From 018ee3203be88e30a97346fad5f2fb9e48c7c9a9 Mon Sep 17 00:00:00 2001
From: Mariia Mykhailova <mamykhai@microsoft.com>
Date: Thu, 10 Mar 2022 10:31:31 -0800
Subject: [PATCH] Chunks: Add check that chunk size is positive

Fixes #538.
---
 Standard/src/Arrays/Arrays.qs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Standard/src/Arrays/Arrays.qs b/Standard/src/Arrays/Arrays.qs
index 23d4d4e5668..7506b9efcbd 100644
--- a/Standard/src/Arrays/Arrays.qs
+++ b/Standard/src/Arrays/Arrays.qs
@@ -283,7 +283,7 @@ namespace Microsoft.Quantum.Arrays {
     ///
     /// # Input
     /// ## nElements
-    /// The length of each chunk.
+    /// The length of each chunk. Must be positive.
     /// ## arr
     /// The array to be split.
     ///
@@ -294,6 +294,7 @@ namespace Microsoft.Quantum.Arrays {
     /// Note that the last element of the output may be shorter
     /// than `nElements` if `Length(arr)` is not divisible by `nElements`.
     function Chunks<'T>(nElements : Int, arr : 'T[]) : 'T[][] {
+        Fact(nElements > 0, "nElements must be positive");
         mutable output = [];
         mutable remaining = arr;
         while (not IsEmpty(remaining)) {