Learning a language --- a labour for the masses!

Tools supplementing knowledge on libraries:

Hoogle, Hayoo:

on-line dictionaries for Haskell libraries

Tools supplementing knowledge on libraries:

Library browsers of IDEs and editors (Leksah)

Tools supplementing knowledge on libraries:

Library browsers of IDEs and editors (App Inventor)

Tools supplementing knowledge on libraries:

Auto-completion (GHCi)

Tools supplementing knowledge on libraries:

Automatic programming from examples

(Flash Fill of Excel 2013)

Tools supplementing knowledge on libraries:

MagicHaskeller on the Web (this presentation)

Supported browsers: Konqueror

Supported browsers: Firefox

Supported browsers: W3m (terminal-based)

Supported browsers: Emacs-W3m (Emacs-based)

Supported browsers: Chrome

Supported browsers: Internet Explorer

Supported browsers: Safari on iOS

Supported browsers: Android Web Browser

Feel free to try it from your PC / smart phone!

Introductory Examples

• replicating the elements of a list given number of times.
• returning the second last element of a list.
• higher-order functions.

Implementation

Current Limitations

• pure total functions only. IO ⊥

• limited set of available functions
  • subset of Prelude, Data.List, Data.Char, Data.Maybe
  • Float Double Integer

• up to 7 function applications in the internal representation

• only a few literals

Evaluation

• Problems 1-20 from 99 Haskell Problems

• Examples 1-10 from the Flash Fill paper (Gulwani, PoPL 2011)

Number of solved instances.

problems	MagicHaskeller	Flash Fill
99 Haskell Problems	11/20 (55%)	3/20 (15%)
Flash Fill Examples	3/10 (30%)	9/10 (90%)

Discussion

Flash Fill is quite specialized

• DSL

• limited use of conditionals

• powerful regexp, but

• can only deal with strings. no arithmetic

What we want to solve

Summary

• Haskell program synthesis by examples

• Sometimes works, sometimes not.

• Supposed to be useful for casual programming

• Generate-and-test approach with shared memo table

Future work

• Lots of room for efficiency/usability improvements

• MagicExceller (?)

  • non-string functions
  • readable programs (using Excel functions instead of DSL)

• The idea of shared memo table might be applied to Agda proof search.

... and (missed) Past work

• Regrettably I did not check 2013 Programming Contest.

Thanks

for not cracking the server so far!

Appendix

Before Pointing the Alternative Server to you

Please wait while I am checking if the usual server is really stopped, using this:

• If the server is actually running, go to this page.
• If the server is down, just go to the next page.

The Alternative Server

• before pointing the alternative server to you,
  • I will check if the usual server is really stopped, if I haven't.
  • If you think that your query may have caused the server down,
    PLEASE DO NOT TRY THE SAME QUERY AGAIN TO THE ALTERNATIVE SERVER!
    I will analyze the log to identify the query, and use the information for fix the server.
• The alternative server is http://nautilus.cs.miyazaki-u.ac.jp/cgi-bin/MagicHaskeller-exp.cgi. (Just add "-exp" to the usual CGI address, if you have already accessed it.)

If the Server is Actually Running,

please press the Back button of your browser and try a different query.
For further information, check the 5th item of "Limitations, ToDos, and Future Plans" of the homepage of MagicHaskeller

Evaluation: 99 Haskell Problems

Problem 1: Find the last element of a list.

Problem 2: Find the last but one element of a list.

Problem 3: Find the K'th element of a list. The first element in the list is number 1.

Problem 4: Find the number of elements of a list.

Problem 5: Reverse a list.

Problem 6: Find out whether a list is a palindrome.

Problem 7: Flatten a nested list structure. Could not make a query (no support of creating new data types)

Problem 8: Eliminate consecutive duplicates of list elements.

Problem 9: Pack consecutive duplicates of list elements into sublists.

Problem 10: Run-length encoding of a list.

Problem 11 - 13: Could not make a query (no support of creating new data types)

Problem 14: Duplicate the elements of a list.

Problem 15: Replicate the elements of a list a given number of times.

Problem 16: Drop every N'th element from a list.

Problem 17: Split a list into two parts; the length of the first part is given.

Problem 18: Extract a slice from a list.

Problem 19: Rotate a list N places to the left.

Problem 20: Remove the K'th element from a list.

Evaluation: Problems from the Flash Fill paper (Gulwani, PoPL 2011)

Example 1: Extract the telephone number.

Example 2: Extract the quantity.

Example 3: Extract the directory name

Example 4: Generate abbreviation.

Example 5: Split odds.

Example 6: Remove excess spaces.

Results in Full

99 Haskell Problems

problem	MagH result	Flash Fill result
Problem 1	O	O
Problem 2	O	O
Problem 3	O	X
Problem 4	Otr	X
Problem 5	Otr	X
Problem 6	O	X
Problem 7	Xdata	Xdata
Problem 8	O	X
Problem 9	Otr	X
Problem 10	X	X
Problem 11	Xdata	Xdata
Problem 12	Xdata	Xdata
Problem 13	Xdata	Xdata
Problem 14	O	O
Problem 15	O	X
Problem 16	X	X
Problem 17	X	X
Problem 18	O	X
Problem 19	X	X
Problem 20	X	X

Flash Fill Examples

problem	MagH result	Flash Fill result
Example 1	X	O
Example 2	O	O
Example 3	X	O
Example 4	O	O
Example 5	X	O
Example 6	O	O
Example 7	X	O
Example 8	X	X
Example 9	X	O
Example 10	X	O