Add SequenceBuilder

.gitignore

@@ -36,6 +36,8 @@ jspm_packages
 # Optional REPL history
 .node_repl_history
 
+*.tgz
+
 # ignore the output directory
 dist/
-coverage
+coverage/

.travis.yml

@@ -1,8 +1,8 @@
 language: node_js
 node_js:
   - "node"
+  - "12"
   - "10"
-  - "8"
 script:
   - npm install
   - npm run build

package.json

@@ -1,9 +1,12 @@
 {
   "name": "gensequence",
-  "version": "2.3.0",
+  "version": "3.0.0",
   "description": "Small library to simplify working with Generators and Iterators in Javascript / Typescript",
   "main": "dist/index.js",
   "typings": "dist/index.d.ts",
+  "engines": {
+    "node": ">=10.0.0"
+  },
   "dependencies": {},
   "devDependencies": {
     "@types/jest": "^24.0.23",

src/GenSequence.perf.ts

@@ -1,4 +1,5 @@
 import * as GS from './GenSequence';
+import {builder} from '.';
 
 describe('Performance Test', () => {
     jest.setTimeout(100000);
@@ -91,6 +92,31 @@ describe('Performance Test', () => {
         assertExpectedRatio('filter slice filter reduce (1000)', rBase, rExp, 2, 3);
     });
 
+    test('builder filter slice filter reduce (1000)', () => {
+        const getValues = () => range(0, 1000);
+        const fnBase = () => {
+            return [...getValues()]
+                .filter(a => !!(a & 1))
+                .slice(100)
+                .slice(0,500)
+                .filter(a => !!(a & 2))
+                .reduce((a, b) => a + b);
+        };
+
+        const fnExp = () => builder
+                .filter<number>(a => !!(a & 1))
+                .skip(100)
+                .take(500)
+                .filter(a => !!(a & 2))
+                .build(getValues())
+                .reduce((a, b) => a + b);
+        const rBase = measure(fnBase, 1000);
+        const rExp = measure(fnExp, 1000);
+
+        expect(rExp.result).toBe(rBase.result);
+        assertExpectedRatio('builder filter slice filter reduce (1000)', rBase, rExp, 2, 3);
+    });
+
     test('filter slice filter first (1000)', () => {
         const getValues = () => range(0, 1000);
         const fnBase = () => {

src/ImplSequence.ts

@@ -1,9 +1,7 @@
-import { Sequence, GenIterable, Maybe } from './util/types';
+import { Sequence, GenIterable, Maybe, LazyIterable, ChainFunction } from './util/types';
 import { filter, skip, take, concat, concatMap, combine, map, scan, all, any, count, first, forEach, max, min, reduce } from './operators';
 import { toIterableIterator } from './util/util';
 
-type LazyIterable<T> = (() => GenIterable<T>) | GenIterable<T>;
-
 export class ImplSequence<T> implements Sequence<T> {
     private _iterator: Maybe<Iterator<T>>;
 
@@ -73,6 +71,10 @@ export class ImplSequence<T> implements Sequence<T> {
         return this.chain(scan(fnReduce, initValue));
     }
 
+    pipe<U>(fn: ChainFunction<T, U>): ImplSequence<U> {
+        return this.chain(fn);
+    }
+
     // Reducers
     all(fnFilter: (t: T) => boolean): boolean {
         return all(fnFilter)(this.iter);

