Document and test NaN propagation of maxOf/minOf

Also simplify minOf/maxOf implementations

#KT-38708

libraries/stdlib/common/src/generated/_Collections.kt

@@ -1797,6 +1797,8 @@ public inline fun <T, R : Comparable<R>> Iterable<T>.maxBy(selector: (T) -> R):
  * Returns the largest value among all values produced by [selector] function
  * applied to each element in the collection.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the collection is empty.
  */
 @SinceKotlin("1.4")
@@ -1807,13 +1809,9 @@ public inline fun <T> Iterable<T>.maxOf(selector: (T) -> Double): Double {
     val iterator = iterator()
     if (!iterator.hasNext()) throw NoSuchElementException()
     var maxValue = selector(iterator.next())
-    if (maxValue.isNaN()) return maxValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        maxValue = maxOf(maxValue, v)
-        if (maxValue < v) {
-            maxValue = v
-        }
     }
     return maxValue
 }
@@ -1822,6 +1820,8 @@ public inline fun <T> Iterable<T>.maxOf(selector: (T) -> Double): Double {
  * Returns the largest value among all values produced by [selector] function
  * applied to each element in the collection.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the collection is empty.
  */
 @SinceKotlin("1.4")
@@ -1832,13 +1832,9 @@ public inline fun <T> Iterable<T>.maxOf(selector: (T) -> Float): Float {
     val iterator = iterator()
     if (!iterator.hasNext()) throw NoSuchElementException()
     var maxValue = selector(iterator.next())
-    if (maxValue.isNaN()) return maxValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        maxValue = maxOf(maxValue, v)
-        if (maxValue < v) {
-            maxValue = v
-        }
     }
     return maxValue
 }
@@ -1859,7 +1855,6 @@ public inline fun <T, R : Comparable<R>> Iterable<T>.maxOf(selector: (T) -> R):
     var maxValue = selector(iterator.next())
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        
         if (maxValue < v) {
             maxValue = v
         }
@@ -1870,6 +1865,8 @@ public inline fun <T, R : Comparable<R>> Iterable<T>.maxOf(selector: (T) -> R):
 /**
  * Returns the largest value among all values produced by [selector] function
  * applied to each element in the collection or `null` if there are no elements.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  */
 @SinceKotlin("1.4")
 @OptIn(kotlin.experimental.ExperimentalTypeInference::class)
@@ -1879,13 +1876,9 @@ public inline fun <T> Iterable<T>.maxOfOrNull(selector: (T) -> Double): Double?
     val iterator = iterator()
     if (!iterator.hasNext()) return null
     var maxValue = selector(iterator.next())
-    if (maxValue.isNaN()) return maxValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        maxValue = maxOf(maxValue, v)
-        if (maxValue < v) {
-            maxValue = v
-        }
     }
     return maxValue
 }
@@ -1893,6 +1886,8 @@ public inline fun <T> Iterable<T>.maxOfOrNull(selector: (T) -> Double): Double?
 /**
  * Returns the largest value among all values produced by [selector] function
  * applied to each element in the collection or `null` if there are no elements.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  */
 @SinceKotlin("1.4")
 @OptIn(kotlin.experimental.ExperimentalTypeInference::class)
@@ -1902,13 +1897,9 @@ public inline fun <T> Iterable<T>.maxOfOrNull(selector: (T) -> Float): Float? {
     val iterator = iterator()
     if (!iterator.hasNext()) return null
     var maxValue = selector(iterator.next())
-    if (maxValue.isNaN()) return maxValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        maxValue = maxOf(maxValue, v)
-        if (maxValue < v) {
-            maxValue = v
-        }
     }
     return maxValue
 }
@@ -1927,7 +1918,6 @@ public inline fun <T, R : Comparable<R>> Iterable<T>.maxOfOrNull(selector: (T) -
     var maxValue = selector(iterator.next())
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        
