Fix error in PackedSequence

PackedSequence failed to normalize properly sequences like
"1a,0b,1a", which it returned as "a,a" instead of "2a"

1 files changed, 33 insertions, 2 deletions

diff --git a/src/python/lmi/test/util.py b/src/python/lmi/test/util.py
index 7574751..6bce3c6 100644
--- a/src/python/lmi/test/util.py
+++ b/src/python/lmi/test/util.py
@@ -420,8 +420,20 @@ class PackedSequence(object):
                 return "%s%s" % (n, self.item)
             return ""
 
+        def __add__(self, other):
+            if self.item == other.item:
+                return self.__class__(self.item, self.num + other.num)
+            else:
+                raise TypeError("items cannot be added")
+
+        def __nonzero__(self):
+            return bool(self.num)
+
+        def __repr__(self):
+            return "%s(%s,%s)" % (self.__class__.__name__, self.item, self.num)
+
     def __init__(self, seq=None):
-        self._items = self._parse(seq)
+        self._items = self._squash(self._parse(seq)) if seq else []
 
     def __iter__(self):
         return self
@@ -432,11 +444,30 @@ class PackedSequence(object):
     def __str__(self):
         return ",".join([str(i) for i in self._items])
 
+    def _squash(self, sparse):
+        """
+        Squash items, i.e. "b,1a,0a,0a,a,2a" to "1b,4a"
+        """
+        comp = []
+        while sparse:
+            nxt = sparse.pop()
+            if not nxt:             # skip zero items
+                continue
+            elif comp:
+                try:
+                    comp[-1] += nxt
+                except TypeError:   # cannot add -> append
+                    comp.append(nxt)
+            else:
+                comp.append(nxt)
+        comp.reverse()
+        return comp
+
     def _parse(self, seq):
         """
         Parse sequence string
         """
-        return [self._parse1(itm) for itm in seq.split(",")] if seq else []
+        return [self._parse1(itm) for itm in seq.split(",")]
 
     def _parse1(self, itm):
         ns = ""