# Binary String pattern matching

Andreas Schultz andreas.schultz@REDACTED
Wed Dec 9 20:55:57 CET 2020

```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

--

Principal Engineer

t: +49 391 819099-224

------------------------------- enabling your networks
-----------------------------

Travelping GmbH
Roentgenstraße 13
39108 Magdeburg
Germany

t: +49 391 819099-0
f: +49 391 819099-299

e: info@REDACTED
w: https://www.travelping.com/
Company registration: Amtsgericht Stendal
Managing Director: Holger Winkelmann
Reg. No.: HRB 10578
VAT ID: DE236673780
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://erlang.org/pipermail/erlang-questions/attachments/20201209/077f17e1/attachment.htm>
```