[erlang-questions] Re: Concept of Side-effect
Fri Sep 18 05:15:40 CEST 2009
It is the idea that it is modifying state outside the function. So
printing to the console is a side-effect, it is externalized state.
Kaiduan Xie wrote:
> Thanks Benjamin, but sometimes printing out to the console is really
> what you want. Maybe this is not a good example :)
> On Thu, Sep 17, 2009 at 10:18 PM, Benjamin Tolputt
> <btolputt@REDACTED> wrote:
>> Kaiduan Xie wrote:
>>> Thanks a lot for the great examples. But I can not understand the following one,
>>> add(X,Y) ->
>>> add_effects(X,Y) ->
>>> What side-effect add_effects generates? Why we say io:format()
>>> generates side-effect?
>> The side-effect is that there is something printed to the console (or
>> stdout). If there were another function (say 'print_screen') that could
>> look at the screen, it is possible/likely a call to the add_effects
>> function would change the output of the function.
>> Benjamin Tolputt
>> Analyst Programmer
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