1. Spreadsheets are code
Felienne Hermans (@felienne)

2. Spreadsheets are code
Felienne Hermans (@felienne)
In this slidedeck I explain whyy
spreadsheets are code, and what
we can do with that idea.

3. Spreadsheets are mislabeled

4. Spreadsheets are mislabeled
People often think of spreadsheets
as data, but...

5. Spreadsheets are code

6. Spreadsheets are code
I have made it my life’s work to
spread the happy word
“Spreadsheets are code!”

7. Spreadsheets are code
I have made it my life’s work to
spread the happy word
“Spreadsheets are code!”
If you don’t immediately believe
me, I have three reasons*
* If you do believe me, skip the next 10 slides ;)

8. 1) Used for similar problems

9. This tool (for stock price
computation) could have been
built in any language. C,
JavaScript, COBOL, or Excel.
The problems Excel is used for are
often (not always) similar to
problems solved in different
languages.

10. 2) Formulas are Turing complete

11. 2) Formulas are Turing complete
I go to great lengths to make my
point. To such great lengths that I
built a Turing machine in Excel,
using formulas only.

12. Here you see it in action. Every row
is an consecutive step of the lint.
This makes it, in addition to a proof
that formulas are Turing complete,
Also a nice visualization of a Turing
machine.

13. 3) They suffer from the same problems

14. 3) They suffer from the same problems

15. 3) They suffer from the same problems

16. 3) They suffer from the same problems

17. In summary: both the activities,
complexity and problems are the same

18. So if spreadsheets are code, can we
apply software engineering methods?

20. In software, tools have been created to
help programmers understand code

22. Speadsheets however, lack support
for testing, refactoring and code
analysis.

23. My goals is to bring those tools to
spreadsheets

24. In my dissertation, I defined smells
for spreadsheet formulas

25. www.felienne.com/publications
In my dissertation, I defined smells
for spreadsheet formulas

26. If you say smells

27. If you say smells, you say refactoring

28. So, we built BumbleBee:
a refactoring tool for spreadsheets

29. So, we built BumbleBee:
a refactoring tool for spreadsheets

39. You can download BumbleBee from
my website (felienne.com/BumbleBee)

40. The transformations are entirely
programmable, with a small language

41. And of course, if you say refactoring,
you say …

42. And of course, if you say refactoring,
you say testing

43. Spreadsheets tests are hiding in plain
sight

45. These test formulas are common,
and they can be exploited

46. Our tool Expector can find test formulas

52. Expector helps users to understand
robustness of their spreadsheets

53. Also available:
felienne.com/Expector

54. Thanks for viewing the slides for
Spreadsheets: are code!
Want to know more?
• Visit my sites
 felienne.com
 spreadsheetlab.org
• Send a tweet
 @felienne
• Send an email
mail@felienne.com