src/ImplSequenceBuilder.test.ts

@@ -0,0 +1,94 @@
+import { ImplSequenceBuilder } from './ImplSequenceBuilder';
+import { map } from './operators';
+import { scanMap } from './operators/operatorsBase';
+import { builder } from './builder';
+
+describe('Verify ImplSequenceBuilder', () => {
+    function getBuilder() {
+        return builder.map((a: number) => a);
+    }
+
+    test('Test empty builder', () => {
+        const a = [1, 2, 3];
+        const b = new ImplSequenceBuilder();
+        const i = b.build(a);
+        expect([...i]).toEqual(a);
+    });
+
+    test('Test empty builder', () => {
+        const a = [1, 2, 3];
+        const b = getBuilder();
+        const i = b.build(a);
+        expect([...i]).toEqual(a);
+    });
+
+    test('Test map', () => {
+        const fn = (a: number) => a * 2;
+        const a = [1, 2, 3];
+        const b = getBuilder().map(fn);
+        const i = b.build(a);
+        expect([...i]).toEqual(a.map(fn));
+    });
+
+    test('Test pipe', () => {
+        const fn = (a: number) => a * 2;
+        const a = [1, 2, 3];
+        const b = getBuilder().pipe(map(fn));
+        const i = b.build(a);
+        expect([...i]).toEqual(a.map(fn));
+    });
+
+    test('Test filter', () => {
+        const fn = (a: number) => !!(a % 2);
+        const a = [1, 2, 3, 4];
+        const b = getBuilder().filter(fn);
+        const i = b.build(a);
+        expect([...i]).toEqual(a.filter(fn));
+    });
+
+    test('Test skip', () => {
+        const a = [1, 2, 3];
+        const b = getBuilder().skip(2);
+        const i = b.build(a);
+        expect([...i]).toEqual(a.slice(2));
+    });
+
+    test('Test take', () => {
+        const a = [1, 2, 3];
+        const b = getBuilder().take(2);
+        const i = b.build(a);
+        expect([...i]).toEqual(a.slice(0, 2));
+    });
+
+    test('Test concat', () => {
+        const a = [1, 2, 3];
+        const c = [6, 7, 8];
+        const b = getBuilder().concat(c);
+        const i = b.build(a);
+        expect([...i]).toEqual(a.concat(c));
+    });
+
+    test('Test concatMap', () => {
+        const fn = (a: number) => [a];
+        const a = [1, 2, 3];
+        const b = getBuilder().concatMap(fn);
+        const i = b.build(a);
+        expect([...i]).toEqual(a);
+    });
+
+    test('Test scan', () => {
+        const fn = (acc: number, cur: number) => acc + cur;
+        const a = [1, 2, 3];
+        const b = getBuilder().scan(fn, 0);
+        const i = b.build(a);
+        expect([...i]).toEqual(a.map(scanMap(fn, 0)));
+    });
+
+    test('Test combine', () => {
+        const fn = (a: number, b: number | undefined) => a + (b ?? 0);
+        const a = [1, 2, 3];
+        const b = getBuilder().combine(fn, a);
+        const i = b.build(a);
+        expect([...i]).toEqual(a.map(a => a * 2));
+    });
+});

src/ImplSequenceBuilder.ts

@@ -0,0 +1,57 @@
+import { SequenceBuilder, ChainFunction, LazyIterable, Sequence } from './util/types';
+import { pipe, filter, skip, take, concat, concatMap, combine, map, scan } from './operators';
+import { ImplSequence } from './ImplSequence';
+
+export class ImplSequenceBuilder<S, T = S> implements SequenceBuilder<S, T> {
+    private operators: ChainFunction<S, T>[] = [];
+
+    constructor(operators: ChainFunction<S, T>[] = []) {
+        this.operators = operators;
+    }
+
+    build(i: LazyIterable<S>): Sequence<T> {
+        return new ImplSequence(i).pipe(pipe.apply<unknown, any, ChainFunction<S, T>>(null, this.operators));
+    }
+
+    pipe<U>(fn: ChainFunction<T, U>): SequenceBuilder<S, U> {
+        return new ImplSequenceBuilder<S, U>([...this.operators, fn] as any[]);
+    }
+
+    //// Filters
+    /** keep values where the fnFilter(t) returns true */
+    filter(fnFilter: (t: T) => boolean): SequenceBuilder<S, T> {
+        return this.pipe(filter(fnFilter));
+    }
+
+    skip(n: number): SequenceBuilder<S, T> {
+        return this.pipe(skip(n));
+    }
+
+    take(n: number): SequenceBuilder<S, T> {
+        return this.pipe(take(n));
+    }
+
+    //// Extenders
+    concat(j: Iterable<T>): SequenceBuilder<S, T> {
+        return this.pipe(concat(j));
+    }
+
+    concatMap<U>(fn: (t: T) => Iterable<U>): SequenceBuilder<S, U> {
+        return this.pipe(concatMap(fn));
+    }
+
+    //// Mappers
+    combine<U, V>(fn: (t: T, u?: U) => V, j: Iterable<U>): SequenceBuilder<S, V> {
+        return this.pipe(combine(fn, j));
+    }
+
+    /** map values from type T to type U */
+    map<U>(fnMap: (t: T) => U): SequenceBuilder<S, U> {
+        return this.pipe(map(fnMap));
+    }
+
+    scan(fnReduce: (previousValue: T, currentValue: T, currentIndex: number) => T, initialValue?: T): SequenceBuilder<S, T>;
+    scan<U>(fnReduce: (previousValue: U, currentValue: T, currentIndex: number) => U, initialValue: U): SequenceBuilder<S, U> {
+        return this.pipe(scan(fnReduce, initialValue));
+    }
+}

