diff --git a/stl/utils.py b/stl/utils.py
index 88b0395..3a2b938 100644
--- a/stl/utils.py
+++ b/stl/utils.py
@@ -48,7 +48,7 @@ def _ast_lens(phi, *, pred, focus=lens(), focus_lens):
     psi = focus.get(state=phi)
     ret_lens = [focus.add_lens(l) for l in focus_lens(psi)] if pred(psi) else []
 
-    if isinstance(psi, LinEq):
+    if isinstance(psi, (LinEq, stl.ast.AtomicPred)):
         return ret_lens
 
     child_lenses = list(_child_lens(psi, focus=focus))
@@ -58,6 +58,7 @@ def _ast_lens(phi, *, pred, focus=lens(), focus_lens):
 
 
 lineq_lens = fn.partial(ast_lens, pred=type_pred(LinEq))
+AP_lens = fn.partial(ast_lens, pred=type_pred(stl.ast.AtomicPred))
 and_or_lens = fn.partial(ast_lens, pred=type_pred(And, Or))
 
 def terms_lens(phi:"STL", bind=True) -> lens:
@@ -117,4 +118,9 @@ def to_mtl(phi):
     ap_map = {to_ap(i): leq for i, leq in enumerate(focus.get_all())}
     lineq_map = {v:k for k,v in ap_map.items()}
     return focus.modify(lineq_map.get), ap_map
+
+
+def from_mtl(phi, ap_map):
+    focus = lineq_lens(phi)
+    return focus.modify(ap_map.get)