AssignmentFinal #36
AssignmentFinal #36
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| send from, { :next_is, value} | ||
| counter(value+1) | ||
| end | ||
| end |
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-2 layout
It really is important. I know it sounds trivial, but nice looking code is well maintained code.
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| defmodule Ex02 do | |||
| def new_counter(value) do | |||
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0
this really doesn't work. You're supposed to be storing the value in a single agent, and then updating that value on each call to next_value. Instead, you're keeping the count in the client code, and this code is just a complicated way of adding 1.
Here's what I'd like to see:
def new_counter(initial_value \\ 0) do
{ :ok, agent } = Agent.start_link(fn -> initial_value end)
agent
end
def next_value(agent) do
Agent.get_and_update(agent, &{ &1, &1 + 1})
end| # assert value == 1 | ||
| # end | ||
| test "counter using an agent" do | ||
| { :ok, counter } = Agent.start(fn -> 0 end) |
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-5
This is just setting the value of zero into an agent.
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| end | ||
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| def new_global_counter do |
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-5
This code contains a race condition. Because you do the get and update as two separate calls, it is possible for two processes accessing this agent to both get the same value.
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| #Ref - Programming Elixir Book | |||
46884868
Rahul Khandalkar