implementation of suffix

Ulf Wiger (AL/EAB) <>
Fri May 27 15:42:51 CEST 2005



The implementation of lists:suffix/2 is as follows:


suffix(Suffix, Suffix) -> true;
suffix(Suffix, [_|Tail]) ->
    suffix(Suffix, Tail);
suffix(_, []) -> false.


The programming style in lists.erl seems to be to be very conservative
about using type guards. One objection to this could be that it makes 
it more difficult for Dialyzer to derive good type information from one of 
the most frequently used modules, but in the case of suffix/2, I would
say that it also violates the Principle of Least Astonishment:

()13> lists:suffix(a,[1,2,3|a]).
true
()14> lists:suffix(b,[1,2,3|a]).
** exited: {function_clause,[{lists,suffix,[b,a]},
                             {erl_eval,do_apply,5},
                             {shell,exprs,6},
                             {shell,eval_loop,3}]} **

=ERROR REPORT==== 27-May-2005::15:36:23 ===
Error in process <0.95.0> on node '' with exit value: {function_clause,[{lists,suffix,[b,a]},{erl_eval,do_apply,5},{shell,exprs,6},{shell,eval_loop,3}]}


Bug or feature?

/Uffe




More information about the erlang-questions mailing list