From 86d89f89f904c8dd7bd70f5f596c78d63560a82f Mon Sep 17 00:00:00 2001
From: Alexander Nozik <altavir@users.noreply.github.com>
Date: Sun, 10 Apr 2022 10:29:44 +0300
Subject: [PATCH] Update
 kmath-histograms/src/commonMain/kotlin/space/kscience/kmath/histogram/IndexedHistogramGroup.kt

Co-authored-by: Iaroslav Postovalov <38042667+CommanderTvis@users.noreply.github.com>
---
 .../space/kscience/kmath/histogram/IndexedHistogramGroup.kt  | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kmath-histograms/src/commonMain/kotlin/space/kscience/kmath/histogram/IndexedHistogramGroup.kt b/kmath-histograms/src/commonMain/kotlin/space/kscience/kmath/histogram/IndexedHistogramGroup.kt
index 9749f8403..b1d317a15 100644
--- a/kmath-histograms/src/commonMain/kotlin/space/kscience/kmath/histogram/IndexedHistogramGroup.kt
+++ b/kmath-histograms/src/commonMain/kotlin/space/kscience/kmath/histogram/IndexedHistogramGroup.kt
@@ -68,8 +68,9 @@ public interface IndexedHistogramGroup<T : Comparable<T>, V : Any> : Group<Index
     public fun produce(builder: HistogramBuilder<T, V>.() -> Unit): IndexedHistogram<T, V>
 
     override fun add(left: IndexedHistogram<T, V>, right: IndexedHistogram<T, V>): IndexedHistogram<T, V> {
-        require(left.histogramSpace == this) { "Can't operate on a histogram produced by external space" }
-        require(right.histogramSpace == this) { "Can't operate on a histogram produced by external space" }
+        require(left.histogramSpace == this && right.histogramSpace == this) {
+            "A histogram belonging to a different group cannot be operated."
+        }
         return IndexedHistogram(this, histogramValueAlgebra { left.values + right.values })
     }