All,
Does anyone have (or know of) an algorithm to find repeating
patterns of characters in a string ?
This started out as a mental exercise for moi, and the mouseUp logic
is untested:
on mouseUp
put field 1 into sourceString
put empty into patternList
put 6 into minPatternLength -- or whatever
put length(sourceString) div 2 into maxPatternLength -- pattern
can't be longer than half the length
if maxPatternLength < minPatternLength then exit mouseUp
repeat with patternLength = maxPatternLength down to minPatternLength
put ((length(sourceString) mod patternLength)-1)*patternLength
into maxStartPosition
-- pattern can't start within patterenLength-1 chars from end
put patternLength - 1 into endAdjustment
repeat with startingPoint = 1 to maxStartPosition
set cursor to busy
put startingPoint+endAdjustment into patternEnd
put char startingPoint to patternEnd of sourceString into targetPattern
if targetPattern is among the words of patternList then next
repeat -- may need stronger checking?
get the number of lines of offsets(targetPattern,char
(patternEnd+1) to -1 of sourceString)
if it > 0 then put targetPattern&&it&return after patternList
end repeat
end repeat
put patternList
end mouseUp
OTOH, working on it led me to the following offsets function, which
has been tested.
function offsets targetString, sourceString
put empty into offsetsList
put 0 into offsetAdjustment
put length(targetString)-1 into targetLengthAdjustment
repeat
get offset(targetString,sourceString)
if it = 0 then return offsetsList
put (it+offsetAdjustment) &return after offsetsList
put it+targetLengthAdjustment into deleteCutoff
delete char 1 to deleteCutoff of sourceString
add deleteCutoff to offsetAdjustment
end repeat
end offsets
Example: offsets("at","The cat in the hat smelled a rat where he sat.") returns
6
17
31
44
Note that the same logic can be applied to create lineOffsets,
itemOffsets, and wordOffsets functions.
Enjoy!
--
Rob Cozens
CCW, Serendipity Software Company
"And I, which was two fooles, do so grow three;
Who are a little wise, the best fooles bee."
from "The Triple Foole" by John Donne (1572-1631)
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