Tuesday, 24 November 2015

The crossword that counts itself

I love puzzles. This is described by Alex Bellos at the Guardian.

It helps to write a spreadsheet to solve this.

  1. Set the column widths to be about the same as the height, making them look square.
  2. Draw out the puzzle by highlighting a phrase (there are 12 "phrases"), and formatting: format cells, borders, click outline, OK.
  3. Repeat for each of the other 11 phrases, highlight, Ctrl-Y (repeats the last format command for a new area)
  4. Count the lengths of the rectangles (these are "phrase length"), subtract (3 or 2) to get "word length"
  5. The area inside the blue box is named "puzzle"
  6. The formula (row 20) for "actual" is: = SUMPRODUCT( LEN(puzzle) - LEN( SUBSTITUTE(puzzle,"e","") ))
  7. This formula is copied for the 11 rows below and the letter edited, each time.
  8. The formula for "= target" is: =IF( E20 = F20, "Y", "N")
  9. When they all show "Y", the puzzle is solved.
  10. The sum in cell e32 just tallies the 12 "actual" numbers. It must eventually show 68 when the puzzle is solved
  11. The working between p18 : ae32 allows one to count the number of times each number word is used and tally them (must be = 68 too)
  12. The cells bordered in red are named: number
  13. The "word cells" formula is just: = number * R19
  14. This formula is copied down and across (to the 3 combos). The "3 combos" show the 3 possible combinations of possible words.
  15. The "# letters" fomula is just the length of the number. e.g.: = LEN( AD20 )

This is not so easy to solve using purely coded program, because the rules to narrow down the combinations are not so clear. After you've figured out what constraints must be met it, no doubt, becomes much easier to program.

Tuesday, 10 November 2015

Code spippets - Fsharp

GistBox Clipper

Clipper is the companion Chrome extension to GistBox. It allows users to create Gists from:

  • Example code blocks
  • Highlighted text
  • Any page on the web
Install Chrome Extension
http://www.gistboxapp.com/clipper-tutorial/
Enter keyboard data, via console, with validation.
/// Read a valid age (between 0 and 150) from key input let readage (person: string) = let mutable continueLooping = true let mutable age = 0 while continueLooping do Console.WriteLine("Enter {0}'s age (between 0 and 150): ", person) let canparse, keyin = Int32.TryParse(Console.ReadLine()) age <- keyin if canparse && age >= 0 && age < 151 then continueLooping <- false age

Code snippets - css

Lists, without indents, with buttons, and over-handing firstline
ul { list-style: disc outside none; margin-left: 0; padding-left: 1em; } ul.circle { list-style-type: circle; } /* for lists within lists */ li { padding-left: 0.5em; }
pre :- with CR wrapping a line
pre { white-space: pre-wrap; /* css-3 */ white-space: -moz-pre-wrap; /* Mozilla, since 1999 */ white-space: -pre-wrap; /* Opera 4-6 */ white-space: -o-pre-wrap; /* Opera 7 */ word-wrap: break-word; /* Internet Explorer 5.5+ */ }

Thursday, 25 June 2015

Snippet: Searching web pages.

The idea's from Professional F# 2.0, Chapter 17 (by Ted Neward, Aaron C. Erickson, Talbott Crowell, Richard Minerich). Because there are 4 of them I'll call them the fgang of four, or FoF. When searching a dropdown list via a form, a web page form may return a value or nothing at all. F# handles nothing at all with None. Suppose our database data contained:

type VacationLocation =
    { Name: string; Pop: int; Density: int; Nightlife: int }
let destinations =
    [ { Name = "New York"; Pop = 9000000; Density = 27000; Nightlife = 9 }
      { Name = "Munich"; Pop = 1300000; Density = 4300; Nightlife = 7 }
      { Name = "Tokyo"; Pop = 13000000; Density = 15000; Nightlife = 3 }
      { Name = "Rome"; Pop = 2700000; Density = 5500; Nightlife = 5 } ]

