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https://github.com/IBM/fp-go.git
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94 lines
2.4 KiB
Go
94 lines
2.4 KiB
Go
package record
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import (
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F "github.com/ibm/fp-go/function"
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)
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// createEmpty creates a new empty, read-write map
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// this is different to Empty which creates a new read-only empty map
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func createEmpty[N ~map[K]A, K comparable, A any]() N {
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return make(N)
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}
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// inserts the key/value pair into a read-write map for performance
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// order of parameters is adjusted to be curryable
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func addKey[N ~map[K]A, K comparable, A any](key K, m N, value A) N {
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m[key] = value
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return m
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}
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/*
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*
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We need to pass the members of the applicative explicitly, because golang does neither support higher kinded types nor template methods on structs or interfaces
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HKTRB = HKT<MB>
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HKTA = HKT<A>
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HKTB = HKT<B>
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HKTAB = HKT<func(A)B>
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*/
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func traverseWithIndex[MA ~map[K]A, MB ~map[K]B, K comparable, A, B, HKTB, HKTAB, HKTRB any](
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_of func(MB) HKTRB,
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_map func(HKTRB, func(MB) func(B) MB) HKTAB,
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_ap func(HKTAB, HKTB) HKTRB,
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ta MA, f func(K, A) HKTB) HKTRB {
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// this function inserts a value into a map with a given key
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cb := F.Curry3(addKey[MB, K, B])
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return ReduceWithIndex(ta, func(k K, r HKTRB, a A) HKTRB {
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return _ap(
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_map(r, cb(k)),
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f(k, a),
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)
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}, _of(createEmpty[MB]()))
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}
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func MonadTraverse[MA ~map[K]A, MB ~map[K]B, K comparable, A, B, HKTB, HKTAB, HKTRB any](
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_of func(MB) HKTRB,
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_map func(HKTRB, func(MB) func(B) MB) HKTAB,
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_ap func(HKTAB, HKTB) HKTRB,
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r MA, f func(A) HKTB) HKTRB {
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return traverseWithIndex(_of, _map, _ap, r, F.Ignore1st[K](f))
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}
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func TraverseWithIndex[MA ~map[K]A, MB ~map[K]B, K comparable, A, B, HKTB, HKTAB, HKTRB any](
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_of func(MB) HKTRB,
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_map func(HKTRB, func(MB) func(B) MB) HKTAB,
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_ap func(HKTAB, HKTB) HKTRB,
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f func(K, A) HKTB) func(MA) HKTRB {
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return func(ma MA) HKTRB {
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return traverseWithIndex(_of, _map, _ap, ma, f)
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}
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}
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// HKTA = HKT<A>
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// HKTB = HKT<B>
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// HKTAB = HKT<func(A)B>
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// HKTRB = HKT<MB>
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func Traverse[MA ~map[K]A, MB ~map[K]B, K comparable, A, B, HKTB, HKTAB, HKTRB any](
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_of func(MB) HKTRB,
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_map func(HKTRB, func(MB) func(B) MB) HKTAB,
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_ap func(HKTAB, HKTB) HKTRB,
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f func(A) HKTB) func(MA) HKTRB {
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return func(ma MA) HKTRB {
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return MonadTraverse(_of, _map, _ap, ma, f)
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}
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}
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// HKTA = HKT[A]
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// HKTAA = HKT[func(A)MA]
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// HKTRA = HKT[MA]
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func Sequence[MA ~map[K]A, MKTA ~map[K]HKTA, K comparable, A, HKTA, HKTAA, HKTRA any](
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_of func(MA) HKTRA,
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_map func(HKTRA, func(MA) func(A) MA) HKTAA,
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_ap func(HKTAA, HKTA) HKTRA,
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ma MKTA) HKTRA {
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return MonadTraverse(_of, _map, _ap, ma, F.Identity[HKTA])
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}
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