add rshift (>>) : SLT x Int -> STL as next(self, i)

stl/ast.py

@@ -37,6 +37,16 @@ class AST(object):
             return self.arg
         return Neg(self)
 
+    def __rshift__(self, t):
+        if self in (BOT, TOP):
+            return self
+
+        phi = self
+        for _ in range(t):
+            phi = Next(phi)
+
+        return phi
+
     @property
     def children(self):
         return tuple()

stl/utils.py

@@ -207,9 +207,7 @@ def iff(x, y):
 
 
 def next(phi, i=1):
-    for _ in range(i):
+    return phi >> i
-        phi = Next(phi)
-    return phi
 
 
 def timed_until(phi, psi, lo, hi):