         if (maxValue < v) {
             maxValue = v
         }
@@ -2071,6 +2061,8 @@ public inline fun <T, R : Comparable<R>> Iterable<T>.minBy(selector: (T) -> R):
  * Returns the smallest value among all values produced by [selector] function
  * applied to each element in the collection.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the collection is empty.
  */
 @SinceKotlin("1.4")
@@ -2081,13 +2073,9 @@ public inline fun <T> Iterable<T>.minOf(selector: (T) -> Double): Double {
     val iterator = iterator()
     if (!iterator.hasNext()) throw NoSuchElementException()
     var minValue = selector(iterator.next())
-    if (minValue.isNaN()) return minValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        minValue = minOf(minValue, v)
-        if (minValue > v) {
-            minValue = v
-        }
     }
     return minValue
 }
@@ -2096,6 +2084,8 @@ public inline fun <T> Iterable<T>.minOf(selector: (T) -> Double): Double {
  * Returns the smallest value among all values produced by [selector] function
  * applied to each element in the collection.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the collection is empty.
  */
 @SinceKotlin("1.4")
@@ -2106,13 +2096,9 @@ public inline fun <T> Iterable<T>.minOf(selector: (T) -> Float): Float {
     val iterator = iterator()
     if (!iterator.hasNext()) throw NoSuchElementException()
     var minValue = selector(iterator.next())
-    if (minValue.isNaN()) return minValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        minValue = minOf(minValue, v)
-        if (minValue > v) {
-            minValue = v
-        }
     }
     return minValue
 }
@@ -2133,7 +2119,6 @@ public inline fun <T, R : Comparable<R>> Iterable<T>.minOf(selector: (T) -> R):
     var minValue = selector(iterator.next())
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        
         if (minValue > v) {
             minValue = v
         }
@@ -2144,6 +2129,8 @@ public inline fun <T, R : Comparable<R>> Iterable<T>.minOf(selector: (T) -> R):
 /**
  * Returns the smallest value among all values produced by [selector] function
  * applied to each element in the collection or `null` if there are no elements.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  */
 @SinceKotlin("1.4")
 @OptIn(kotlin.experimental.ExperimentalTypeInference::class)
@@ -2153,13 +2140,9 @@ public inline fun <T> Iterable<T>.minOfOrNull(selector: (T) -> Double): Double?
     val iterator = iterator()
     if (!iterator.hasNext()) return null
     var minValue = selector(iterator.next())
-    if (minValue.isNaN()) return minValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        minValue = minOf(minValue, v)
-        if (minValue > v) {
-            minValue = v
-        }
     }
     return minValue
 }
@@ -2167,6 +2150,8 @@ public inline fun <T> Iterable<T>.minOfOrNull(selector: (T) -> Double): Double?
 /**
  * Returns the smallest value among all values produced by [selector] function
  * applied to each element in the collection or `null` if there are no elements.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  */
 @SinceKotlin("1.4")
 @OptIn(kotlin.experimental.ExperimentalTypeInference::class)
@@ -2176,13 +2161,9 @@ public inline fun <T> Iterable<T>.minOfOrNull(selector: (T) -> Float): Float? {
     val iterator = iterator()
     if (!iterator.hasNext()) return null
     var minValue = selector(iterator.next())
-    if (minValue.isNaN()) return minValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        minValue = minOf(minValue, v)
-        if (minValue > v) {
-            minValue = v
-        }
     }
     return minValue
 }
@@ -2201,7 +2182,6 @@ public inline fun <T, R : Comparable<R>> Iterable<T>.minOfOrNull(selector: (T) -
     var minValue = selector(iterator.next())
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        
         if (minValue > v) {
             minValue = v
         }

