feat(compose): add new functions

- add constantly()
- add delay()
- add delayed()
- add identity()

packages/compose/src/constantly.ts

@@ -0,0 +1,4 @@
+import { FnAny } from "@thi.ng/api";
+
+export const constantly =
+    <T>(x: T): FnAny<T> => () => x;

packages/compose/src/delay.ts

@@ -0,0 +1,29 @@
+import { IDeref } from "@thi.ng/api";
+
+export const delay =
+    <T>(body: () => T) => new Delay<T>(body);
+
+export class Delay<T> implements
+    IDeref<T> {
+
+    value: T;
+    protected body: () => T;
+    protected realized: boolean;
+
+    constructor(body: () => T) {
+        this.body = body;
+        this.realized = false;
+    }
+
+    deref() {
+        if (!this.realized) {
+            this.value = this.body();
+            this.realized = true;
+        }
+        return this.value;
+    }
+
+    isRealized() {
+        return this.realized;
+    }
+}

packages/compose/src/delayed.ts

@@ -0,0 +1,3 @@
+export const delayed =
+    <T>(x: T, t: number) =>
+        new Promise((resolve) => setTimeout(() => resolve(x), t));

packages/compose/src/identity.ts

@@ -0,0 +1 @@
+export const identity = <T>(x: T) => x;

packages/compose/src/index.ts

@@ -1,4 +1,8 @@
 export * from "./comp";
+export * from "./constantly";
+export * from "./delay";
+export * from "./delayed";
+export * from "./identity";
 export * from "./juxt";
 export * from "./partial";
 export * from "./thread-first";