I want to be able to add itemOrders to an ArrayList but then check to see if the itemOrder is already there. If that particular itemOrder is already in the ArrayList I only want one copy to remain. I can't figure out why this isn't deleting duplicate copies. I've even tried converting itemOrder to a string and checking to see if the strings are the same and deleting that way but I can't get it to work. Any help on what I'm doing wrong?
public void add(ItemOrder itemOrder) {
this.list.add(itemOrder);
for (int i=0; i< this.list.size(); i++){
if (this.list.get(i).equals(itemOrder)){
this.list.remove(i);
}
}
}
I get results like this.
Memory Format
[ItemOrder#4d459b26]
[ItemOrder#4d459b26, ItemOrder#343d0d2b]
[ItemOrder#4d459b26, ItemOrder#343d0d2b, ItemOrder#142b9cd8]
String Format
[silly putty, 3.95 (10 for 19.99), 1]
[silly putty, 3.95 (10 for 19.99), 1, silly string, 3.5 (10 for 14.5), 0]
[silly putty, 3.95 (10 for 19.99), 1, silly string, 3.5 (10 for 14.5), 0, silly putty, 3.95 (10 for 19.99), 1]
So what I think is happening is that its checking the memory of the itemOrder and since that's not the same it's letting a duplicate through. How can I fix this?
So what I think is happening is that its checking the memory of the itemOrder and since that's not the same it's letting a duplicate through. How can I fix this?
Yes, that is the default behaviour.
If you want the state / contents of the object to be compared, you have to implement equals (and if you do that, you also have to implement hashCode to match it).
In addition to that, as #alfasin points out, you cannot just remove elements from the list while iterating over it. That messes up indexes. Just check if the element is already in the list, and only add it if not.
Related
Example Sheet I'm trying to get an exact match with an array in the criteria section of dget. Maybe there is another way to work around this, but I'm trying to give it a dynamic component in the array.
=dget('Micro Data'!$A$1:J,"PCR Score",{"Micro Type","Stage Type","Tank","ID#";"PCR PAL","Bright",F2,H2})
Sometimes all criteria matches multiple data points except the "Tank". However the tanks won't exactly match. Ex. All the data is the same in two data sets, except the tanks are CT1 and CT18. This then comes up with the #NUM! error. I'm trying to find if there is a way to get an exact match in the array data while still allowing it to reference the cell?
I know there is the option of making it "=XXX" making it a txt string, but this would take away the dynamic function. I would also loose the auto updating aspect when more data is added.
Thanks
Ryan, see my solution using a query, in Retain Log-GK, cell F2. I think it is just as dynamic as the dget, but perhaps not. It will need some error wrapping to avoid errors if no result found.
Formula is basically:
=query('Criteria Source'!A2:J5,
"select J where B = '"&D9&"' and C = '"&D10&"' and E = '"&D11&"' and D ='"& D2 & "' ",0)
I made all of the criteria dynamic, though obviously you can do it whatever way suits you best...
Let me know of any questions. I'll check back later...
tNum={[2]=true , [3]=true,[4]=true, [5]=true ,[6]=true }
#tNum-->0
tNum={}
tNum[2]=true
tNum[3]=true
tNum[4]=true
tNum[5]=true
tNum[6]=true
#tNum-->6
why such a difference in size?
are both examples identical?
Your two tables are semantically identical, but using # on them is ambiguous. Both 0 and 6 are correct lengths. Here's an abridged version of the docs:
The length operator applied on a table returns a border in that table. A border in a table t is any natural number that satisfies the following condition:
(border == 0 or t[border] ~= nil) and t[border + 1] == nil
A table with exactly one border is called a sequence.
When t is not a sequence, #t can return any of its borders. (The exact one depends on details of the internal representation of the table, which in turn can depend on how the table was populated and the memory addresses of its non-numeric keys.)
This is an example of undefined behavior (UB). (That may not be the right word, because the behavior is partially defined. UB in Lua can't launch nuclear weapons, as it can in C.) Undefined behavior is important, because it gives the devs the freedom to choose the fastest possible algorithm without worrying about what happens when a user violates their assumptions.
To find a length, Lua makes, at most, log n guesses instead of looking at every element to find an unambiguous length. For large arrays, this speeds things up a lot.
The issue is that when you define a table as starting at index [2], the length operator breaks because it assumes that tables start at index [1].
The following code works as intended:
tNum = {[1]=false, [2]=true, [3]=true, [4]=true, [5]=true, [6]=true}
#tNum => 6
The odd behaviour is caused because when you initialize an array with tNum={} it initializes by assigning every index to nil, and the first index is [1] (It doesn't actually initialize every value to nil, but it's easier to explain that way).
Conversely, when you initialize an array with tNum={[2]=true} you are explicitly telling the array that tNum[1] does not exist and the array begins at index 2. The length calculation breaks when you do this.
