src/utils.mjs: Add take() and range()

1 files changed, 40 insertions, 0 deletions

diff --git a/src/utils.mjs b/src/utils.mjs
index 9a600e7..19c8e37 100644
--- a/src/utils.mjs
+++ b/src/utils.mjs
@@ -58,3 +58,43 @@ export const first   = a => a[0];
 export const rest    = a => a.slice(1);
 export const butlast = a => a.slice(a, a.length - 1);
 export const last    = a => a[a.length - 1];
+
+export const take = function*(n, gen) {
+	let i = 0n;
+	for (const x of gen) {
+		if (i >= n) {
+			break;
+		}
+		i++;
+		yield x;
+	}
+};
+
+export const range = function*(x, y, step = 1n) {
+	if (x === undefined) {
+		let i = 0n;
+		while (true) {
+			yield i++;
+		}
+	}
+	const [from, to] = y === undefined ?
+		[0n, x] :
+		[x, y];
+	const fromn = BigInt(from);
+	const ton   = BigInt(to);
+	const stepn = BigInt(step);
+	if (stepn === 0n) {
+		while (true) {
+			yield fromn;
+		}
+	}
+	if (step < 0n) {
+		for (let i = fromn; i > ton; i+= stepn) {
+			yield i;
+		}
+	} else {
+		for (let i = fromn; i < ton; i += stepn) {
+			yield i;
+		}
+	}
+};