More support for asynchronous operations

src/ext/infestines.js

@@ -36,3 +36,46 @@ export function isPrimitiveData(x) {
 }
 
 export const iterator = Symbol.iterator
+
+export const thenU = I.Async.chain
+export const then = I.curry(thenU)
+
+export const thenIdentityU = I.IdentityAsync.chain
+
+const EMPTY = 'empty'
+const CONCAT = 'concat'
+
+export function Monoid(concat, empty) {
+  if (!I.isInstanceOfU(Monoid, this)) return I.freeze(new Monoid(concat, empty))
+  this[CONCAT] = concat
+  this[EMPTY] = empty
+}
+
+export const MonoidWith = (concat, empty) => Monoid(concat, I.always(empty))
+
+export const MonoidAsyncOf = m => {
+  const concat = m[CONCAT]
+  return Monoid(
+    (l, r) =>
+      I.isThenable(l)
+        ? thenU(
+            l => (I.isThenable(r) ? thenU(r => concat(l, r), r) : concat(l, r)),
+            l
+          )
+        : I.isThenable(r)
+        ? thenU(r => concat(l, r), r)
+        : concat(l, r),
+    m[EMPTY]
+  )
+}
+
+export const ProductMonoid = MonoidWith(multiplyU, 1)
+
+export const SumMonoid = MonoidWith(addU, 0)
+
+export const ConstantWith = (ap, empty) =>
+  I.Applicative(I.sndU, I.always(empty), ap)
+
+export const ConstantOf = m => ConstantWith(m[CONCAT], m[EMPTY]())
+
+export const ConstantAsyncOf = I.pipe2U(MonoidAsyncOf, ConstantOf)