Binary String pattern matching

[Andreas Schultz]

Hi,

Short version without input validation, will crash if the input does not
match the expected values:

currency(<<"CHF">>) -> chf;
currency(<<"EUR">>) -> eur;
currency(<<"US">>) -> us.

currrency_to_credits({cur, String}, Acc) ->
    {Value, Currency} = string:to_integer(String),
    {currency(Currency), Acc + Value}.

Andreas

Am Mi., 9. Dez. 2020 um 19:49 Uhr schrieb Java House <java4dev@REDACTED>:

> there is a typo in the example
> currrency_to_credits({cur, << Value , "CHF">>}, Acc)
>   when Value >= <<"1000">>, Value =< <<"10000">> ->
>      {chf, Acc + Value };
> currrency_to_credits({cur, << Value , "EUR">>}, Acc)
>   when Value >= <<"1000">>, Value =< <<"10000">> ->
>      {eur, Acc + Value };
> currrency_to_credits({cur, << Value , "US">>}, Acc)
>   when Value >= <<"1000">>, Value =< <<"10000">> ->
>      {us, Acc + Value };
>
> Στις Τετ, 9 Δεκ 2020 στις 7:17 μ.μ., ο/η Java House <java4dev@REDACTED>
> έγραψε:
>
>> Hello all
>>
>> I am learning Erlang and have stuck to the following problem.
>> How to write a function with pattern matching when the parameter is a
>> binary string.
>>
>> I have a list of binary strings e.g.
>> <<3123CHF>>
>> <<341424343EUR>>
>> <<14143US>>
>>
>> I am trying to create a function that matches according to a pattern.
>>
>> currrency_to_credits({cur, <<A, "CHF">>}, Acc)
>>   when Value >= <<"1000">>, Value =< <<"10000">> ->
>>      {chf, Acc + A};
>> currrency_to_credits({cur, <<A, "EUR">>}, Acc)
>>   when Value >= <<"1000">>, Value =< <<"10000">> ->
>>      {eur, Acc + A};
>> currrency_to_credits({cur, <<A, "US">>}, Acc)
>>   when Value >= <<"1000">>, Value =< <<"10000">> ->
>>      {us, Acc + A};
>>
>> But this does not seem to be the right way.
>> How can I create a pattern for binary string?
>> will it work better for list string? How?
>>
>> Thank you
>> Nikolas
>>
>

-- 

Andreas Schultz

-- 

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