🍒 ZSP9-Poznań Umultowo – Szkoła na Umultowie

you can use try expression or catch expression try expression is strightforward, if you ignore the awkward erlang grammer that is. after consdering the various code, i come up with this code. here is the verbose code. it's too verbose and ugly but i think alternatives are worse. well, it's not bad. catch exprs catch expression evaluate exprs and return its value on no exception. use try expression's of section to pattern match the error value. putting it all togather, it's very verbose to handle errors in erlang. well, at least, i understand the error handling of erlang.{/INSERTKEYS}{/PARAGRAPH} another type of error is although the query paramters are present, it has a string that cannot be parsed as an integer. but i want to deal the the error. erlang has exception like many other langauges. for exceptions of class throw, that is the code called throw term , term is returned. my guess is to keep the backward compatibility. but i feel some oddities on erlang's exception and that is the concept of class. the simplest code that assume no error will be like this. suppose, the users forget the query parameters. it can be done by case expression or function. {PARAGRAPH}{INSERTKEYS}so hopefully, the higher framework catch these exceptions and restart the process. but if you care, that is, you want to run some code on the condition of exception, things get verbose. we can do condional branching with either case expression or function pattern match. walkthrough of hello world http server with erlang, cowboy, and rebar3 instead of returning the hello world, we're going to return the sum of two query parameter a, b. the catch expression. but what if the caller want to deal with the error? let's quickly borrow a code from the hello world http server i explained in the previous article. we have to use the patter match for the conditional execution. whichever you use, it became quite verbose and boilar-plate. try expression can have of section and it will be evaluated only on no exception in exprs. if you don't care about exception, you need to do nothing. the erlang has three class of exception: error, exit, and throw.