguments.
hapInjs :: SListIN h xs => Prod h f xs -> [h f xs] Source #
For a given table (product-like structure), produce a list where each element corresponds to the application of an injection function into the corresponding sum-like structure.
Instances:
hapInjs
,apInjs_NP
::SListI
xs =>NP
f xs -> [NS
f xs ]hapInjs
,apInjs_SOP
::SListI2
xss =>POP
f xs -> [SOP
f xss]
Examples:
>>>
hapInjs (I 'x' :* I True :* I 2 :* Nil)
[Z (I 'x'), S (Z (I True)), S (S (Z (I 2)))]
>>>
hapInjs (POP ((I 'x' :* Nil) :* (I True :* I 2 :* Nil) :* Nil)
[SOP (Z (I 'x' :* Nil)), SOP (S (Z (I True :* (I 2 :* Nil))))]
Since: 0.2.4.0
Expanding sums to products
class HExpand h where Source #
A class for expanding sum structures into corresponding product structures, filling in the slots not targeted by the sum with default values.
Since: 0.2.5.0
hexpand :: SListIN (Prod h) xs => (forall x. f x) -> h f xs -> Prod h f xs Source #
Expand a given sum structure into a corresponding product structure by placing the value contained in the sum into the corresponding position in the product, and using the given default value for all other positions.
Instances:
hexpand
,expand_NS
::SListI
xs => (forall x . f x) ->NS
f xs ->NP
f xshexpand
,expand_SOP
::SListI2
xss => (forall x . f x) ->SOP
f xss ->POP
f xss
Examples:
>>>
hexpand Nothing (S (Z (Just 3))) :: NP Maybe '[Char, Int, Bool]
Nothing :* Just 3 :* Nothing :* Nil>>>
hexpand [] (SOP (S (Z ([1,2] :* "xyz" :* Nil)))) :: POP [] '[ '[Bool], '[Int, Char] ]
POP (([] :* Nil) :* ([1,2] :* "xyz" :* Nil) :* Nil)
Since: 0.2.5.0
hcexpand :: AllN (Prod h) c xs => proxy c -> (forall x. c x => f x) -> h f xs -> Prod h f xs Source #
Variant of hexpand
that allows passing a constrained default.
Instances:
hcexpand
,cexpand_NS
::All
c xs => proxy c -> (forall x . c x => f x) ->NS
f xs ->NP
f xshcexpand
,cexpand_SOP
::All2
c xss => proxy c -> (forall x . c x => f x) ->SOP
f xss ->POP
f xss
Examples:
>>>
hcexpand (Proxy :: Proxy Bounded) (I minBound) (S (Z (I 20))) :: NP I '[Bool, Int, Ordering]
I False :* I 20 :* I LT :* Nil>>>
hcexpand (Proxy :: Proxy Num) (I 0) (SOP (S (Z (I 1 :* I 2 :* Nil)))) :: POP I '[ '[Double], '[Int, Int] ]
POP ((I 0.0 :* Nil) :* (I 1 :* I 2 :* Nil) :* Nil)
Since: 0.2.5.0