Études for Elixir

Chapter 10. Handling Errors

Étude 10-1: try and rescue

Update the stats module that you wrote in Étude 7-3 so that it will catch errors in the minimum/1, maximum/1, mean/1 and stdv/1 functions.

Here is some sample output.

iex(1)> c("stats.ex")
[Stats]
iex(2)> Stats.minimum([])
%MatchError{term: []}
iex(3)> Stats.mean([])
%ArithmeticError{}
iex(4)> Stats.mean([:one, :two])
%ArithmeticError{}
iex(5)> Stats.stdv([1])
%ArithmeticError{}

See a suggested solution in Appendix A.

Étude 10-2: Logging Errors

Write a module named Bank that contains a function account/1. The function takes a numeric balance, which gives the current balance in the account in imaginary dollars.

The function will repeatedly ask for a transaction (deposit, withdraw, balance inquiry, or quit). If a deposit or withdrawal, it asks for the amount to deposit or withdraw, and then does that transaction. If a deposit is more than $10,000, the deposit may be subject to hold.

Provide output to the customer, and also use error_logger to write to a log file (which, in this case, will go to your terminal). Choose any form of input prompts and feedback and logging messages that you desire. Handle the following situtations:

• Deposits and withdrawals cannot be negative numbers (error)
• Deposits of $10,000 or more might be subject to hold (warning)
• All other transactions are successful (informational)

Use get_number/1 from Étude 5-2 to allow either integer or float input; you may want to modify it to take the entire prompt as its argument. ...