[erlang-questions] chained functions

[Reynaldo Baquerizo]

A friend of mine asked:

##
If you have functions that return {ok, Result} | {error, Reason}
how do you chained them? So that you have:

w(x(y(z(...))))

without building a staircasing. Something that would be done in Haskell
with monads.
##

I would probably go for:

x({ok, Value}) ->
  NewValue = <do something with Value>,
  {ok, NewValue};
x({error, Reason}) ->
  {error, Reason}.

in each function

which brings me other question, when do you tag return values?

I tend to only use tagged return values with impure functions, were an
error is more likely due to side effects.

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Reynaldo