test with loop in erlang - erlang

Question

I have a list of values ​​ "Z0010", "Z0011", "Z0012", "Z0013" "Z0014", "Z0015", "Z0016", "Z0017", "Z0018", "Z0019"
I want to develop a function that takes a value in parameter
and I want to do a test in my function if the value passed as a parameter is equal to a value in the list in this cases it will show "existe" if not it displays "not existe"
I try with :
test(Token)->
case get_user_formid_by_token(Token) of
{ok, H} ->
FormId=string:substr(H, 2, length(H)),
Form=string:to_integer(FormId),
case verify (0019,1,Form) of
{ok}->io:format("existe");
{notok}->io:format("not existe")
end;
{error, notfound}-> io:format("qq")
end.
verify(VariableLength,VariableIncrement,FormId)->
lists:map(fun(I) -> if I =:= FormId ->
{ok};
I =/= FormId ->
{notok}
end
end,
lists:seq(0010, VariableLength, VariableIncrement)).
but when I execute this code it displays :
1> model:test("21137900").
** exception error: no case clause matching [{notok},
{notok},
{notok},
{notok},
{notok},
{notok},
{notok},
{notok},
{notok},
{notok}]
in function model:test/1
I try now with this solution :
get_user_formid_by_token(Token) ->
Q = qlc:q([{X#person.formid} || X <- mnesia:table(person),
X#person.token =:= Token]),
case do(Q) of
[{H}] ->
{ok, H};
[] ->
{error, notfound}
end.
test(Token)->
case get_user_formid_by_token(Token) of
{ok, H} ->
io:format("~s~n",[H]),
FormId=string:substr(H, 5, length(H)),
io:format("~s~n",[FormId]),
Form=string:to_integer(FormId),
io:format("~p~n",[Form]),
lists:member(Form, lists:seq(313, 320, 1));
{error, notfound}-> io:format("qq")
end.
but when I test I have this message in the console:
1> model:test("21137900").
Z000313
313
{313,[]}
false
the result should be true and not false
I think that Form=string:to_integer(FormId), it not return in this case 313
and another thing I want to add in my code
for example if H equal "Z000010" FormId=string:substr(H, 2, length(H)),
it return "000010"
Now I want to eliminate the first zero before the first integer not null so extarct 0000
before 1

Answer 1

lists:map/2 takes one list and creates a new list with the same number of values, so your list of 10 values is transformed into a list of 10 {ok} or {notok} tuples.
You probably want lists:member/2 instead.
5> lists:member(0, lists:seq(1, 3, 1)).
false
6> lists:member(3, lists:seq(1, 3, 1)).
true
7> lists:map(fun(X) -> ok end, lists:seq(1, 3, 1)).
[ok,ok,ok]

Answer 2

Have a look at the documentation (http://www.erlang.org/doc/man/string.html#to_integer-1):
to_integer(String) -> {Int, Rest} | {error, Reason}
Types:
String = string()
Int = integer()
Rest = string()
Reason = no_integer | not_a_list
So to_integer returns a tuple containing the number that was consumed from the string and the rest of the string. You can even tell from your test output where it says {313,[]}. In order to get the value of the number bound to your Formvariable, you need to decompose the tuple, which is typically done by pattern matching:
{Form,_Rest}=string:to_integer(FormId)
Now your Form will contain only the number 313.
The string:to_integerfunction will also happily eat the leading zeroes:
1> {Form, _} = string:to_integer("000010"), Form.
10