TD.Substval empty : tEmpty subst
While the term is a variable bound in subst, follow its binding. Returns the final term and scope
val create_renaming : unit -> renamingval reset_renaming : renaming -> unitRename the given variable into a variable that is unique within variables known to the given renaming
Apply the substitution to the term. Free variables are renamed using renaming
val fmt : Format.formatter -> t -> unit