added horizon option to discretize

stl/utils.py

@@ -101,13 +101,14 @@ def implicit_validity_domain(phi, trace):
 def require_discretizable(func):
     @wraps(func)
     def _func(phi, dt, *args, **kwargs):
+        if 'horizon' not in kwargs:
             assert is_discretizable(phi, dt)
         return func(phi, dt, *args, **kwargs)
 
     return _func
 
 
-def scope(phi, dt, *, _t=0):
+def scope(phi, dt, *, _t=0, horizon=oo):
     if isinstance(phi, Next):
         _t += dt
     elif isinstance(phi, (G, F)):
@@ -115,32 +116,44 @@ def scope(phi, dt, *, _t=0):
     elif isinstance(phi, Until):
         _t += float('inf')
 
-    return max((scope(c, dt, _t=_t) for c in phi.children), default=_t)
+    _scope = max((scope(c, dt, _t=_t) for c in phi.children), default=_t)
+    return min(_scope, horizon)
 
 
 # Code to discretize a bounded STL formula
 
 
 @require_discretizable
-def discretize(phi, dt, distribute=False):
-    phi = _discretize(phi, dt)
+def discretize(phi, dt, distribute=False, *, horizon=None):
+    if horizon is None:
+        horizon = oo
+
+    phi = _discretize(phi, dt, horizon)
     return _distribute_next(phi) if distribute else phi
 
 
-def _discretize(phi, dt):
+def _discretize(phi, dt, horizon):
     if isinstance(phi, (LinEq, AtomicPred, _Top, _Bot)):
         return phi
 
-    children = tuple(_discretize(arg, dt) for arg in phi.children)
+    if not isinstance(phi, (F, G, Until)):
+        children = tuple(_discretize(arg, dt, horizon) for arg in phi.children)
         if isinstance(phi, (And, Or)):
             return bind(phi).args.set(children)
         elif isinstance(phi, (Neg, Next)):
             return bind(phi).arg.set(children[0])
 
+        raise NotImplementedError
+
+    elif isinstance(phi, Until):
+        raise NotImplementedError
+
     # Only remaining cases are G and F
-    psi = children[0]
-    l, u = round(phi.interval.lower / dt), round(phi.interval.upper / dt)
-    psis = (next(psi, i) for i in range(l, u + 1))
+    upper = min(phi.interval.upper, horizon)
+    l, u = round(phi.interval.lower / dt), round(upper / dt)
+
+    psis = (next(_discretize(phi.arg, dt, horizon - i), i)
+            for i in range(l, u + 1))
     opf = andf if isinstance(phi, G) else orf
     return opf(*psis)
 
@@ -174,7 +187,6 @@ def is_discretizable(phi, dt):
         _interval_discretizable(c.interval, dt) for c in phi.walk()
         if isinstance(c, (F, G)))
 
-
 # EDSL