diff --git a/lslopt/lslfoldconst.py b/lslopt/lslfoldconst.py
index 739ed8b..486e2a7 100644
--- a/lslopt/lslfoldconst.py
+++ b/lslopt/lslfoldconst.py
@@ -20,6 +20,7 @@
 import lslfuncs
 import math
 from lslparse import warning
+from lslfuncparams import OptimizeParams
 
 class foldconst(object):
 
@@ -179,6 +180,9 @@ class foldconst(object):
 
                 if (Invertible[0] or Invertible[1]) and ParentIsNegation:
                     # !(!a|b)  ->  a&-!b or a&!b
+                    # This deals with the part after the first !, transforming
+                    # it into (!a|!!b) so that the outer node can optimize the
+                    # negated version to a simple &.
                     for a in (0, 1):
                         if not Invertible[a]:
                             child[a] = {'nt':'!', 't':'integer',
@@ -344,7 +348,7 @@ class foldconst(object):
         if nt == '!':
             self.FoldTree(child, 0)
             self.FoldCond(child, 0, True)
-            # !! does *not* cancel out (unless in cond), but !!! can be simplified to !
+            # !! does *not* cancel out (unless in cond)
             subexpr = child[0]
             snt = subexpr['nt']
             if 'SEF' in subexpr:
@@ -926,8 +930,7 @@ class foldconst(object):
                 if child[idx]['nt'] != 'CONST':
                     CONSTargs = False
 
-            # TODO: Find some way to convert keys to "" e.g. llListen("", NULL_KEY, "")
-            # TODO: Find some way to convert PI to 4 in llSensor[Repeat]
+            OptimizeParams(node, self.symtab[0][node['name']])
             if 'Fn' in self.symtab[0][node['name']]:
                 # Guaranteed to be side-effect free if the children are.
                 if SEFargs:
diff --git a/lslopt/lslfuncparams.py b/lslopt/lslfuncparams.py
new file mode 100644
index 0000000..06872eb
--- /dev/null
+++ b/lslopt/lslfuncparams.py
@@ -0,0 +1,43 @@
+#    (C) Copyright 2015 Sei Lisa. All rights reserved.
+#
+#    This file is part of LSL PyOptimizer.
+#
+#    LSL PyOptimizer is free software: you can redistribute it and/or
+#    modify it under the terms of the GNU General Public License as
+#    published by the Free Software Foundation, either version 3 of the
+#    License, or (at your option) any later version.
+#
+#    LSL PyOptimizer is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with LSL PyOptimizer. If not, see <http://www.gnu.org/licenses/>.
+
+# Transform function parameters to shorter equivalents where possible.
+# This is dependent on the LSL function library.
+
+from lslcommon import Key#, Vector, Quaternion
+import lslfuncs
+
+def OptimizeParams(node, sym):
+    assert node['nt'] == 'FNCALL'
+    params = node['ch']
+    name = node['name']
+
+    if name in ('llSensor', 'llSensorRepeat'):
+        # The cutoff value is at a bit less than 3.1275 for some reason,
+        # but we use 3.14159.
+        if params[4]['nt'] == 'CONST' and params[4]['t'] == 'float' and params[4]['value'] > 3.14159:
+            params[4]['value'] = 4.0
+
+    types = sym['ParamTypes']
+    if name != 'llMessageLinked':
+        # Transform invalid/null keys to "" e.g. llGetOwnerKey(NULL_KEY) -> llGetOwnerKey("")
+        # llMessageLinked is the exception.
+        for i in range(len(types)):
+            if types[i] == 'key':
+                if params[i]['nt'] == 'CONST':
+                    if not lslfuncs.cond(Key(params[i]['value'])):
+                        params[i]['value'] = u""
diff --git a/lslopt/lsloptimizer.py b/lslopt/lsloptimizer.py
index b7c005e..bdcce54 100644
--- a/lslopt/lsloptimizer.py
+++ b/lslopt/lsloptimizer.py
@@ -18,7 +18,7 @@
 # Optimizer class that wraps and calls the other parts.
 
 import lslfuncs
-from lslfuncs import Key, Vector, Quaternion
+from lslcommon import Key, Vector, Quaternion
 
 from lslfoldconst import foldconst
 from lslrenamer import renamer