From dd13fa9da4841d77863446746e2a6d0ce1fc0edd Mon Sep 17 00:00:00 2001
From: Karsten Schmidt <k@postspectacular.com>
Date: Tue, 12 Feb 2019 15:49:31 +0000
Subject: [PATCH] feat(compose): add new functions

- add constantly()
- add delay()
- add delayed()
- add identity()
---
 packages/compose/src/constantly.ts |  4 ++++
 packages/compose/src/delay.ts      | 29 +++++++++++++++++++++++++++++
 packages/compose/src/delayed.ts    |  3 +++
 packages/compose/src/identity.ts   |  1 +
 packages/compose/src/index.ts      |  4 ++++
 5 files changed, 41 insertions(+)
 create mode 100644 packages/compose/src/constantly.ts
 create mode 100644 packages/compose/src/delay.ts
 create mode 100644 packages/compose/src/delayed.ts
 create mode 100644 packages/compose/src/identity.ts

diff --git a/packages/compose/src/constantly.ts b/packages/compose/src/constantly.ts
new file mode 100644
index 0000000000..2f758a5fc7
--- /dev/null
+++ b/packages/compose/src/constantly.ts
@@ -0,0 +1,4 @@
+import { FnAny } from "@thi.ng/api";
+
+export const constantly =
+    <T>(x: T): FnAny<T> => () => x;
diff --git a/packages/compose/src/delay.ts b/packages/compose/src/delay.ts
new file mode 100644
index 0000000000..7b7efc4064
--- /dev/null
+++ b/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;
+    }
+}
diff --git a/packages/compose/src/delayed.ts b/packages/compose/src/delayed.ts
new file mode 100644
index 0000000000..d250ef0f57
--- /dev/null
+++ b/packages/compose/src/delayed.ts
@@ -0,0 +1,3 @@
+export const delayed =
+    <T>(x: T, t: number) =>
+        new Promise((resolve) => setTimeout(() => resolve(x), t));
diff --git a/packages/compose/src/identity.ts b/packages/compose/src/identity.ts
new file mode 100644
index 0000000000..74efbc8cf1
--- /dev/null
+++ b/packages/compose/src/identity.ts
@@ -0,0 +1 @@
+export const identity = <T>(x: T) => x;
diff --git a/packages/compose/src/index.ts b/packages/compose/src/index.ts
index dfddd39435..f9c76d4c74 100644
--- a/packages/compose/src/index.ts
+++ b/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";