counting runs

[Cubist at aol.com]

sez j.tangen at unsw.edu.au:
>I'm trying to solve a seemingly simple problem and I could use some  
>help. A coin flip will come out "Heads" or "Tails" and will produce,  
>for example, the following series for 20 flips:
>
>T,T,H,T,T,H,H,H,T,T,H,T,H,H,H,T,H,T,H,T
>
>I need to count up the number events for a particular run.  For example,
>
>Heads x 3 = 2
>Heads x 2 = 0
>Heads x 1 = 4
>Tails x 1 = 4
>Tails x 2 = 3
>Tails x 3 = 0
>
>I need to account for runs up to 60 (rather than 3 above) for  
>hundreds of flips (rather than 20 above).
   Presuming the data is indeed a string of Ts and Hs, separated by commas, 
something like this might do what you want...

local LongestRun = 60 # this value can be dialed up or down as desired

function FindRuns TheFlips
  # TheFlips must be a comma-delimited series of Ts and Hs!
  # if TheFlips is anything else, God knows what this handler will do to it

  put TheFlips into DerTempT
  put TheFlips into DetTempH

  put "T" into RunsT
  put "H" into RunsH
  repeat
    put RunsT into item (1 + the number of items in RunsT) of RunsT
    put RunsH into item (1 + the number of items in RunsH) of RunsH
    if (the number of items in RunsT => LongestRun) then exit repeat
  end repeat
  put ("," & (item 1 to LongestRun of RunsT) & ",") into RunsT
  put ("," & (item 1 to LongestRun of RunsH) & ",") into RunsH

  put true into TsLeft
  put true into HsLeft

  put "Record of Ts" into RezultT
  put "Record of Hs" into RezultH

  repeat with K1 = LongestRun down to 1 # or however many
    # first, let's see if we need to worry about any further runs
    put (offset ("T",DerTempT) > 0) into TsLeft
    put (offset ("H",DerTempH) > 0) into HsLeft

    if TsLeft then
      # we still have some Ts
      if offset (RunsT,DerTempT) > 0 then
        # hey, we got at least one run of this particular length!
        put the length of DerTempT into DerLength
        replace RunsT with "," in DerTempT
        # RunsT is a string of length (2n+1), where n is the number of Ts in 
it.
        # if we replace all instances of RunsT with single commas, that 
shortens
        # DerTempT by (2n) characters per instance that got replaced. 
therefore...
        put (DerLength - the length of DerTempT) div (2 * K1) into NumOfRuns
      else # nope, no more Ts left, hence no runs of however-many Ts
        put 0 into NumOfRuns
      end if
      put ("Heads x" & K1 && "=" && NumOfRuns) & return before RezultT
    end if

    # now do to the Hs what we did to the Ts
    if HsLeft then
      if offset (RunsH,DerTempH) > 0 then
        put the length of DerTempH into DerLength
        replace RunsH with "," in DerTempH
        put (DerLength - the length of DerTempH) div (2 * K1) into NumOfRuns
      else
        put 0 into NumOfRuns
      end if
      put ("Tails x" & K1 && "=" && NumOfRuns) & return before RezultH
    end if

    # now adjust RunsT and RunsH for the next time around the repeat loop
    delete char 1 to 2 of RunsT
    delete char 1 to 2 of RunsH
  end repeat

  # clean up RezultT and RezultH -- nuke the crap in the final line of each
  delete line -1 of RezultT
  delete line -1 of RezultH

  return RezultT & return & "=======" & return & RezultH
end FindRuns

   Hope this helps...