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Hi,
I found this code on internet, but I doesn't find anything, it returns 0 to me:

########CODE to copy and paste#######
function logarithmicSearch @pArray pItem pLeft pRight
local tIndex
local tResult
# create a new range pointer that points to the item that lies
# right between the left and right range pointers
put round ((pLeft + pRight) / 2) into tIndex
# if we have found the matching item then stop processing and return it
if pArray[tIndex] = pItem then
put tIndex into tResult
# if any of the range pointers have the same value
# then the item we are looking for does not exist in the array and we return 0
else if (pLeft = pRight or pLeft = tIndex or pRight = tIndex) then
put 0 into tResult
# if we have not yet found a match and none of the range pointers have the same
# value then call logarithmicSearch again with a smaller search range
# we are effectively halving the search area, each time we call logarithmicSearch
else if pArray[tIndex] > pItem then
put logarithmicSearch (pArray, pItem, pLeft, tIndex) into tResult
else
put logarithmicSearch (pArray, pItem, tIndex, pRight) into tResult
end if
return tResult
end logarithmicSearch
#####END OF CODE generated by http://tinyurl.com/j8xf3xq with livecode 9.0.0-dp-1#####

What's wrong?

No commas between params - does it even compile?

@Max

What Richard means is you have no data in which to fill your parameters. The function even calls for an array as one of them.

@Richard.

It does compile without commas. I did not think that was possible.

Craig

Hi Max,

the function is correct,
also with spaces instead of commas between params what is a legal definition**.

You found a LC lesson:
http://lessons.livecode.com/m/4071/l/11 ... h-an-array

What's wrong with that lesson is the call to the function.
An array tArray is filled with names. The example calls then
put logarithmicSearch (tSortedArray, "Best, Tony", 0, 15) -- wrong name of array.
This should read:
put logarithmicSearch (tArray, "Best, Tony", 0, 15) -- correct name of array.
With that correct call you get the correct result 3.

Hermann

________
** This is the function I used when testing this

[-hh] wrote:the function is correct,
also with spaces instead of commas between params what is a legal definition**.

Thanks. Never seen that before in any other LC examples, or any other language for that matter (including other xTalks).

The anomaly of having commas optional is made more curious by allowing that in the definition only. When calling a handler, any arguments not separated by commas throw an error.

FWIW. a tip about passing by reference:

That function passes the first arg by reference, denoted with a preceding "@". This can be useful when any modifications being made to the data should affect the original data, rather than work on a copy.

Historically "@" was also sometimes used for performance/memory reasons, to reduce an unnecessary copy of large data, as seems to be the case with this function. But since around v7.x and later, that's no longer needed. LC now uses "copy on write" for argument data. All read operations in arg data are done on the original data.

If the receiving handler modifies the data, at that point the data is copied. Unless of course you've told it to always use the original data with "@".

So the efficiency sought here in this read-only handler by using "@" is no longer needed. Newer versions of LC provide that efficiency by default.

Yes. I simply didn't want to change the function given in the search-an-array lesson.
These lessons were written in a very clear style several years ago and may be now updated in the sense of your post.

The problem is that logarthmic search looks for a sorted array. I thought that mine was sorted, but I was wrong.
This is the function to sort arrays: