CSC151.02 2010S Functional Problem Solving : Labs
Primary: [Front Door] [Schedule] - [Academic Honesty] [Instructions]
Current: [Outline] [EBoard] [Reading] [Lab] - [Assignment]
Groupings: [Assignments] [EBoards] [Examples] [Exams] [Handouts] [Labs] [Outlines] [Projects] [Readings]
References: [A-Z] [By Topic] - [Scheme Report (R5RS)] [R6RS] [TSPL4]
Related Courses: [CSC151.01 2010S (Weinman)] [CSC151 2009F (Rebelsky)]
Misc: [SamR] [MediaScript] [GIMP]
Summary: In this lab, we consider techniques for building objects, collections of data that support operations on those data.
a. Make a copy of the make-switch
procedure from
the reading.
b. Test the switches created by the make-switch
procedure. Here are a few possible instructions.
>
(define lamp-switch (make-switch))
>
(define vacuum-cleaner-switch (make-switch))
>
(lamp-switch ':get-position)
>
(vacuum-cleaner-switch ':get-position)
>
(lamp-switch ':toggle!)
>
(lamp-switch ':get-position)
>
(vacuum-cleaner-switch ':get-position)
>
(lamp-switch ':toggle!)
>
(vacuum-cleaner-switch ':toggle!)
>
(lamp-switch ':get-position)
>
(vacuum-cleaner-switch ':get-position)
As you may know, some switches have more than two positions. For example, we might have a switch that switches between the values 0, 1, 2, and 3. (For a two-way light, 0 might represent “off”, 1 might represent “light one on”, 2 might represent “light two on”, and 3 might represent “both lights on”.) In general, you can only toggle to the next higher value (with 3 returning to 0 when toggled).
Implement a four-stage-switch
object that responds to the
same messages as a switch, but with four possible stages.
Define a one-field object, tally
, that responds
to exactly four messages:
':get-value
,
':set-contents-to-zero!
,
':increment!
, which has the effect of increasing the
number stored in the contents
field by 1.
':decrement!
, which has the effect of decreasing the
number stored in the contents
field by 1.
The initial value of the tally should be 0.
Note that you are creating a single object, not a procedure that creates objects.
For example,
>
(tally ':get-value)
0
>
(tally ':increment!)
>
(tally ':get-value)
1
>
(tally ':decrement!)
>
(tally ':decrement!)
>
(tally ':decrement!)
>
(tally ':get-value)
-2
a. Define a make-tally
procedure that constructs and returns
objects similar to the tally
object you defined in the
previous exercise.
b. Create two tally objects and demonstrate that they can be incremented and reset independently.
Write a new make-tally
procedure that allows the client
to create new tallys with a specied initial value. For example, a
professor might say that a starting grade is 90 with
>
(define grade (make-tally 90))
The professor would then increment and decrement it as students do good or bad work.
a. Define a constructor procedure, make-monitored-tally
, for
objects similar to the tally
objects from above,
except that each such object keeps track of the total
number of messages that it has received.
Hint: For this exercise, you may want to make two vectors, one for the value of the tally and one for the count of operations. Alternately, you could make a two-element vector in which element 0 of that vector is the value of the tally and element 1 of that vector is the count of operations.
b. Test your procedure.
Primary: [Front Door] [Schedule] - [Academic Honesty] [Instructions]
Current: [Outline] [EBoard] [Reading] [Lab] - [Assignment]
Groupings: [Assignments] [EBoards] [Examples] [Exams] [Handouts] [Labs] [Outlines] [Projects] [Readings]
References: [A-Z] [By Topic] - [Scheme Report (R5RS)] [R6RS] [TSPL4]
Related Courses: [CSC151.01 2010S (Weinman)] [CSC151 2009F (Rebelsky)]
Misc: [SamR] [MediaScript] [GIMP]
Copyright (c) 2007-10 Janet Davis, Matthew Kluber, Samuel A. Rebelsky, and Jerod Weinman. (Selected materials copyright by John David Stone and Henry Walker and used by permission.)
This material is based upon work partially supported by the National Science Foundation under Grant No. CCLI-0633090. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
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