val normalize:
?delta:bool -> ?subst:Cic.substitution -> Cic.context -> Cic.term -> Cic.term
-(* performs an head beta/cast reduction *)
-val head_beta_reduce: Cic.term -> Cic.term
+(* performs an head beta/cast reduction; the default is to not perform
+ delta reduction *)
+val head_beta_reduce: ?delta:bool -> Cic.term -> Cic.term