libraries/stdlib/common/src/generated/_Maps.kt

@@ -193,6 +193,8 @@ public inline fun <K, V, R : Comparable<R>> Map<out K, V>.maxBy(selector: (Map.E
  * Returns the largest value among all values produced by [selector] function
  * applied to each entry in the map.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the map is empty.
  */
 @SinceKotlin("1.4")
@@ -207,6 +209,8 @@ public inline fun <K, V> Map<out K, V>.maxOf(selector: (Map.Entry<K, V>) -> Doub
  * Returns the largest value among all values produced by [selector] function
  * applied to each entry in the map.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the map is empty.
  */
 @SinceKotlin("1.4")
@@ -234,6 +238,8 @@ public inline fun <K, V, R : Comparable<R>> Map<out K, V>.maxOf(selector: (Map.E
 /**
  * Returns the largest value among all values produced by [selector] function
  * applied to each entry in the map or `null` if there are no entries.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  */
 @SinceKotlin("1.4")
 @OptIn(kotlin.experimental.ExperimentalTypeInference::class)
@@ -246,6 +252,8 @@ public inline fun <K, V> Map<out K, V>.maxOfOrNull(selector: (Map.Entry<K, V>) -
 /**
  * Returns the largest value among all values produced by [selector] function
  * applied to each entry in the map or `null` if there are no entries.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  */
 @SinceKotlin("1.4")
 @OptIn(kotlin.experimental.ExperimentalTypeInference::class)
@@ -314,6 +322,8 @@ public inline fun <K, V, R : Comparable<R>> Map<out K, V>.minBy(selector: (Map.E
  * Returns the smallest value among all values produced by [selector] function
  * applied to each entry in the map.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the map is empty.
  */
 @SinceKotlin("1.4")
@@ -328,6 +338,8 @@ public inline fun <K, V> Map<out K, V>.minOf(selector: (Map.Entry<K, V>) -> Doub
  * Returns the smallest value among all values produced by [selector] function
  * applied to each entry in the map.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the map is empty.
  */
 @SinceKotlin("1.4")
@@ -355,6 +367,8 @@ public inline fun <K, V, R : Comparable<R>> Map<out K, V>.minOf(selector: (Map.E
 /**
  * Returns the smallest value among all values produced by [selector] function
  * applied to each entry in the map or `null` if there are no entries.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  */
 @SinceKotlin("1.4")
 @OptIn(kotlin.experimental.ExperimentalTypeInference::class)
@@ -367,6 +381,8 @@ public inline fun <K, V> Map<out K, V>.minOfOrNull(selector: (Map.Entry<K, V>) -
 /**
  * Returns the smallest value among all values produced by [selector] function
  * applied to each entry in the map or `null` if there are no entries.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  */
 @SinceKotlin("1.4")
 @OptIn(kotlin.experimental.ExperimentalTypeInference::class)

