Don't attempt to sort empty or singleton lists, also fix missed inter…

…nal variable name changes

gm-stream/objects/obj_tests/Create_0.gml

@@ -376,6 +376,36 @@ function testSort() {
 	return new TestResult(testName, true, "");
 }
 
+function testSortEmptyList() {
+	var testName = "Sort Empty List";
+	var initialArray = [];
+
+	var result = stream_of(initialArray)
+					.sort()
+					.collectJoining();
+
+	if (result != "") {
+		return new TestResult(testName, false, "expected result to be empty");
+	}
+
+	return new TestResult(testName, true, "");
+}
+
+function testSortMonoList() {
+	var testName = "Sort Mono List";
+	var initialArray = ["A"];
+
+	var result = stream_of(initialArray)
+					.sort()
+					.collectJoining();
+
+	if (result != "A") {
+		return new TestResult(testName, false, "expected result to be same as input");
+	}
+
+	return new TestResult(testName, true, "");
+}
+
 function testSortNumeric() {
 	var testName = "Sort Simple (Numeric)";
 	var initialArray = [3, 1, 20];
@@ -498,7 +528,7 @@ totalCount = 0;
 failedCount = 0;
 testSuite = [testListToStream, testArrayToStream, testCollectList, testCollectArray, testDistinct, testCount, testFilter, testMap, testAllMatchTrue, testAllMatchFalse,
 			 testAnyMatchTrue, testAnyMatchFalse, testForEach, testCollectJoining, testCollectJoiningDelimiter, testCollectJoiningDelimiterPrefix, 
-			 testCollectJoiningDelimiterPrefixSuffix, testFindFirstEmpty, testFindFirst, testSort, testSortNumeric, testSortComparator, testNoneMatchTrue, 
+			 testCollectJoiningDelimiterPrefixSuffix, testFindFirstEmpty, testFindFirst, testSort, testSortEmptyList, testSortMonoList,  testSortNumeric, testSortComparator, testNoneMatchTrue, 
 			 testNoneMatchFalse, testQueueToStream, testStackToStream, testFold, testReduce, testReduceEmpty];
 show_debug_message("\nBeginning test suite\n");
 for (var i = 0; i < array_length(testSuite); i++) {

gm-stream/scripts/scr_gmstream/scr_gmstream.gml

@@ -46,14 +46,16 @@ function GmStream(_gms_data) constructor {
 	}
 
 	sort = function(comparatorFunction) {
-		if (is_undefined(comparatorFunction) && isSorted == false) {
-			ds_list_sort(gms_data, true);
-			isSorted = true;
-		} else {
-			// Don't check or set isSorted in this case as a new comparator function could re-sort us
-			var result = self.mergesort(gms_data, comparatorFunction);
-			ds_list_copy(gms_data, result);
-			ds_list_destroy(result);
+		if (ds_list_size(gms_data) > 1) {
+			if (is_undefined(comparatorFunction) && isSorted == false) {
+				ds_list_sort(gms_data, true);
+				isSorted = true;
+			} else {
+				// Don't check or set isSorted in this case as a new comparator function could re-sort us
+				var result = self.mergesort(gms_data, comparatorFunction);
+				ds_list_copy(gms_data, result);
+				ds_list_destroy(result);
+			}
 		}
 		return self;
 	}
@@ -144,8 +146,8 @@ function GmStream(_gms_data) constructor {
 
 	fold = function(initialValue, foldFunction) {
 		var result = initialValue;
-		for (var i = 0; i < ds_list_size(data); i++) {
-			result = foldFunction(result, data[| i]);
+		for (var i = 0; i < ds_list_size(gms_data); i++) {
+			result = foldFunction(result, gms_data[| i]);
 		}
 		self.clean_up();
 		return result;
@@ -164,13 +166,13 @@ function GmStream(_gms_data) constructor {
 	}
 
 	reduce = function(foldFunction) {
-		if (ds_list_size(data) == 0) {
+		if (ds_list_size(gms_data) == 0) {
 			self.clean_up();
 			throw "Cannot reduce an empty stream";
 		}
-		var result = data[| 0];
-		for (var i = 1; i < ds_list_size(data); i++) {
-			result = foldFunction(result, data[| i]);
+		var result = gms_data[| 0];
+		for (var i = 1; i < ds_list_size(gms_data); i++) {
+			result = foldFunction(result, gms_data[| i]);
 		}
 		self.clean_up();
 		return result;