Relationships between strings

[marko001 2]

Hi all,

just a tricky request:

which are the relationships between strings?

I mean, when it can happen then

$vValue < $avArray[$iMid]
 
given, for example,
 
$value = <z:row c0='Sims2000' Platform='DS'
$avArray[$iMid] = <z:row c0='AlphaZero' Platform='Wii' Price='12.99'/>

?

This is simpy part of _arraybinarysearch() and I can't understand when a given string is lower or higher than another one

_arraybinarysearch() uses a binary method to search trough array and given the result ($vValue < $avArray[$iMid]) it gives a +/- 1 to $mid and cycle again

My tries always return the relationship with "<" but I can't understand which logic is used to set a value lower or higher than another one..

M.

[JohnOne 1,603]

I think it uses some sort of alphabetical comparison.

EDIT

lexicographical

Edited October 2, 2011 by JohnOne

[czardas 1,269]

I'm going to hazard a guess, since the code you posted doesn't use _ArrayBinarySearch. Binary representations of strings are numerical. Perhaps that's the answer?

Edited October 2, 2011 by czardas

[BrewManNH 1,305]

I'm going to hazard a guess, since the code you posted doesn't use _ArrayBinarySearch. Binary representations of strings are numerical. Perhaps that's the answer?

The Binary part of it's name isn't because it uses binary comparisons,it's because the type of search it does is called that. It takes your search pattern, and looks at the halfway point in the array for it, if it's higher it jumps 50% higher into the array to see if it's there, if it's lower it searches 50% lower in the array. By dividing the remaining portion of the array by 50% every iteration it finds the string faster than searching the whole string one item at a time. This is why the array has to be sorted for it to work correctly, because otherwise you will either not find the pattern or it will take a very long time.

[czardas 1,269]

BrewManNH

Thanks for the explanation. I never used _ArrayBinarySearch, but the name is clearly misleading. Coming from a different background I am often bemused by programming terms: Had the function been called _ArrayDeadReckoningSearch it would have made perfect sense to me. As it stands, it just seems to be a misnomer. Perhaps I've been out of school too long.

Edited October 3, 2011 by czardas

[BrewManNH 1,305]

I didn't understand what it meant when I first ran across it myself, the name didn't go with what it did in my mind until I looked it up. I think that this article might explain it a bit better. It's a little confusing but you get the highlights of how it's supposed to work and why it's named what it is. Other than the fact that it needs a sorted array to work correctly, and the current version of it only works on 1D arrays, I'm surprised it isn't used more for large array searching.

BTW, I have created a 2D version of it that searches a sub-item ("column") of the 2D array, the _Array.au3 link in my signature links to a modified Array.au3 file that includes several modified 2D capable array functions.

[czardas 1,269]

Thanks I'll take a look. Actually Dead Reckoning is not the term I'm looking for although its similar. The term I am looking for is what drafsten have always done with a compass Well anyway, its always good to learn new stuff.

I get the binary part now, although

Edited October 3, 2011 by czardas