libraries/stdlib/common/src/generated/_Sequences.kt

@@ -1252,6 +1252,8 @@ public inline fun <T, R : Comparable<R>> Sequence<T>.maxBy(selector: (T) -> R):
  * Returns the largest value among all values produced by [selector] function
  * applied to each element in the sequence.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the sequence is empty.
  *
  * The operation is _terminal_.
@@ -1264,13 +1266,9 @@ public inline fun <T> Sequence<T>.maxOf(selector: (T) -> Double): Double {
     val iterator = iterator()
     if (!iterator.hasNext()) throw NoSuchElementException()
     var maxValue = selector(iterator.next())
-    if (maxValue.isNaN()) return maxValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        maxValue = maxOf(maxValue, v)
-        if (maxValue < v) {
-            maxValue = v
-        }
     }
     return maxValue
 }
@@ -1279,6 +1277,8 @@ public inline fun <T> Sequence<T>.maxOf(selector: (T) -> Double): Double {
  * Returns the largest value among all values produced by [selector] function
  * applied to each element in the sequence.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the sequence is empty.
  *
  * The operation is _terminal_.
@@ -1291,13 +1291,9 @@ public inline fun <T> Sequence<T>.maxOf(selector: (T) -> Float): Float {
     val iterator = iterator()
     if (!iterator.hasNext()) throw NoSuchElementException()
     var maxValue = selector(iterator.next())
-    if (maxValue.isNaN()) return maxValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        maxValue = maxOf(maxValue, v)
-        if (maxValue < v) {
-            maxValue = v
-        }
     }
     return maxValue
 }
@@ -1320,7 +1316,6 @@ public inline fun <T, R : Comparable<R>> Sequence<T>.maxOf(selector: (T) -> R):
     var maxValue = selector(iterator.next())
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        
         if (maxValue < v) {
             maxValue = v
         }
@@ -1331,6 +1326,8 @@ public inline fun <T, R : Comparable<R>> Sequence<T>.maxOf(selector: (T) -> R):
 /**
  * Returns the largest value among all values produced by [selector] function
  * applied to each element in the sequence or `null` if there are no elements.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  *
  * The operation is _terminal_.
  */
@@ -1342,13 +1339,9 @@ public inline fun <T> Sequence<T>.maxOfOrNull(selector: (T) -> Double): Double?
     val iterator = iterator()
     if (!iterator.hasNext()) return null
     var maxValue = selector(iterator.next())
-    if (maxValue.isNaN()) return maxValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        maxValue = maxOf(maxValue, v)
-        if (maxValue < v) {
-            maxValue = v
-        }
     }
     return maxValue
 }
@@ -1356,6 +1349,8 @@ public inline fun <T> Sequence<T>.maxOfOrNull(selector: (T) -> Double): Double?
 /**
  * Returns the largest value among all values produced by [selector] function
  * applied to each element in the sequence or `null` if there are no elements.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  *
  * The operation is _terminal_.
  */
@@ -1367,13 +1362,9 @@ public inline fun <T> Sequence<T>.maxOfOrNull(selector: (T) -> Float): Float? {
     val iterator = iterator()
     if (!iterator.hasNext()) return null
     var maxValue = selector(iterator.next())
-    if (maxValue.isNaN()) return maxValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        maxValue = maxOf(maxValue, v)
-        if (maxValue < v) {
-            maxValue = v
-        }
     }
     return maxValue
 }
@@ -1394,7 +1385,6 @@ public inline fun <T, R : Comparable<R>> Sequence<T>.maxOfOrNull(selector: (T) -
     var maxValue = selector(iterator.next())
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        
         if (maxValue < v) {
             maxValue = v
         }
@@ -1552,6 +1542,8 @@ public inline fun <T, R : Comparable<R>> Sequence<T>.minBy(selector: (T) -> R):
  * Returns the smallest value among all values produced by [selector] function
  * applied to each element in the sequence.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the sequence is empty.
  *
  * The operation is _terminal_.
@@ -1564,13 +1556,9 @@ public inline fun <T> Sequence<T>.minOf(selector: (T) -> Double): Double {
     val iterator = iterator()
     if (!iterator.hasNext()) throw NoSuchElementException()
     var minValue = selector(iterator.next())
-    if (minValue.isNaN()) return minValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        minValue = minOf(minValue, v)
-        if (minValue > v) {
-            minValue = v
-        }
     }
     return minValue
 }
@@ -1579,6 +1567,8 @@ public inline fun <T> Sequence<T>.minOf(selector: (T) -> Double): Double {
  * Returns the smallest value among all values produced by [selector] function
  * applied to each element in the sequence.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the sequence is empty.
  *
  * The operation is _terminal_.
@@ -1591,13 +1581,9 @@ public inline fun <T> Sequence<T>.minOf(selector: (T) -> Float): Float {
     val iterator = iterator()
     if (!iterator.hasNext()) throw NoSuchElementException()
     var minValue = selector(iterator.next())
-    if (minValue.isNaN()) return minValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        minValue = minOf(minValue, v)
-        if (minValue > v) {
-            minValue = v
-        }
     }
     return minValue
 }
@@ -1620,7 +1606,6 @@ public inline fun <T, R : Comparable<R>> Sequence<T>.minOf(selector: (T) -> R):
     var minValue = selector(iterator.next())
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        
         if (minValue > v) {
             minValue = v
         }
@@ -1631,6 +1616,8 @@ public inline fun <T, R : Comparable<R>> Sequence<T>.minOf(selector: (T) -> R):
 /**
  * Returns the smallest value among all values produced by [selector] function
  * applied to each element in the sequence or `null` if there are no elements.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  *
  * The operation is _terminal_.
  */
@@ -1642,13 +1629,9 @@ public inline fun <T> Sequence<T>.minOfOrNull(selector: (T) -> Double): Double?
     val iterator = iterator()
     if (!iterator.hasNext()) return null
     var minValue = selector(iterator.next())
-    if (minValue.isNaN()) return minValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        minValue = minOf(minValue, v)
-        if (minValue > v) {
-            minValue = v
-        }
     }
     return minValue
 }
@@ -1656,6 +1639,8 @@ public inline fun <T> Sequence<T>.minOfOrNull(selector: (T) -> Double): Double?
 /**
  * Returns the smallest value among all values produced by [selector] function
  * applied to each element in the sequence or `null` if there are no elements.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  *
  * The operation is _terminal_.
  */
@@ -1667,13 +1652,9 @@ public inline fun <T> Sequence<T>.minOfOrNull(selector: (T) -> Float): Float? {
     val iterator = iterator()
     if (!iterator.hasNext()) return null
     var minValue = selector(iterator.next())
-    if (minValue.isNaN()) return minValue
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        if (v.isNaN()) return v
+        minValue = minOf(minValue, v)
-        if (minValue > v) {
-            minValue = v
-        }
     }
     return minValue
 }
@@ -1694,7 +1675,6 @@ public inline fun <T, R : Comparable<R>> Sequence<T>.minOfOrNull(selector: (T) -
     var minValue = selector(iterator.next())
     while (iterator.hasNext()) {
         val v = selector(iterator.next())
-        
         if (minValue > v) {
             minValue = v
         }

