briancavalier · June 1, 2016 22:50 · Jun 1, 2016
diff --git a/stream.js b/stream.js
@@ -0,0 +1,90 @@
+function * empty() {}
+
+function * cons (a, stream) {
+  yield a
+  yield * stream
+}
+
+function * concat (xs, ys) {
+  yield * xs
+  yield * ys
+}
+
+function * map (f, stream) {
+  for(const x of stream) {
+    yield f(x)
+  }
+}
+
+function * filter (p, stream) {
+  for(const x of stream) {
+    if(p(x)) {
+      yield x
+    }
+  }
+}
+
+function * take (n, stream) {
+  for(let x of stream) {
+    if(n-- === 0) {
+      return
+    }
+    yield x
+  }
+}
+
+function * skip (n, stream) {
+  for (let x of stream) {
+    if(--n === 0) {
+      break
+    }
+  }
+  yield * stream
+}
+
+function * ap (fs, xs) {
+  yield * zipWith(apply, fs, xs)
+}
+
+const apply = (f, x) => f(x)
+
+function * chain (f, stream) {
+  for(let x of stream) {
+    yield * f(x)
+  }
+}
+
+function * zipWith (f, xs, ys) {
+  let x = xs.next()
+  let y = ys.next()
+  while(!x.done && !y.done) {
+    yield f(x.value, y.value)
+    x = xs.next()
+    y = ys.next()
+  }
+}
+
+function * iterate (f, a) {
+  yield a
+  for(;;) {
+    a = f(a)
+    yield a
+  }
+}
+
+function * unfold (f, a) {
+  let [x, y] = f(a)
+  for(;;) {
+    yield x
+    [x, y] = f(y)
+  }
+}
+
+function * integers () {
+  yield * iterate(x => x + 1, 0)
+}
+
+const stream = chain(x => take(3, integers()), take(10, integers()))
+for(const y of stream) {
+  console.log(y)
+}