ibc i (IBCFragile n r)   f = return f { ibc_fragile    = (n,r)  : ibc_fragile f }
ibc i (IBCFragile n r)   f = return f { ibc_fragile    = (n,r)  : ibc_fragile f }
ibc i (IBCFragile n r)   f = return f { ibc_fragile    = (n,r)  : ibc_fragile f }