let debug_print = if debug then prerr_endline else ignore
(* searches a coercion fron src to tgt in the !coercions list *)
let look_for_coercion src tgt =
try
let debug_print = if debug then prerr_endline else ignore
(* searches a coercion fron src to tgt in the !coercions list *)
let look_for_coercion src tgt =
try