Études for Erlang

Étude 9-2: 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 deisre. 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 5-1 to allow either integer or float input.

Here is sample output. Due to Erlang’s asynchronous nature, the user prompts and logging are often interleaved in the most inconvenient places.

1> c(bank).
{ok,bank}
2> bank:account(2000).
D)eposit, W)ithdraw, B)alance, Q)uit: D
Amount to deposit: 300
Your new balance is 2300
D)eposit, W)ithdraw, B)alance, Q)uit:
=INFO REPORT==== 26-Jan-2013::06:42:52 ===
Successful deposit 300
W
Amount to withdraw: -200
Withdrawals may not be less than zero.
=ERROR REPORT==== 26-Jan-2013::06:42:56 ===
Negative withdrawal amount -200
D)eposit, W)ithdraw, ...