src/builder.test.ts

@@ -0,0 +1,76 @@
+import { builder } from './builder';
+import { map } from './operators';
+import { scanMap } from './operators/operatorsBase';
+// import { genSequence } from '.';
+
+describe('Verify builder', () => {
+    test('Test map', () => {
+        const fn = (a: number) => a * 2;
+        const a = [1, 2, 3];
+        const b = builder.map(fn);
+        const i = b.build(a);
+        expect([...i]).toEqual(a.map(fn));
+    });
+
+    test('Test pipe', () => {
+        const fn = (a: number) => a * 2;
+        const a = [1, 2, 3];
+        const b = builder.pipe(map(fn));
+        const i = b.build(a);
+        expect([...i]).toEqual(a.map(fn));
+    });
+
+    test('Test filter', () => {
+        const fn = (a: number) => !!(a % 2);
+        const a = [1, 2, 3, 4];
+        const b = builder.filter(fn);
+        const i = b.build(a);
+        expect([...i]).toEqual(a.filter(fn));
+    });
+
+    test('Test skip', () => {
+        const a = [1, 2, 3];
+        const b = builder.skip(2);
+        const i = b.build(a);
+        expect([...i]).toEqual(a.slice(2));
+    });
+
+    test('Test take', () => {
+        const a = [1, 2, 3];
+        const b = builder.take(2);
+        const i = b.build(a);
+        expect([...i]).toEqual(a.slice(0, 2));
+    });
+
+    test('Test concat', () => {
+        const a = [1, 2, 3];
+        const c = [6, 7, 8];
+        const b = builder.concat(c);
+        const i = b.build(a);
+        expect([...i]).toEqual(a.concat(c));
+    });
+
+    test('Test concatMap', () => {
+        const fn = (a: number) => [a];
+        const a = [1, 2, 3];
+        const b = builder.concatMap(fn);
+        const i = b.build(a);
+        expect([...i]).toEqual(a);
+    });
+
+    test('Test scan', () => {
+        const fn = (acc: number, cur: number) => acc + cur;
+        const a = [1, 2, 3];
+        const b = builder.scan(fn, 0);
+        const i = b.build(a);
+        expect([...i]).toEqual(a.map(scanMap(fn, 0)));
+    });
+
+    test('Test combine', () => {
+        const fn = (a: number, b: number | undefined) => a + (b ?? 0);
+        const a = [1, 2, 3];
+        const b = builder.combine(fn, a);
+        const i = b.build(a);
+        expect([...i]).toEqual(a.map(a => a * 2));
+    });
+});

src/builder.ts

@@ -0,0 +1,51 @@
+import { ChainFunction, SequenceBuilder } from './util/types';
+import { ImplSequenceBuilder } from './ImplSequenceBuilder';
+import { filter, skip, take, concat, concatMap, combine, map, scan } from './operators';
+
+
+function makeBuilder<T, U = T>(fn: ChainFunction<T, U>): SequenceBuilder<T, U> {
+    return new ImplSequenceBuilder([fn]);
+}
+
+export const builder = Object.freeze({
+    pipe: <T, U>(fn: ChainFunction<T, U>) => {
+        return makeBuilder(fn);
+    },
+
+    //// Filters
+    /** keep values where the fnFilter(t) returns true */
+    filter: <T>(fnFilter: (t: T) => boolean) => {
+        return makeBuilder(filter(fnFilter));
+    },
+
+    skip: <T>(n: number) => {
+        return makeBuilder<T>(skip(n));
+    },
+
+    take: <T>(n: number) => {
+        return makeBuilder<T>(take(n));
+    },
+
+    //// Extenders
+    concat: <T>(j: Iterable<T>) => {
+        return makeBuilder(concat(j));
+    },
+
+    concatMap: <T, U>(fn: (t: T) => Iterable<U>) => {
+        return makeBuilder(concatMap(fn));
+    },
+
+    //// Mappers
+    combine: <T, U, V>(fn: (t: T, u?: U) => V, j: Iterable<U>) => {
+        return makeBuilder(combine(fn, j));
+    },
+
+    /** map values from type T to type U */
+    map: <T, U>(fnMap: (t: T) => U) => {
+        return makeBuilder(map(fnMap));
+    },
+
+    scan: <T, U>(fnReduce: (previousValue: U, currentValue: T, currentIndex: number) => U, initialValue: U) => {
+        return makeBuilder(scan(fnReduce, initialValue));
+    },
+});

src/index.ts

@@ -1,2 +1,3 @@
 export * from './GenSequence';
-export { Sequence } from './util/types';
+export { Sequence, LazyIterable, IterableLike, SequenceBuilder } from './util/types';
+export * from './builder';