Reusing Code example: Class Quadrilateral

1
Reusing Code example Class Quadrilateral

• Consider a class to represent quadrilaterals,
  i.e. polygons with four sides, and
• That people are by nature lazy (which for us
  means that wed like to reuse code).
• A quadrilateral is defined by its four vertices,
  which are of course Points (we include a char
  that is used as a label
• class Quad
• public
• char label
• Point vert

• int main()
• // Create quadrilateral S
• Quad S
• S.vert new point4
• // Read label and vertices
• cout ltlt "Enter label and 4 vertices "
• cin gtgt S.label
• for(int i 0 i lt 4 i)
• cin gtgt S.verti
• // Write label and vertices
• cout ltlt "Your quadrilateral is " ltlt S.label ltlt
  " "
• for(int j 0 j lt 4 j)
• cout ltlt S.vertj ltlt ' '
• cout ltlt endl
• return 0

2
Header files and Definition (.cpp) files

• // in file Point.h
• include ltiostreamgt
• include ltfstreamgt
• using namespace std
• class point
• public
• double x, y
• void read(point p, istream IN)
• void write(point p, ostream OUT)
• point operator(point a, point b)
• point operator/(point P, double z)
• ostream operatorltlt(ostream OUT, point p)
• istream operatorgtgt(istream IN, point p)

• // in file Point.cpp
• include Point.h
• void read(point p, istream IN)
• char c
• IN gtgt c gtgt p.x gtgt c gtgt p.y gtgt c
• point operator(point a, point b)
• point S
• S.x a.x b.x
• S.y a.y b.y
• return S
• istream operatorgtgt(istream IN, point p)
• read(p,IN)
• return IN

3
main() that includes point.h

• A .h file (or header file) tells how to use the
  module, and
• a .cpp file that contains the source code that
  implements the module (i.e. that tells the
  compiler how all these functions really work).
• include "point.h"
• class Quad
• public
• char label
• point vert

• int main()
• // Create quadrilateral S
• Quad S
• S.vert new point4
• // Read label and vertices
• cout ltlt "Enter label and 4 vertices "
• cin gtgt S.label
• for(int i 0 i lt 4 i)
• cin gtgt S.verti
• // Write label and vertices
• cout ltlt "Your quadrilateral is " ltlt S.label ltlt
  " "
• for(int j 0 j lt 4 j)
• cout ltlt S.vertj ltlt ' '
• cout ltlt endl
• return 0

4
Static Arrays

• We've seen dynamic arrays, where the size of the
  array can change from run to run of the program.
• Ship shipsAtSeaArray new ShipN // where
  user enters value for N
• Useful if the size of the array may need to
  change from run to run of a program.
• A static array s size is determined at compile
  time, so from run to run, the array's size is
  always the same
• int daysOfTheWeek7 // always 7 days in a
  week!
• Can initialize static arrays with values in s
• int prime10 2,3,5,7,11,13,17,19,23,29

5
Reconsider Class Quad

• class Quad
• public
• char label
• Point vert4 // static
  

• class Quad
• public
• char label
• Point vert // dynamic

6
Comparing static and dynamic arrays

• include "point.h"
• class Quad
• // identical other than vert
• public
• char label
• point vert4
• int main()
• // Create quadrilateral S
• Quad S
• // Read label and vertices
• cout ltlt "Enter lbl and 4 vertices"
• cin gtgt S.label
• for(int i 0 i lt 4 i)
• cin gtgt S.verti

• include "point.h"
• class Quad
• public
• char label
• point vert
• int main()
• // Create quadrilateral S
• Quad S
• S.vert new point4
• // Read label and vertices
• cout ltlt "Enter lbl and 4 vertices"
• cin gtgt S.label
• for(int i 0 i lt 4 i)

7
Tracking Cockroaches revisited

• Break the following program up into separate
  modules
• The Point" module
• Point.h and Point.cpp.
• The Hhmmss" module
• Hhmmss.h and Hhmmss.cpp.
• And the "main program" main.cpp which includes
  class Datum.

8
Classes Point, Hhmmss, and Datum

• class Point
• public
• double x, y
• void read(Point p, istream IN)
• void write(Point p, ostream OUT)
• //--- TIME IN HHMMSS
• class Hhmmss
• public
• int h,m,s
• void read(Hhmmss T, istream IN)

• //--- A DATA READING FROM THE EXPERIMENT ----//
• class Datum
• public
• Point position
• Hhmmss time
• void read(DatumD, istream IN)
• Note an instance of Datum is composed of a Point
  and a Hhmmss instance

9
The main() program

• int main()
• int N string s
• ifstream IN("trial.txt")
• IN gtgt N gtgt s gtgt s
• // Read and store data readings
• Datum A new DatumN
• for(int i 0 i lt N i)
• read(Ai,IN)
• // Get query time from the user
• Hhmmss T
• cout ltlt "Enter a time "
• read(T,cin)
• / Find 1st sighting at or after given time /
• int k 0
• while (k lt N Ak.time lt T)
• k

• if (k 0)
• cout ltlt "This was before the first sighting
  at "
• write(A0.position,cout)
• else if (k N)
• cout ltlt "This was after the last sighting at
  "
• write(AN-1.position,cout)
• else
• cout ltlt "The roach was somewhere between "
• write(Ak-1.position,cout)
• cout ltlt " and "
• write(Ak.position,cout)
• cout ltlt endl
• return 0

10
Function Definitions

• void read(Point p, istream IN)
• char c
• IN gtgt c gtgt p.x gtgt c gtgt p.y gtgt c
• void write(Point p, ostream OUT)
• OUT ltlt '(' ltlt p.x ltlt ',' ltlt p.y ltlt ')'
• void read(Hhmmss T, istream IN)
• char c
• IN gtgt c gtgt T.h gtgt c gtgt T.m gtgt c gtgt T.s gtgt c

• void read(Datum D, istream IN)
• char c
• IN gtgt c
• read(D.time,IN)
• IN gtgt c
• read(D.position,IN)
• IN gtgt c

11
ICE Converting Dates

• Write a program that reads a date in mm/dd/yyyy
  format and prints it out in "dd monthName yyyy"
  format. Make use of a static array for
  monthNames
• For example, entering
• 8/9/1961
• results in
• 9 August 1961
• Recall that a static array can be initialized
  with a list of values in 's.
• For example, an array of the first 10 prime
  numbers can be constructed like this
• int prime10 2,3,5,7,11,13,17,19,23,29

12
ICE Solution Converting Dates

• include ltiostreamgt
• include ltstringgt
• int main()
• // Create an array containing the month names
• string Month12 "January", "February",
  "March", "April",
• "May", "June", "July", "August",
  "September",
• "October", "November", "December"
• // Read date
• int m, d, y
• char c
• cin gtgt m gtgt c gtgt d gtgt c gtgt y
• // Write date
• cout ltlt d ltlt ' ' ltlt Monthm - 1 ltlt ' ' ltlt y ltlt
  endl
• return 0