libraries/stdlib/common/src/generated/_Strings.kt

@@ -1127,6 +1127,8 @@ public inline fun <R : Comparable<R>> CharSequence.maxBy(selector: (Char) -> R):
  * Returns the largest value among all values produced by [selector] function
  * applied to each character in the char sequence.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the char sequence is empty.
  */
 @SinceKotlin("1.4")
@@ -1136,15 +1138,9 @@ public inline fun <R : Comparable<R>> CharSequence.maxBy(selector: (Char) -> R):
 public inline fun CharSequence.maxOf(selector: (Char) -> Double): Double {
     if (isEmpty()) throw NoSuchElementException()
     var maxValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return maxValue
-    if (maxValue.isNaN()) return maxValue 
     for (i in 1..lastIndex) {
         val v = selector(this[i])
-        if (v.isNaN()) return v
+        maxValue = maxOf(maxValue, v)
-        if (maxValue < v) {
-            maxValue = v
-        }
     }
     return maxValue
 }
@@ -1153,6 +1149,8 @@ public inline fun CharSequence.maxOf(selector: (Char) -> Double): Double {
  * Returns the largest value among all values produced by [selector] function
  * applied to each character in the char sequence.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the char sequence is empty.
  */
 @SinceKotlin("1.4")
@@ -1162,15 +1160,9 @@ public inline fun CharSequence.maxOf(selector: (Char) -> Double): Double {
 public inline fun CharSequence.maxOf(selector: (Char) -> Float): Float {
     if (isEmpty()) throw NoSuchElementException()
     var maxValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return maxValue
-    if (maxValue.isNaN()) return maxValue 
     for (i in 1..lastIndex) {
         val v = selector(this[i])
-        if (v.isNaN()) return v
+        maxValue = maxOf(maxValue, v)
-        if (maxValue < v) {
-            maxValue = v
-        }
     }
     return maxValue
 }
@@ -1188,12 +1180,8 @@ public inline fun CharSequence.maxOf(selector: (Char) -> Float): Float {
 public inline fun <R : Comparable<R>> CharSequence.maxOf(selector: (Char) -> R): R {
     if (isEmpty()) throw NoSuchElementException()
     var maxValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return maxValue
-     
     for (i in 1..lastIndex) {
         val v = selector(this[i])
-        
         if (maxValue < v) {
             maxValue = v
         }
@@ -1204,6 +1192,8 @@ public inline fun <R : Comparable<R>> CharSequence.maxOf(selector: (Char) -> R):
 /**
  * Returns the largest value among all values produced by [selector] function
  * applied to each character in the char sequence or `null` if there are no characters.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  */
 @SinceKotlin("1.4")
 @OptIn(kotlin.experimental.ExperimentalTypeInference::class)
@@ -1212,15 +1202,9 @@ public inline fun <R : Comparable<R>> CharSequence.maxOf(selector: (Char) -> R):
 public inline fun CharSequence.maxOfOrNull(selector: (Char) -> Double): Double? {
     if (isEmpty()) return null
     var maxValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return maxValue
-    if (maxValue.isNaN()) return maxValue 
     for (i in 1..lastIndex) {
         val v = selector(this[i])
-        if (v.isNaN()) return v
+        maxValue = maxOf(maxValue, v)
-        if (maxValue < v) {
-            maxValue = v
-        }
     }
     return maxValue
 }
@@ -1228,6 +1212,8 @@ public inline fun CharSequence.maxOfOrNull(selector: (Char) -> Double): Double?
 /**
  * Returns the largest value among all values produced by [selector] function
  * applied to each character in the char sequence or `null` if there are no characters.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  */
 @SinceKotlin("1.4")
 @OptIn(kotlin.experimental.ExperimentalTypeInference::class)
@@ -1236,15 +1222,9 @@ public inline fun CharSequence.maxOfOrNull(selector: (Char) -> Double): Double?
 public inline fun CharSequence.maxOfOrNull(selector: (Char) -> Float): Float? {
     if (isEmpty()) return null
     var maxValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return maxValue
-    if (maxValue.isNaN()) return maxValue 
     for (i in 1..lastIndex) {
         val v = selector(this[i])
-        if (v.isNaN()) return v
+        maxValue = maxOf(maxValue, v)
-        if (maxValue < v) {
-            maxValue = v
-        }
     }
     return maxValue
 }
@@ -1260,12 +1240,8 @@ public inline fun CharSequence.maxOfOrNull(selector: (Char) -> Float): Float? {
 public inline fun <R : Comparable<R>> CharSequence.maxOfOrNull(selector: (Char) -> R): R? {
     if (isEmpty()) return null
     var maxValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return maxValue
-     
     for (i in 1..lastIndex) {
         val v = selector(this[i])
-        
         if (maxValue < v) {
             maxValue = v
         }
@@ -1286,8 +1262,6 @@ public inline fun <R : Comparable<R>> CharSequence.maxOfOrNull(selector: (Char)
 public inline fun <R> CharSequence.maxOfWith(comparator: Comparator<in R>, selector: (Char) -> R): R {
     if (isEmpty()) throw NoSuchElementException()
     var maxValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return maxValue
     for (i in 1..lastIndex) {
         val v = selector(this[i])
         if (comparator.compare(maxValue, v) < 0) {
@@ -1308,8 +1282,6 @@ public inline fun <R> CharSequence.maxOfWith(comparator: Comparator<in R>, selec
 public inline fun <R> CharSequence.maxOfWithOrNull(comparator: Comparator<in R>, selector: (Char) -> R): R? {
     if (isEmpty()) return null
     var maxValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return maxValue
     for (i in 1..lastIndex) {
         val v = selector(this[i])
         if (comparator.compare(maxValue, v) < 0) {
