1. Robo – Software Engineering
…software engineering example exercise
...
David Davenport
Computer Eng. Dept.,
Bilkent University Ankara - Turkey.

2. House Problem
Who has attempted it?

3. Robo – House Problem (1) Specify pieces & order roof main Pre-cond.
Post-cond.
main
roof 2 1
250x250x250
50x50
100x50
250
Break problem into few natural pieces, specify sequence, specify sizes, specify pre & post-conditions.
Ask: do these pieces done in this order produce the required solution? Yes, proceed. No, try again!
Ask: Could you “subcontract” each piece? Is there sufficient information to produce that piece (without knowledge of any other piece or the problem), such that if done correctly (i.e. to your specifications) then it must (is guaranteed) to fit into your solution.
Note: missing dimensions means that if the roof is sub-contracted it may be too big or too small to fit our house!
Can use equtri for roof, so just need to think about main only.

4. Robo – House Problem (2) Then solve pieces… window door main walls
Pre-cond.
Post-cond.
walls
window
door
150x25
movetoleftwin
150
movetorightwin
150x75
movetodoor 7 1 3 2 4 6 5
main
NOTE: This is not correct. It does not solve the given problem! WHY? Post condition is not met. FIX.
Can reuse rect method for walls, door & windows.
? Can we generate a general move method to handle all these cases ?
Notice… so far no Robo code, only design on paper.
IMPORTANT: Design then implementation, not the reverse!
When implementing… do each piece separately & test the unit (unit testing) before integrating.
Hint: make special markstart & markend methods to indicate pre/post-conditions during testing/debugging.
d walls
d movetoleftwin
d window
d movetorightwin
d movetodoor
d door
d movetoendpoint
main

5. Software
Engineering
Exercise
Form teams, implement, then reflect!

6. Basic Pieces… topright movetoleft base toprightbottom diamond topleft
Pre-cond.
Post-cond.
Basic Pieces…
(2a + b)
topright
(2a + 2b)
movetoleft
(2a + 2b)
base
(a)
toprightbottom
(b)
(2b)
(a)
diamond 45
(a)
topleft
Note: names are deliberately vague in order not to give the game away!
(b)
(a)
moveup
(a)
movedown
(a)
side
(a)
lefttop

7. Composite Pieces… bc ( a, b) slice ( a, b, c) slicetop ( a, b)
d side( b) x a slice( b, 12, 10) d side( b)
bc ( a, b)
d base( b, c)
d moveup( a)
d slicetop( b, c)
d movedown( a)
slice ( a, b, c)
Note: names are deliberately vague in order not to give the game away!
d movetoleft( a, b) d topleft( b) d holder( 100, a, a) d topright( a, b)
slicetop ( a, b)
d lefttop( a, b) d diamond( c) d toprightbottom( a, b)
holder ( a, b, c)

8. Software
Engineering
Exercise
The overall design!

9. Birthday Cake Design Game’s up!
Of course, now we need sizes (in terms of parameters) plus pre & post conditions, etc.
Maybe describe in english… beginnings of algorithms?

10. Birthday Cake Design 1 2 3 tofirstcandle // birthdaycake
d Rect(200,450) //cake body
d tofirstcandle
d candles

11. To First Candle tofirstcandle // tofirstcandle p f(200) r(90) f(50)

12. Candles
// candles
x 4 candle

13. Candle 1 2 3 4 // candle // candlebodytoflame // flametonextcandle
d Rect(200,50) // candle body
d candlebodytoflame
d Rect(40,40) // candle flame
d flametonextcandle
Candle 1 2 3 4
// candlebodytoflame p
f(200)
r(90)
f(25)
l(135)
// flametonextcandle p
r(135)
f(25)
r(90)
f(200)
l(90)
f(50)

14. SUMMARY
Advantages of TDSD
The TDSD methodology

15. Relating Design & Code Big problems -> lots of pieces!
Difficult to understand & track
relation of pieces to each other
& between pieces of design & code
Pieces of design numbered 1, 2, 3…
Number sub-pieces 1.1, 1.2… & 2.1, 2.2…
Methods require naming pieces in design
Include piece numbers in code too.

16. The TDSD Methodology Understand the problem requirements
Break into natural pieces, making sure to fully specify them and the order in which they are to be done
Check whether these pieces done in this sequence solve the problem
If no, revise & recheck until you have a set & order that do correctly solve it!
If/when yes… repeat process with any non-trivial sub-pieces and so on until you only have trivial pieces!
Finally, implement & test each of them separately, then integrate & test whole!

17. Tips…
Have you FULLY specified ALL the sub-pieces? and exactly how they fit together?
Sub-contracting
Have you described the sub-problem in sufficient detail that someone would be able to solve it without any additional knowledge of the original problem?
Don’t be afraid to revise solutions or even scrap them entirely. It is not always possible to find best solution first time!
Don’t start to solve sub-problems until you are absolutely sure that the your proposed solution is correct. Doing so may waste time & effort.
Must go from BIG to small -not small to big!!
Your solutions must demonstrate you understand top-down design –require at least 2 or 3 levels
Robo limited to 20 line methods
This must include comments!
So ~10 comments + 10 commands (max, remember )

18. Advantages of TDSD Small pieces easier to solve correctly!
Projects easier to manage
divides work naturally
Projects can be completed quicker
easıer to reuse pieces
pieces can be done simultaneously
Projects done in secrecy
workers don’t see big picture
Testing & integration is simplified

19. Summary You should have learnt about & understand the rationale for…
Comments
White space
Meaningfully named methods
Method parameters
Pre & post conditions
Repetition
Top down structured design!
Happy programming ...BYE

21. (a)
100x100
base
Library pieces! 3 2 1