This is something I've wanted for a long time. If we have a `compare`
function on all the main type modules like String, Atom, Binary, Integer,
Float, etc... then we'd be able to pass in the module atom as a witness
through functions along with the value type, it is one of the best ways you
can do type based programming in a purely dynamic language.
.
On Thursday, October 12, 2017 at 7:05:57 PM UTC-6, miwee wrote:
>
> consider following code segment
>
> def valid_row?(%{"acu" => acu}) when is_number(acu) do
> acu_limit = Application.get_env(:beam_checker, :acu_limit)
> acu > acu_limit
> end
>
> since elixir/erlang comparison operator is very broad, the above code will
> never throw any exception irrespective of what is the data type or value
> for acu and acu_limit. But the end result is totally unexpected in cases
> where wrong types are supplied. two actual error cases which happened (and
> took some time to discover due to no exception) :
> 1) acu_limit was not defined in config, hence acu_limit got value nil
> 2) acu_limit was defined as string value in config
>
> possible options for discussion:
> 1) can we have Integer.compare and Float.compare functions. That way
> whenever numeric comparisons are needed, these dedicated functions can be
> used. (preferred)
> 2) strict comparison version of > and < operators (something along the
> lines of == and ===, but for comparison)
>
> option not for discussion
> 1) make a private comparison function, which throws an error if input
> values are not numbers. this is what I currently did.
>
> thanks
> miwee
>
>
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