Our web page filters user selections by city name, population, population density, and night life. A user will often ignore a selection. So each selection will be an option. A first iteration of F# can handle it likewise, using the identity function id:

let getVacationPipeline nightlifeMin sizeMin densityMax searchName =
    match nightlifeMin with
    | Some(n) -> List.filter (fun x -> x.Nightlife >= n)
    | None -> id
    >> match sizeMin with
       | Some(s) -> List.filter (fun x -> x.Pop / x.Density >= s)
       | None -> id
    >> match densityMax with
       | Some(d) -> List.filter (fun x -> x.Density <= d)
       | None -> id
    >> match searchName with
       | Some(sn) -> List.filter (fun x -> x.Name.Contains(sn))
       | None -> id

This function is applied to the data like so:

let applyVacationPipeline data filterPipeline =
    data
    |> filterPipeline
    |> List.map (fun x -> x.Name)

with filterPipeline a general function to be applied for the where clause. The last line is the select clause.

let myPipeline = getVacationPipeline (Some 5) (Some 200) (Some 8000) None
applyVacationPipeline destinations myPipeline

This match ... with ... some ... None -> id is repetitive, so we abstract it out as a getFilter function. It becomes:

let getVacationPipeline2 nightlifeMin sizeMin densityMax searchName =
    let getFilter filter some =
        match some with
        | Some(v) -> List.filter (filter v)
        | None -> id
    getFilter (fun nlMax x -> x.Nightlife >= nlMax) nightlifeMin
    >> getFilter (fun sMax x -> x.Pop / x.Density >= sMax) sizeMin
    >> getFilter (fun dMin x -> x.Density < dMin) densityMax
    >> getFilter (fun sName x -> x.Name.Contains(sName)) searchName

We can invoke it like so:

let myPipeline2 = getVacationPipeline2 (Some 5) (Some 200) (Some 8000) None
applyVacationPipeline destinations myPipeline2

The FoF is more detailed, beginning with an imperative version (??). I suspect every C# programmer gave up such imperative code long ago for Linq.

F# automatically handles missing data. Because we can compose our queries, each may be simply tested too.

Monday, 5 January 2015

Russian propaganda (cyber-warfare?) example on twitter

Russia has been accused of funding and propagandising anti-fracking campaigns in the West1, 2. If the West can do it to Russia3, expect Russia to fight back. Natural gas is a famous Russian export but many energy exports (gas, oil, coal, nuclear power) are important to the Russian economy. The recent fall in the price of oil even precipitated an economic crisis there. Preventing fracking in Europe is a good way to keep natural gas prices high. They've already had a lot of success in that area.

Given they have the 'resources' in place, it seems obvious to turn against nuclear power too. One such example is their recent twitter campaign, using the hashtags #FukushimaAgain #Chernobyl2015. It's already been noted that the 'accident' to the reactor in the Ukraine was an incident not an accident4. Russian media sources are systematically misreporting the events in Ukraine, and at Ukraine nuclear reactors too5. As I write, I note that ans nuclear cafe is down. Can that be due to Russian cyber-warfare too? Unlikely, it's back up and it was giving a 502 server error. Nevertheless, who'd put anything past these people?

These are just the first 10 accounts I looked at tweeting those hashtags. I've no idea how many more there are of them.

These accounts don't, at first, look fake. A detailed investigation shows otherwise: they are hijacked or fake:

  • most of the accounts only began tweeting within the last few weeks
  • the accounts have a few hundred tweets each, often made very recently
  • they rarely, if ever, tweet to anyone else
  • they don't engage anyone in a conversation
  • many of the innocent looking tweets are garbage:
    • common quotes from famous people e.g.:
    • 'witty', or 'pseudo-intellectual' observations. e.g.:
  • here's an example of a tweet that belongs to a conversation. A message to a friend. Who might that be?:
  • tweets are often made with very short time intervals between them - indicating the person has nothing better to do than, essentially, repeat the same tweet. More like it's a bot using random time intervals.
  • tweets are likely to be gender neutral, geographically neutral. The bot doesn't know whether it's pretending to be male/female or whatever. The more specific the tweet, the more trouble a programmer must endure to fake it.

For more on fake twitter accounts see: 6

References

  1. NATO Chief: Putin Behind Anti-Fracking Campaigns
  2. Russia’s Quiet War Against European Fracking
  3. Russia says 'spies' work in foreign NGOs
  4. Reporting an Incident as an Accident
  5. Ukraine Nuclear Plants - Resources and Information
  6. 11 Easy Ways To Spot a Fake Twitter Account