Object-oriented programming¶
Simple type extension¶
Goal: work with type extensions using record types containing numeric components.
Steps:
Implement the
Type_Extensionspackage.
Declare the record type
T_Float.Declare the record type
T_MixedImplement the
Initfunction for theT_Floattype with a floating-point input parameter.Implement the
Initfunction for theT_Floattype with an integer input parameter.Implement the
Imagefunction for theT_Floattype.Implement the
Initfunction for theT_Mixedtype with a floating-point input parameter.Implement the
Initfunction for theT_Mixedtype with an integer input parameter.Implement the
Imagefunction for theT_Mixedtype.
Requirements:
Record type
T_Floatcontains the following component:
F, a floating-point type.Record type
T_Mixedis derived from theT_Floattype.
T_MixedextendsT_Floatwith the following component:
I, an integer component.Both components must be numerically synchronized:
For example, if the floating-point component contains the value 2.0, the value of the integer component must be 2.
In order to simplify the implementation, you can simply use
Integer (F)to convert a floating-point variableFto integer.Function
Initreturns an object of the corresponding type (T_FloatorT_Mixed).
For each type, two versions of
Initmust be declared:
one with a floating-point input parameter,
another with an integer input parameter.
The parameter to
Initis used to initialize the record components.Function
Imagereturns a string for the components of the record type.
In case of the
Imagefunction for theT_Floattype, the string must have the format"{ F => <float value> }".
For example, the call
Image (T_Float'(Init (8.0))))should return the string"{ F => 8.00000E+00 }".In case of the
Imagefunction for theT_Mixedtype, the string must have the format"{ F => <float value>, I => <integer value> }".
For example, the call
Image (T_Mixed'(Init (8.0))))should return the string"{ F => 8.00000E+00, I => 8 }".
Online Store¶
Goal: create an online store for the members of an association.
Steps:
Implement the
Online_Storepackage.
Declare the
Membertype.Declare the
Full_Membertype.Implement the
Get_Statusfunction for theMembertype.Implement the
Get_Pricefunction for theMembertype.Implement the
Get_Statusfunction for theFull_Membertype.Implement the
Get_Pricefunction for theFull_Membertype.Implement the
Online_Store.Testschild package.
Implement the
Simple_Testprocedure.
Requirements:
Package
Online_Storeimplements an online store application for the members of an association.
In this association, members can have one of the following status:
associate member, or
full member.
Function
Get_Pricereturns the correct price of an item.
Associate members must pay the full price when they buy items from the online store.
Full members can get a discount.
The discount rate can be different for each full member — depending on factors that are irrelevant for this exercise.
Package
Online_Storehas following types:
Percentagetype, which represents a percentage ranging from 0.0 to 1.0.
Membertype for associate members containing following components:
Start, which indicates the starting year of the membership.
This information is common for both associate and full members.
You can use the
Year_Numbertype from the standardAda.Calendarpackage for this component.
Full_Membertype for full members.
This type must extend the
Membertype above.It contains the following additional component:
Discount, which indicates the discount rate that the full member gets in the online store.
This component must be of
Percentagetype.For the
MemberandFull_Membertypes, you must implement the following functions:
Get_Status, which returns a string with the membership status.
The string must be
"Associate Member"or"Full Member", respectively.
Get_Price, which returns the adapted price of an item — indicating the actual due amount.
For example, for a full member with a 10% discount rate, the actual due amount of an item with a price of 100.00 is 90.00.
Associated members don't get a discount, so they always pay the full price.
Procedure
Simple_Test(from theOnline_Store.Testspackage) is used for testing.
Based on a list of members that bought on the online store and the corresponding full price of the item,
Simple_Testmust display information about each member and the actual due amount after discounts.Information about the members must be displayed in the following format:
Member # <number> Status: <status> Since: <year> Due Amount: <value> --------For this exercise,
Simple_Testmust use the following list:
#
Membership status
Start (year)
Discount
Full Price
1
Associate
2010
N/A
250.00
2
Full
1998
10.0 %
160.00
3
Full
1987
20.0 %
400.00
4
Associate
2013
N/A
110.00
In order to pass the tests, the information displayed by a call to
Simple_Testmust conform to the format described above.
You can find another example in the remarks below.
Remarks:
In previous labs, we could have implemented a simplified version of the system described above by simply using an enumeration type to specify the membership status. For example:
type Member_Status is (Associate_Member, Full_Member);
In this case, the
Get_Pricefunction would then evaluate the membership status and adapt the item price — assuming a fixed discount rate for all full members. This could be the corresponding function declaration:type Amount is delta 10.0**(-2) digits 10; function Get_Price (M : Member_Status; P : Amount) return Amount;In this exercise, however, we'll use type extension to represent the membership status in our application.
For the procedure
Simple_Test, let's consider the following list of members as an example:
#
Membership status
Start (year)
Discount
Full Price
1
Associate
2002
N/A
100.00
2
Full
2005
10.0 %
100.00
For this list, the test procedure displays the following information (in this exact format):
Member # 1 Status: Associate Member Since: 2002 Due Amount: 100.00 -------- Member # 2 Status: Full Member Since: 2005 Due Amount: 90.00 --------Here, although both members had the same full price (as indicated by the last column), member #2 gets a reduced due amount of 90.00 because of the full membership status.