draft: FnAsyncEither

examples/fn/fn_async_either.ts

@@ -0,0 +1,41 @@
+import * as F from "../../fn.ts";
+import * as FAE from "../../fn_async_either.ts";
+
+const add1 = await F.pipe(
+  FAE.ask<number>(),
+  FAE.map((n) => n + 1),
+  FAE.match(() => 0, F.identity),
+);
+
+add1(2).then((n) => console.log(n)); // 3
+
+const failable = F.pipe(
+  FAE.tryCatch(
+    (n: number) => n % 2 === 0 ? Promise.resolve("even") : Promise.reject("odd"),
+    () => "fail: odd",
+  ),
+  FAE.match(() => "fail: even", F.identity),
+);
+
+failable(1).then((n) => console.log(n)); // odd;
+
+const askN = FAE.ask<number>();
+
+const divide = ([dividend, divisor]: [number, number]) => dividend / divisor;
+const onError = (error: unknown, [[dividend, divisor]]: [[number, number]]) =>
+  `Error dividing ${dividend} by ${divisor}`;
+const safeDivide = FAE.tryCatch(divide, onError);
+
+safeDivide([10, 2]); // returns Right(5)
+safeDivide([10, 0]); // returns Left("Error dividing 10 by 0")
+
+const _fetch = FAE.tryCatch(
+  fetch,
+  (error, args) => ({ message: "Fetch Error", error, args }),
+);
+
+const t1 = await _fetch("blah")();
+const t2 = await _fetch("https://deno.land/")();
+
+const computation = FAE.left<number, number, number>(1);
+const result = await computation()();