ibc i (IBCHeader tgt n) f = return f { ibc_hdrs = (tgt, n) : ibc_hdrs f }
ibc i (IBCHeader tgt n) f = return f { ibc_hdrs = (tgt, n) : ibc_hdrs f }
ibc i (IBCHeader tgt n) f = return f { ibc_hdrs = (tgt, n) : ibc_hdrs f }