@@ -1371,6 +1343,8 @@ public inline fun <R : Comparable<R>> CharSequence.minBy(selector: (Char) -> R):
  * Returns the smallest value among all values produced by [selector] function
  * applied to each character in the char sequence.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the char sequence is empty.
  */
 @SinceKotlin("1.4")
@@ -1380,15 +1354,9 @@ public inline fun <R : Comparable<R>> CharSequence.minBy(selector: (Char) -> R):
 public inline fun CharSequence.minOf(selector: (Char) -> Double): Double {
     if (isEmpty()) throw NoSuchElementException()
     var minValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return minValue
-    if (minValue.isNaN()) return minValue 
     for (i in 1..lastIndex) {
         val v = selector(this[i])
-        if (v.isNaN()) return v
+        minValue = minOf(minValue, v)
-        if (minValue > v) {
-            minValue = v
-        }
     }
     return minValue
 }
@@ -1397,6 +1365,8 @@ public inline fun CharSequence.minOf(selector: (Char) -> Double): Double {
  * Returns the smallest value among all values produced by [selector] function
  * applied to each character in the char sequence.
  * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+ * 
  * @throws NoSuchElementException if the char sequence is empty.
  */
 @SinceKotlin("1.4")
@@ -1406,15 +1376,9 @@ public inline fun CharSequence.minOf(selector: (Char) -> Double): Double {
 public inline fun CharSequence.minOf(selector: (Char) -> Float): Float {
     if (isEmpty()) throw NoSuchElementException()
     var minValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return minValue
-    if (minValue.isNaN()) return minValue 
     for (i in 1..lastIndex) {
         val v = selector(this[i])
-        if (v.isNaN()) return v
+        minValue = minOf(minValue, v)
-        if (minValue > v) {
-            minValue = v
-        }
     }
     return minValue
 }
@@ -1432,12 +1396,8 @@ public inline fun CharSequence.minOf(selector: (Char) -> Float): Float {
 public inline fun <R : Comparable<R>> CharSequence.minOf(selector: (Char) -> R): R {
     if (isEmpty()) throw NoSuchElementException()
     var minValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return minValue
-     
     for (i in 1..lastIndex) {
         val v = selector(this[i])
-        
         if (minValue > v) {
             minValue = v
         }
@@ -1448,6 +1408,8 @@ public inline fun <R : Comparable<R>> CharSequence.minOf(selector: (Char) -> R):
 /**
  * Returns the smallest value among all values produced by [selector] function
  * applied to each character in the char sequence or `null` if there are no characters.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  */
 @SinceKotlin("1.4")
 @OptIn(kotlin.experimental.ExperimentalTypeInference::class)
@@ -1456,15 +1418,9 @@ public inline fun <R : Comparable<R>> CharSequence.minOf(selector: (Char) -> R):
 public inline fun CharSequence.minOfOrNull(selector: (Char) -> Double): Double? {
     if (isEmpty()) return null
     var minValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return minValue
-    if (minValue.isNaN()) return minValue 
     for (i in 1..lastIndex) {
         val v = selector(this[i])
-        if (v.isNaN()) return v
+        minValue = minOf(minValue, v)
-        if (minValue > v) {
-            minValue = v
-        }
     }
     return minValue
 }
@@ -1472,6 +1428,8 @@ public inline fun CharSequence.minOfOrNull(selector: (Char) -> Double): Double?
 /**
  * Returns the smallest value among all values produced by [selector] function
  * applied to each character in the char sequence or `null` if there are no characters.
+ * 
+ * If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
  */
 @SinceKotlin("1.4")
 @OptIn(kotlin.experimental.ExperimentalTypeInference::class)
@@ -1480,15 +1438,9 @@ public inline fun CharSequence.minOfOrNull(selector: (Char) -> Double): Double?
 public inline fun CharSequence.minOfOrNull(selector: (Char) -> Float): Float? {
     if (isEmpty()) return null
     var minValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return minValue
-    if (minValue.isNaN()) return minValue 
     for (i in 1..lastIndex) {
         val v = selector(this[i])
-        if (v.isNaN()) return v
+        minValue = minOf(minValue, v)
-        if (minValue > v) {
-            minValue = v
-        }
     }
     return minValue
 }
@@ -1504,12 +1456,8 @@ public inline fun CharSequence.minOfOrNull(selector: (Char) -> Float): Float? {
 public inline fun <R : Comparable<R>> CharSequence.minOfOrNull(selector: (Char) -> R): R? {
     if (isEmpty()) return null
     var minValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return minValue
-     
     for (i in 1..lastIndex) {
         val v = selector(this[i])
-        
         if (minValue > v) {
             minValue = v
         }
@@ -1530,8 +1478,6 @@ public inline fun <R : Comparable<R>> CharSequence.minOfOrNull(selector: (Char)
 public inline fun <R> CharSequence.minOfWith(comparator: Comparator<in R>, selector: (Char) -> R): R {
     if (isEmpty()) throw NoSuchElementException()
     var minValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return minValue
     for (i in 1..lastIndex) {
         val v = selector(this[i])
         if (comparator.compare(minValue, v) > 0) {
@@ -1552,8 +1498,6 @@ public inline fun <R> CharSequence.minOfWith(comparator: Comparator<in R>, selec
 public inline fun <R> CharSequence.minOfWithOrNull(comparator: Comparator<in R>, selector: (Char) -> R): R? {
     if (isEmpty()) return null
     var minValue = selector(this[0])
-    val lastIndex = this.lastIndex
-    if (lastIndex == 0) return minValue
     for (i in 1..lastIndex) {
         val v = selector(this[i])
         if (comparator.compare(minValue, v) > 0) {

