From 6ec4e81e0202118fae17b92e1850b78313942fe3 Mon Sep 17 00:00:00 2001
From: Rory Yorke <rory.yorke@gmail.com>
Date: Sat, 13 Jan 2018 09:37:44 +0200
Subject: [PATCH] FIX: bdalg.series should reverse order of arguments in
 product

Also corrected doc comment: scaler -> scalar
---
 control/bdalg.py            |  6 +++---
 control/tests/bdalg_test.py | 17 +++++++++++++++++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/control/bdalg.py b/control/bdalg.py
index 3edf287f7..0d1a5e8c4 100644
--- a/control/bdalg.py
+++ b/control/bdalg.py
@@ -67,7 +67,7 @@ def series(sys1, *sysn):
     Parameters
     ----------
     sys1: scalar, StateSpace, TransferFunction, or FRD
-    *sysn: other scalers, StateSpaces, TransferFunctions, or FRDs
+    *sysn: other scalars, StateSpaces, TransferFunctions, or FRDs
 
     Returns
     -------
@@ -103,7 +103,7 @@ def series(sys1, *sysn):
 
     """
     from functools import reduce
-    return reduce(lambda x, y:x*y, sysn, sys1)
+    return reduce(lambda x, y:y*x, sysn, sys1)
 
 def parallel(sys1, *sysn):
     """
@@ -112,7 +112,7 @@ def parallel(sys1, *sysn):
     Parameters
     ----------
     sys1: scalar, StateSpace, TransferFunction, or FRD
-    *sysn: other scalers, StateSpaces, TransferFunctions, or FRDs
+    *sysn: other scalars, StateSpaces, TransferFunctions, or FRDs
 
     Returns
     -------
diff --git a/control/tests/bdalg_test.py b/control/tests/bdalg_test.py
index f3688efa9..07775cb80 100644
--- a/control/tests/bdalg_test.py
+++ b/control/tests/bdalg_test.py
@@ -237,6 +237,23 @@ def testLists(self):
         np.testing.assert_array_almost_equal(sort(zero(sys1_5)), 
                                              sort(zero(sys1 + sys2 + 
                                                        sys3 + sys4 + sys5)))
+    def testMimoSeries(self):
+        """regression: bdalg.series reverses order of arguments"""
+        g1 = ctrl.ss([],[],[],[[1,2],[0,3]])
+        g2 = ctrl.ss([],[],[],[[1,0],[2,3]])
+        ref = g2*g1
+        tst = ctrl.series(g1,g2)
+        # assert_array_equal on mismatched matrices gives
+        # "repr failed for <matrix>: ..."
+        def assert_equal(x,y):
+            np.testing.assert_array_equal(np.asarray(x),
+                                          np.asarray(y))
+        assert_equal(ref.A, tst.A)
+        assert_equal(ref.B, tst.B)
+        assert_equal(ref.C, tst.C)
+        assert_equal(ref.D, tst.D)
+
+
 def suite():
     return unittest.TestLoader().loadTestsFromTestCase(TestFeedback)