For a more thorough explanation, see this section of the lua wiki near the bottom where it explains:
For those that really want their arrays starting at 0, it is not difficult to write the following:
days = {[0]="Sunday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Saturday"}
Now, the first value, "Sunday", is at index 0. That zero does not affect the other fields, but "Monday" naturally goes to index 1, because it is the first list value in the constructor; the other values follow it. Despite this facility, I do not recommend the use of arrays starting at 0 in Lua. Remember that most functions assume that arrays start at index 1, and therefore will not handle such arrays correctly.
The Length operator assumes your array will begin at index [1], and since it does not, it doesn't work correctly.
I hope this was helpful, good luck with your code!
I have an array of core data objects called samples, each sample has a depthFrom and depthToo. I load each sample into a tableView to show the depthFrom and Too. I need to check for gaps between the values and if there is, insert a new sample.
The samples in the table could look like below with depthFrom and depthToo,
The issue is since there is a gap between the numbers from 100 to 210 new samples should be added to the table. using a gap of 50 as much as possible so it would look like this with the auto generated samples.
What im unsure of is how to compare the values, i would rather do it as the view loads before cellForRowAtIndexPath is called so i would not need to reload the table again. I was thinking of looping through each value and comparing them but there all in the same array so im not sure how i would do this. I have all the data displaying correctly in my app its just the gaps i need to account for and if im able to find a way to compare the values in the array then i can manage adding in the new objects i just need pointing in the right direction as this is new to me.
If theres anything about my question that is confusing then just add a comment and i will update it accordingly, thanks for any help.
To fix the gaps, you must keep track of the last depthTo and check if there's a gap between it and the current sample. If there is, insert samples with a spacing of 50*, until we reach our current sample.
Here's a pseudocode solution:
samples = NSMutableArray
int lastDepthTo = 0;
for (i = 0; i < [samples count]; i++) {
s = samples[i]
// add missing samples (upto current s.depthFrom)
while (s.depthFrom > lastDepthTo) {
genDepthTo = MIN(d.depthFrom, lastDepthTo+50)
generated = new sample(depthFrom: lastDepthTo, depthTo: genDepthTo)
[samples insert:generated atIndex:i]
i++ // increment i to skip inserted sample
lastDepthTo = genDepthTo
}
lastDepthTo = s.depthTo
}
Note: this is untested, maybe off by 1 for the indexing of i.
I'm manipulating entries inside a DoubleLinkedQueue via the DoubleLinkedQueueElement.append/prepend methods. This results in the new elements being inserted into the queue, but fails to update the length, and the toList() method results in an error being thrown.
I understand queues are only supposed to have elements added at the start/end, but it looks like the interface should allow for adding in the middle via the entries. I find it hard to believe such a common/well understood data structure would have a bug at this point - so am I using DoubleLinkedQueues incorrectly? Is there another data structure that I should be using? I'm looking to merge values from another iterable into my own sorted iterable - a SplayTreeSet might get me there in n log n time, but a simple merge should get me there in linear time...
Example of code that acts unexpectedly:
main() {
var q = new DoubleLinkedQueue<int>.from([1]);
q.firstEntry().prepend(0);
print('length: ${q.length}');
int i = 0;
for (var qi in q){
print('${i++}: $qi');
}
}
Output:
length: 1
0: 0
1: 1
It looks like the length getter is only pointing to an internal counter. This is done because counting the elements everytime might take very long for long lists.
The internal counter is only updated if you use the methods that directly operate on the list instead of using the prepend method of an element. In your example you should use q.addFirst(0); which results in the length being updates. The .prepend() method just inserts a new element and changes the pointer. Which results in correct traversation of the elements, but the counter is wrong anyway.
Unfortunately it looks like you cannot insert elements in the middle of the list, nor can you make the list recount the elements. You should consider creating a bug over at www.dartbug.com.
// Update:
toList() throws an error because there are more elements than length.
I know of:
http://lua-users.org/wiki/SimpleLuaApiExample
It shows me how to build up a table (key, value) pair entry by entry.
Suppose instead, I want to build a gigantic table (say something a 1000 entry table, where both key & value are strings), is there a fast way to do this in lua (rather than 4 func calls per entry:
push
key
value
rawset
What you have written is the fast way to solve this problem. Lua tables are brilliantly engineered, and fast enough that there is no need for some kind of bogus "hint" to say "I expect this table to grow to contain 1000 elements."
For string keys, you can use lua_setfield.
Unfortunately, for associative tables (string keys, non-consecutive-integer keys), no, there is not.
For array-type tables (where the regular 1...N integer indexing is being used), there are some performance-optimized functions, lua_rawgeti and lua_rawseti: http://www.lua.org/pil/27.1.html
You can use createtable to create a table that already has the required number of slots. However, after that, there is no way to do it faster other than
for(int i = 0; i < 1000; i++) {
lua_push... // key
lua_push... // value
lua_rawset(L, tableindex);
}