libraries/stdlib/test/collections/CollectionTest.kt

@@ -5,6 +5,8 @@
 
 package test.collections
 
+import test.assertIsNegativeZero
+import test.assertIsPositiveZero
 import test.assertStaticAndRuntimeTypeIs
 import kotlin.test.*
 import test.collections.behaviors.*
@@ -909,6 +911,9 @@ class CollectionTest {
 
         assertEquals(Double.NaN, listOf(1, -1, 0).minOf { it.toDouble().pow(0.5) })
         assertEquals(Float.NaN, listOf(1, -1, 0).minOf { it.toFloat().pow(0.5F) })
+
+        assertIsNegativeZero(listOf(1.0, -1.0).shuffled().minOf { it * 0.0 })
+        assertIsNegativeZero(listOf(1.0F, -1.0F).shuffled().minOf { it * 0.0F }.toDouble())
     }
 
     @Test fun minOfWith() {
@@ -934,6 +939,9 @@ class CollectionTest {
 
         assertEquals(16.0, listOf(1, 2, 3, 4, 5).maxOf { (-2.0).pow(it) })
         assertEquals(16.0F, listOf(1, 2, 3, 4, 5).maxOf { (-2.0F).pow(it) })
+
+        assertIsPositiveZero(listOf(1.0, -1.0).shuffled().maxOf { it * 0.0 })
+        assertIsPositiveZero(listOf(1.0F, -1.0F).shuffled().maxOf { it * 0.0F }.toDouble())
     }
 
     @Test fun maxOfWith() {
@@ -946,9 +954,6 @@ class CollectionTest {
         assertEquals(null, emptyList<Int>().maxOfWithOrNull(naturalOrder()) { it })
         // TODO: investigate why no unit-coercion happens here and an explicit 'Unit' is required
         assertFailsWith<NoSuchElementException> { emptyList<Int>().maxOfWith(naturalOrder()) { it }; Unit }
-
-        assertEquals(Double.NaN, listOf(1, -1, 0).maxOf { it.toDouble().pow(0.5) })
-        assertEquals(Float.NaN, listOf(1, -1, 0).maxOf { it.toFloat().pow(0.5F) })
     }
 
 

libraries/stdlib/test/numbers/NaNPropagationTest.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -100,6 +100,24 @@ class NaNPropagationTest {
         )
     }
 
+    @Test
+    fun arrayMinOf() {
+        propagateOf3(
+            { a, b, c -> arrayOf(a, b, c).minOf { it } },
+            { a, b, c -> arrayOf(a, b, c).minOf { it } },
+            "arrayOf().minOf()"
+        )
+    }
+    
+    @Test
+    fun arrayMaxOf() {
+        propagateOf3(
+            { a, b, c -> arrayOf(a, b, c).maxOf { it } },
+            { a, b, c -> arrayOf(a, b, c).maxOf { it } },
+            "arrayOf().maxOf()"
+        )
+    }
+
     @Test
     fun primitiveArrayMin() {
         propagateOf2(
@@ -118,6 +136,34 @@ class NaNPropagationTest {
         )
     }
 
+    @Test
+    fun primitiveArrayMinOf() {
+        propagateOf3(
+            { a, b, c -> doubleArrayOf(a, b, c).minOf { it } },
+            { a, b, c -> floatArrayOf(a, b, c).minOf { it } },
+            "primitiveArrayOf().minOf()"
+        )
+        propagateOf3(
+            { a, b, c -> val arr = doubleArrayOf(a, b, c); intArrayOf(0, 1, 2).minOf { arr[it] } },
+            { a, b, c -> val arr = floatArrayOf(a, b, c); intArrayOf(0, 1, 2).minOf { arr[it] } },
+            "intArrayOf().minOf()"
+        )
+    }
+
+    @Test
+    fun primitiveArrayMaxOf() {
+        propagateOf3(
+            { a, b, c -> doubleArrayOf(a, b, c).maxOf { it } },
+            { a, b, c -> floatArrayOf(a, b, c).maxOf { it } },
+            "primitiveArrayOf().maxOf()"
+        )
+        propagateOf3(
+            { a, b, c -> val arr = doubleArrayOf(a, b, c); intArrayOf(0, 1, 2).maxOf { arr[it] } },
+            { a, b, c -> val arr = floatArrayOf(a, b, c); intArrayOf(0, 1, 2).maxOf { arr[it] } },
+            "intArrayOf().maxOf()"
+        )
+    }
+
     @Test
     fun listMin() {
         propagateOf2(
@@ -136,6 +182,24 @@ class NaNPropagationTest {
         )
     }
 
+    @Test
+    fun listMinOf() {
+        propagateOf3(
+            { a, b, c -> listOf(a, b, c).minOf { it } },
+            { a, b, c -> listOf(a, b, c).minOf { it } },
+            "listOf().minOf()"
+        )
+    }
+
+    @Test
+    fun listMaxOf() {
+        propagateOf3(
+            { a, b, c -> listOf(a, b, c).maxOf { it } },
+            { a, b, c -> listOf(a, b, c).maxOf { it } },
+            "listOf().maxOf()"
+        )
+    }
+
     @Test
     fun sequenceMin() {
         propagateOf2(
@@ -154,6 +218,23 @@ class NaNPropagationTest {
         )
     }
 
