-interpretation "exT \fst" 'pi1 = (pi1exP _ _).
-interpretation "exT \fst" 'pi1a x = (pi1exP _ _ x).
-interpretation "exT \fst" 'pi1b x y = (pi1exP _ _ x y).
-interpretation "exT \snd" 'pi2 = (pi2exP _ _).
-interpretation "exT \snd" 'pi2a x = (pi2exP _ _ x).
-interpretation "exT \snd" 'pi2b x y = (pi2exP _ _ x y).
+interpretation "exP \fst" 'pi1 = (pi1exP _ _).
+interpretation "exP \fst" 'pi1a x = (pi1exP _ _ x).
+interpretation "exP \fst" 'pi1b x y = (pi1exP _ _ x y).
+interpretation "exP \snd" 'pi2 = (pi2exP _ _).
+interpretation "exP \snd" 'pi2a x = (pi2exP _ _ x).
+interpretation "exP \snd" 'pi2b x y = (pi2exP _ _ x y).