monads/nothing-monad

TODO.md

@@ -1,4 +1,3 @@
-monads/nothing-monad
 用 generic 函数定义 lift -- 删除 `skipIncompleteInputs`
 monads/supported-monad -- 删除 `maybeUnwrapSupported`
 

src/monads/nothing-monad.ts

@@ -0,0 +1,7 @@
+import { isNothing, nothing } from "../cell/Nothing.js"
+import { defineHandler } from "../generic/index.js"
+import { fmap, join } from "../monad/index.js"
+import { isFunction } from "../utils/isFunction.js"
+
+defineHandler(fmap, [isFunction, isNothing], (f, mx) => nothing)
+defineHandler(join, [isNothing], (mmx) => nothing)

src/utils/isFunction.ts

@@ -0,0 +1,3 @@
+export function isFunction(x: any): x is Function {
+  return typeof x === "function"
+}