Lisp Project #2,  The Bank

Write a Lisp program that interprets an input file detailing the creation of bank accounts, withdrawals and deposits to and from those accounts, and printing of the balances of accounts.  The data of each account should be stored in a structure.  The structures should be organized into an association list, keyed by the account owner's name.

You must provide a function named MAIN, which takes a single argument, the name of the input file.

For extra credit (a full grade increase to any programming assignment), store the data not in an association list, but in a binary search tree, sorted by the account owner's name.
  Additional extra credit (a half grade increase to any programming assignment) will be awarded to any program not using any global variables, but one, the association list of accounts.
 

The input file:

• new name initial-balance:  Opens a new bank account, where name is a single symbol, the name of the owner of the account. initial-balance is a number, the amount of money initially in the account.  The function should print the message: "Account opened for name in the amount of initial-balance."
• draw name amount:  Attempts to make a withdrawl from the account belonging to name.  If no such account exists, print "No account exists for an owner named name."  If the withdrawl amount exceeds the current balance in that account, print "Insufficient funds to withdrawl amount from name's account.  Current balance is current-balance", where current-balance is the amount of money currently in that account.  In all other cases, debit the appropriate account by the given amount, and print the message: "Account for name is debitted amount, leaving a balance of current-balance."
• deposit name amount: If there is an account belonging to name, credit the account by amount, and print "Account for name is creditted amount, leaving a balance of current-balance."  If there is no such account, print the message, "No account exists for an owner named name."
• print name:  If there is an account belonging to name, print "The account belonging to name currently has a balance of current-balance.  The transactions on this account are", and then a series of indented lines, each line of the form, "DEPOSIT amount balance" or "DEBIT amount balance", where balance was the balance of the account just after the corresponding transaction was completed.  The transactions should be listed from oldest (top) to most recent (bottom).
• printall s-expression: s-expression will be a single s-expression that evaluates to T or NIL.  The s-expression will contain the symbols NAME and BALANCE.  Your program should evaluate the s-expression on each account currently in the system, giving NAME the name of the account (a string), and BALANCE, the curernt balance of that account.  For each account for which the s-expression does not evaluate to NIL, the program should print "The account name with balance current-balance satisfies the given s-expression."

Lisp you will need:

You might also want to use FORMAT, to generated formatted output for your tables.

Recommended course of action:

Write a simple version of MAIN that simply opens the file of the given name, and reads the contents of the file, one symbol at a time, printing those symbols.  For example, say I created a file "D:/Matt/test.txt" containing:

new bob 100
deposit bob 150

then called (main "D:/Matt/test.txt"), this should generate the output:

NEW
BOB
100
DEPOSIT
BOB
150

Next, try implementing the system using an association list.  There is info on association lists on CMU's on-line version of ClTl2.  The key operators with association lists (or "a-lists") are ACONS and ASSOC.  Here is a simple explanation of their workings:

acons key datum a-list
acons constructs a new association list by adding the pair (key . datum) to the old a-list.

assoc item a-list &key :test :test-not :key
assoc-if predicate a-list
assoc-if-not predicate a-list
Each of these searches the association list a-list. The value is the first pair in the a-list such that the car of
the pair satisfies the test, or nil if there is no such pair in the a-list.

You'll want to keep the transactions for each account in a list, probably, to facilitate the PRINT operator.

Sample Input

Sample Output

The account belonging to BOB currently has a balance of $180.
  The transactions on this account are:

  Trans     Amt   Bal
  DEPOSIT   100   100
  DEPOSIT   150   250
  DEBIT      70   180
 

Account opened for EMMA in the amount of $400.
The following accounts satisfy the given s-expression, (> BALANCE 199):
  EMMA, SUE, TOM

Account for BOB is creditted $100, leaving a balance of $280.
The following accounts satisfy the given s-expression,
(AND (> BALANCE 199) (STRING< NAME "PPP")):
  EMMA, BOB