feat(compose): add partial(), update readme

packages/compose/README.md

@@ -22,9 +22,10 @@ This project is part of the
 
 Functional composition helpers:
 
-- [comp(...)](https://github.com/thi-ng/umbrella/tree/master/packages/compose/src/comp.ts)
-- [compI(...)](https://github.com/thi-ng/umbrella/tree/master/packages/compose/src/comp.ts)
-- [juxt(...)](https://github.com/thi-ng/umbrella/tree/master/packages/compose/src/juxt.ts)
+- [comp()](https://github.com/thi-ng/umbrella/tree/master/packages/compose/src/comp.ts)
+- [compI()](https://github.com/thi-ng/umbrella/tree/master/packages/compose/src/comp.ts)
+- [juxt()](https://github.com/thi-ng/umbrella/tree/master/packages/compose/src/juxt.ts)
+- [partial()](https://github.com/thi-ng/umbrella/tree/master/packages/compose/src/partial.ts)
 
 ## Installation
 

packages/compose/src/index.ts

@@ -1,2 +1,3 @@
 export * from "./comp";
 export * from "./juxt";
+export * from "./partial";

packages/compose/src/partial.ts

@@ -0,0 +1,35 @@
+import { illegalArgs } from "@thi.ng/errors/illegal-arguments";
+
+export function partial<A, T>(fn: (a: A, ...args: any[]) => T, a: A): (...args: any[]) => T;
+export function partial<A, B, T>(fn: (a: A, b: B, ...args: any[]) => T, a: A, b: B): (...args: any[]) => T;
+export function partial<A, B, C, T>(fn: (a: A, b: B, c: C, ...args: any[]) => T, a: A, b: B, c: C): (...args: any[]) => T;
+export function partial<A, B, C, D, T>(fn: (a: A, b: B, c: C, d: D, ...args: any[]) => T, a: A, b: B, c: C, d: D): (...args: any[]) => T;
+export function partial<A, B, C, D, E, T>(fn: (a: A, b: B, c: C, d: D, e: E, ...args: any[]) => T, a: A, b: B, c: C, d: D, e: E): (...args: any[]) => T;
+export function partial<A, B, C, D, E, F, T>(fn: (a: A, b: B, c: C, d: D, e: E, f: F, ...args: any[]) => T, a: A, b: B, c: C, d: D, e: E, f: F): (...args: any[]) => T;
+export function partial<A, B, C, D, E, F, G, T>(fn: (a: A, b: B, c: C, d: D, e: E, f: F, g: G, ...args: any[]) => T, a: A, b: B, c: C, d: D, e: E, f: F, g: G): (...args: any[]) => T;
+export function partial<A, B, C, D, E, F, G, H, T>(fn: (a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, ...args: any[]) => T, a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H): (...args: any[]) => T;
+export function partial(fn, ...args: any[]) {
+    let [a, b, c, d, e, f, g, h] = args;
+    switch (args.length) {
+        case 1:
+            return (...xs: any[]) => fn(a, ...xs);
+        case 2:
+            return (...xs: any[]) => fn(a, b, ...xs);
+        case 3:
+            return (...xs: any[]) => fn(a, b, c, ...xs);
+        case 4:
+            return (...xs: any[]) => fn(a, b, c, d, ...xs);
+        case 5:
+            return (...xs: any[]) => fn(a, b, c, d, e, ...xs);
+        case 6:
+            return (...xs: any[]) => fn(a, b, c, d, e, f, ...xs);
+        case 7:
+            return (...xs: any[]) => fn(a, b, c, d, e, f, g, ...xs);
+        case 8:
+            return (...xs: any[]) => fn(a, b, c, d, e, f, g, h, ...xs);
+        default:
+            illegalArgs();
+    }
+}
+
+export const foo = partial((a: string, b: number) => a + b, "a");