SECTION(6, Tutorial 6)
m5_question(BO(Question 6.1:) Study, compile and run the following code.
Note the use of the EM(class variable) TT(myMoney). A class
variable is different from a variable that is local to a function
because the lifetime of the class variable is for the duration that
the program is run, whereas the lifetime of a local variable is for
the duration of the function call. In the code that follows, the
variable TT(myMoney) is used to store a numerical value, for how
much money you have.
m4_begin_indent
NU()CLASS CLSS(Money) EOL
BEGIN EOL
PD SCOM(/** Property myMoney stores money value in dollars */) EOL
PD CLASS_VAR INT myMoney; EOL
EOL
PD FUNCTION VOID FUNC(spend)(STRING VARI(item), INT VARI(value)) EOL
PD BEGIN EOL
PD PD myMoney = myMoney - value; EOL
PD PD SYSTEM_OUT_PRINTLN(STRI("*** spent DOLLAR") + EOL
PD PD PD PD PD PD PD PD value + EOL
PD PD PD PD PD PD PD PD STRI(" on ") + item + EOL
PD PD PD PD PD PD PD PD STRI("COMMA() leaving you with DOLLAR") + myMoney); EOL
PD PD END EOL
PD END EOL
PD BEGIN_MAIN EOL
PD PD myMoney = 100; EOL
PD PD spend(STRI("aquarium"),NUMB(50)); EOL
PD PD spend(STRI("shoes"),NUMB(100)); EOL
PD PD spend(STRI("lipstick"),NUMB(20)); EOL
PD END_MAIN EOL
END EOL
m4_end_indent
)
m5_question(BO(Question 6.2:) Change the TT(myMoney) class variable
so that it is a EM(double) (short for double-precision floating point)
rather than an EM(int). You will need to add a new function
TT(money2string) that converts double values into strings. For example
the floating point number 1.2345 should be printed out as
DOLLAR()1.23. If TT(x) is a double then the following expression
converts TT(x) from a double into a number of dollars TT((INT)x) and
the following expression converts TT(x) into a number of cents
TT((int)(money * 100) - 100 * dollars). Note that you will need to
make it so that DOLLAR(1.03) prints out as this value.)
m5_question(BO(Question 6.3:) Add an EM(if) statement to the
TT(spend) function so that it uses SYSTEM_OUT_PRINTLN to print out an
error message if the person does not have enough funds in their bank
account to pay for the item parameter.)
m5_question(BO(Question 6.4:) Add a new class variable TT(double governmentsMoney)
and make it so that 12.5% of the cost of each item goes to the
government in the form of GST.)
m5_question(BO(Question 6.5:) Add a new class variable
TT(numBattleships) that records how many batteships are owned by the
government. Write a function TT(buyBattleShips) that causes the
government to buy as many battleships as it can afford. Make it so
that the TT(buyBattleShips) function prints out how many battleships
were purchased. Let the cost of each battleship be one million
dollars and store this value in a variable called TT(costOfShip).
Please note that if the government's money is less the one million
dollars then no battleships will be purchased.)
m5_question(BO(Question 6.6:) Set the initial value for
TT(governmentsMoney) to be two millions dollars, then call the
TT(buyBattleShips) function and verify that two battleships were
purchased.)
