RPN Calculator Output
10 Points
try-rescue-else-after
dynamic-dispatch
Instructions
Work is progressing well at Instruments of Texas on the RPN Calculator. Your team now wants to be able to write a string version of the equation to an IO resource.
1. Open a file
Your team hasn't decided what type of device to write the equation to, so you suggest using a dynamic dispatch approach to be able to inject the resource into the function rather than hard-code it in. Implement the write/3 function to open an IO device using the resource and the filename.
You can assume resource will always be an atom that represents a module which has an open/1 function that returns {:ok, io_device}.
When the function succeeds, return an ok-tuple with the equation.
RPNCalculator.Output.write(resource, "file_to_be_written", "1 4 +")
# {:ok, "1 4 +"}2. Attempt to write to the IO device
Now that you've opened the IO device, attempt to write to it using IO.write/2.
Extend the write/3 function to perform this action. The write action attempt may raise an error, rescue from the error returning an error-tuple:
RPNCalculator.Output.write(resource, "bad_file", "1 4 +")
# {:error, "Unable to write to resource"}3. Close the IO device
It is a good practice to always try to release resources that you have opened, even if the function using the resource raises an error. Extend the write/3 function to call the resource's close function to close the IO device.
You can assume resource will always be an atom that represents a module which has a close/1 function which takes an IO device.
RPN Calculator Output
10 Points
try-rescue-else-after
dynamic-dispatch
Instructions
Work is progressing well at Instruments of Texas on the RPN Calculator. Your team now wants to be able to write a string version of the equation to an IO resource.
1. Open a file
Your team hasn't decided what type of device to write the equation to, so you suggest using a dynamic dispatch approach to be able to inject the resource into the function rather than hard-code it in. Implement the write/3 function to open an IO device using the resource and the filename.
You can assume resource will always be an atom that represents a module which has an open/1 function that returns {:ok, io_device}.
When the function succeeds, return an ok-tuple with the equation.
RPNCalculator.Output.write(resource, "file_to_be_written", "1 4 +")
# {:ok, "1 4 +"}2. Attempt to write to the IO device
Now that you've opened the IO device, attempt to write to it using IO.write/2.
Extend the write/3 function to perform this action. The write action attempt may raise an error, rescue from the error returning an error-tuple:
RPNCalculator.Output.write(resource, "bad_file", "1 4 +")
# {:error, "Unable to write to resource"}3. Close the IO device
It is a good practice to always try to release resources that you have opened, even if the function using the resource raises an error. Extend the write/3 function to call the resource's close function to close the IO device.
You can assume resource will always be an atom that represents a module which has a close/1 function which takes an IO device.