feat: Enforce Functor

MikuroXina · Aug 1, 2022 · 72ba4e8 · 72ba4e8
1 parent 45c12de
commit 72ba4e8
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Showing 2 changed files with 28 additions and 0 deletions.
diff --git a/src/hkt.ts b/src/hkt.ts
@@ -1,3 +1,8 @@
+export interface Hkt<Symbol extends symbol, A> {
+    _symbol: Symbol;
+    _args: A;
+}
+
 export interface HktDictA1<A1> {}
 export interface HktDictA2<A1, A2> extends HktDictA1<A1> {}
 export interface HktDictA3<A1, A2, A3> extends HktDictA2<A1, A2> {}

diff --git a/src/type-class/functor.ts b/src/type-class/functor.ts
@@ -1,4 +1,5 @@
 import type {
+    Hkt,
     HktA1,
     HktA2,
     HktA3,
@@ -9,6 +10,9 @@ import type {
     HktDictA4,
 } from "../hkt";
 
+export interface Functor<F extends symbol> {
+    map<T, U>(fn: (t: T) => U): (t: Hkt<F, T>) => Hkt<F, U>;
+}
 export interface Functor1<A extends HktA1> {
     map<T1, U1>(fn: (t: T1) => U1): (t: HktDictA1<T1>[A]) => HktDictA1<U1>[A];
 }
@@ -25,3 +29,22 @@ export interface Functor4<A extends HktA4> {
         fn: (t: T1) => U1,
     ): (t: HktDictA4<T1, T2, T3, T4>[A]) => HktDictA4<U1, T2, T3, T4>[A];
 }
+
+export const map =
+    <SymbolA extends symbol, SymbolB extends symbol>(
+        funcA: Functor<SymbolA>,
+        funcB: Functor<SymbolB>,
+    ) =>
+    <T, U>(f: (t: T) => U) =>
+    (funcT: Hkt<SymbolA, Hkt<SymbolB, T>>) =>
+        funcA.map(funcB.map(f))(funcT);
+
+export const flap =
+    <Symbol extends symbol>(func: Functor<Symbol>) =>
+    <T, U>(t: T) =>
+        func.map((f: (t: T) => U) => f(t));
+
+export const bindTo =
+    <Symbol extends symbol>(func: Functor<Symbol>) =>
+    <N extends keyof any>(name: N) =>
+        func.map(<T>(a: T) => ({ [name]: a } as Record<N, T>));