[erlang-questions] Must and May convention

Joe Armstrong <>
Wed Sep 27 12:10:18 CEST 2017


But the source would be ugly

I want to write

    must_read_file(F)

and not

    must(file,read_file,[F])

/Joe

On Wed, Sep 27, 2017 at 11:39 AM, Roman Galeev <> wrote:

> Imo you can do it with:
> must(M,F,A) ->
> case erlang:apply(M,F,A) of
> {ok, Res} -> Res;
> _Err ->
> io:format("Error ~p:~p(~p) ~p",[M, F, A, _Err]),
> exit({must, F, A,})
> end.
>
> In this case, you don't need to make new functions out of existing ones,
> and still get a nice error message.
>
> On Wed, Sep 27, 2017 at 11:30 AM, Karlo Kuna <> wrote:
>
>> could we have something in type specifications that indicates throw case:
>>
>> -spec f_name( Args ) -> .....; throw(TE | TE1 | ....).
>>
>> On Wed, Sep 27, 2017 at 11:25 AM, Attila Rajmund Nohl <
>> > wrote:
>>
>>> 2017-09-27 11:08 GMT+02:00 Joe Armstrong <>:
>>> [...]
>>> > This turns out to be very convenient - I read many files
>>> > in my programs, so it's nice to know that must_read_file
>>> > will print a nice error message and terminate
>>> > if I give it a bad filename.
>>> >
>>> > Note: I can get the program to crash by writing
>>> >
>>> >    {ok, B} = file:read_file(F)
>>> >
>>> > But I don't get a nice error message telling me the filename.
>>> >
>>> > Any takers?
>>>
>>> My problem with all kinds of very common prefixes is that it breaks
>>> function name autocompletion. Or at least makes it harder to use when
>>> I have dozens/hundreds/thousands of function names starting with the
>>> same 3-5 characters - either I have to type those 3-5 characters all
>>> the time plus any more characters to find unique prefix for
>>> autocompletion or have to autocomplete twice (one for the may/must
>>> difference, one for the actual function name). Eclipse (for Java)
>>> helpfully shows the method signature including return value and thrown
>>> exceptions - I think this problem should be solved by the IDEs and not
>>> by naming conventions.
>>> _______________________________________________
>>> erlang-questions mailing list
>>> 
>>> http://erlang.org/mailman/listinfo/erlang-questions
>>>
>>
>>
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>> 
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>>
>>
>
>
> --
> With best regards,
>      Roman Galeev,
>      +420 702 817 968 <+420%20702%20817%20968>
>
> _______________________________________________
> erlang-questions mailing list
> 
> http://erlang.org/mailman/listinfo/erlang-questions
>
>
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