+    @Test
+    fun sequenceMinOf() {
+        propagateOf3(
+            { a, b, c -> sequenceOf(a, b, c).minOf { it } },
+            { a, b, c -> sequenceOf(a, b, c).minOf { it } },
+            "sequenceOf().minOf()"
+        )
+    }
+
+    @Test
+    fun sequenceMaxOf() {
+        propagateOf3(
+            { a, b, c -> sequenceOf(a, b, c).maxOf { it } },
+            { a, b, c -> sequenceOf(a, b, c).maxOf { it } },
+            "sequenceOf().maxOf()"
+        )
+    }
 }
 
 class NaNTotalOrderTest {

libraries/stdlib/test/testUtils.kt

@@ -1,10 +1,12 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
 package test
 
+import kotlin.math.withSign
+import kotlin.test.assertEquals
 import kotlin.test.assertTrue
 import kotlin.test.fail
 
@@ -27,4 +29,13 @@ fun assertArrayContentEquals(expected: CharArray, actual: CharArray, message: St
 fun assertArrayContentEquals(expected: UIntArray, actual: UIntArray, message: String? = null)     = assertTrue(expected contentEquals actual, message)
 fun assertArrayContentEquals(expected: ULongArray, actual: ULongArray, message: String? = null)   = assertTrue(expected contentEquals actual, message)
 fun assertArrayContentEquals(expected: UShortArray, actual: UShortArray, message: String? = null) = assertTrue(expected contentEquals actual, message)
-fun assertArrayContentEquals(expected: UByteArray, actual: UByteArray, message: String? = null)   = assertTrue(expected contentEquals actual, message)
+fun assertArrayContentEquals(expected: UByteArray, actual: UByteArray, message: String? = null)   = assertTrue(expected contentEquals actual, message)
+
+fun assertIsNegativeZero(value: Double) {
+    assertEquals(-0.0, value)
+    assertEquals(-1.0, 1.0.withSign(value))
+}
+fun assertIsPositiveZero(value: Double) {
+    assertEquals(0.0, value)
+    assertEquals(1.0, 1.0.withSign(value))
+}

libraries/tools/kotlin-stdlib-gen/src/templates/Aggregates.kt

@@ -562,9 +562,9 @@ object Aggregates : TemplateGroupBase() {
                     Returns the ${if (op == "max") "largest" else "smallest"} value among all values produced by [selector] function 
                     applied to each ${f.element} in the ${f.collection}${" or `null` if there are no ${f.element.pluralize()}".ifOrEmpty(nullable)}.
                     """ +
-//                    """
+                    """
-//                    If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
+                    If any of values produced by [selector] function is `NaN`, the returned result is `NaN`.
-//                    """.ifOrEmpty(isFloat) +
+                    """.ifOrEmpty(isFloat) +
                     """
                     @throws NoSuchElementException if the ${f.collection} is empty.
                     """.ifOrEmpty(!nullable)
@@ -574,19 +574,20 @@ object Aggregates : TemplateGroupBase() {
                 returns(selectorType + "?".ifOrEmpty(nullable))
                 val doOnEmpty = if (nullable) "return null" else "throw NoSuchElementException()"
                 val acc = op + "Value"
-                val cmp = if (op == "max") "<" else ">"
+                val cmpBlock = if (isFloat)
+                    """$acc = ${op}Of($acc, v)"""
+                else
+                    """if ($acc ${if (op == "max") "<" else ">"} v) {
+                            $acc = v
+                        }"""
                 body {
                     """
                     val iterator = iterator()
                     if (!iterator.hasNext()) $doOnEmpty
                     var $acc = selector(iterator.next())
-                    ${"if ($acc.isNaN()) return $acc".ifOrEmpty(isFloat)}
                     while (iterator.hasNext()) {
                         val v = selector(iterator.next())
-                        ${"if (v.isNaN()) return v".ifOrEmpty(isFloat)}
+                        $cmpBlock
-                        if ($acc $cmp v) {
-                            $acc = v
-                        }
                     }
                     return $acc
                     """
@@ -596,15 +597,9 @@ object Aggregates : TemplateGroupBase() {
                     if (isEmpty()) $doOnEmpty
         
                     var $acc = selector(this[0])
-                    val lastIndex = this.lastIndex
-                    if (lastIndex == 0) return $acc
-                    ${"if ($acc.isNaN()) return $acc".ifOrEmpty(isFloat)} 
                     for (i in 1..lastIndex) {
                         val v = selector(this[i])
-                        ${"if (v.isNaN()) return v".ifOrEmpty(isFloat)}
+                        $cmpBlock
-                        if ($acc $cmp v) {
-                            $acc = v
-                        }
                     }
                     return $acc
                     """
@@ -668,8 +663,6 @@ object Aggregates : TemplateGroupBase() {
                     if (isEmpty()) $doOnEmpty
         
                     var $acc = selector(this[0])
-                    val lastIndex = this.lastIndex
-                    if (lastIndex == 0) return $acc
                     for (i in 1..lastIndex) {
                         val v = selector(this[i])
                         if (comparator.compare($acc, v) $cmp 0) {