I'm really unsure about handling tables in the C API of Lua.
The interface I'm currently developing requires me to read
contents of a table given to my c function:
example.lua:
myVector2 = {["x"]=20, ["y"]=30}
setSomePosition(myVector2)
C function I register as "setSomePosition":
static int lSetSomePosition(lua_State *L)
{
//number of arguments
if(lua_gettop(L) != 1)
{
//error handling
return 0;
}
//Need your help with the following:
//extract tables values of indexes "x" and "y"
return 0;
}
I know there are a couple of ways handling tables of which you sometimes need to know the indexes which I do. I'm just confused right now about this and the more I research the more I get confused. Probably because I don't really know how to describe what I'm after in proper terminology.
Would really appreciate some good commented example code of how you would fill in the gap in my c function :)
(If you've got an easy to understand guide to this topic don't mind commenting)
lua_getfield(L, 1, "x") //pushes a value of t["x"] onto the stack
lua_tonumber(L, -1) //returns the value at the top of the stack
lua_getfield(L, 1, "y") //pushes a value of t["y"] onto the stack
lua_tonumber(L, -1) //returns the value at the top of the stack
Related
For class I have to make a program that calculates the birthday problem
Now I'm having trying to learn kotlin at the same time and I'm having trouble with a little snippet of code:
val checkSet = mutableSetOf<Int>()
generateSequence{ Random.nextInt(n)}.forEach {
if(!checkSet.add(it)) {
return#outForeach
}
}
outForeach#
sum += checkSet.size
As you can see I'm trying to do this with an infinite sequence. Kotlin doesn't accept this as outForeach is an unresolved reference. But this doesn't work either:
val checkSet = mutableSetOf<Int>()
generateSequence{ Random.nextInt(n)}.forEach {
if(!checkSet.add(it)) {
return#forEach
}
}
sum += checkSet.size
This will just start the forEach loop again. Is there a way to implement something as a forEachUntil or so?
p.s. I'm aware that this looks a lot like this question: 'return' doesn't jump out of forEach in Kotlin It's just that I don't really get the answers and I don't know if its applicable here. Also a way to implement forEachUntil seems for me to be far more elegant
Alternatives you may want to consider instead of first:
using a simple while without body:
while (checkSet.add(Random.nextInt(n))); // <- that semicolon is required! otherwise you execute what is coming next within the while
using run with a label:
run outForeach#{
generateSequence{ Random.nextInt(n)}.forEach {
if(!checkSet.add(it)) {
return#outForeach
}
}
}
maybe also takeWhile might be helpful. In this specific case however it is surely not (as it would check against the checkSet and leave us with a sequence that isn't consumed... but if the condition would be different, it may make sense to consider something like take, takeWhile, takeLast, etc.):
generateSequence { Random.nextInt(n) }
.takeWhile(checkSet::add) // as said: for this specific condition it doesn't make sense...
.forEach { /* do nothing except consume the sequence */ } // the same values you added to the set would be available in this step of course
I think I found the solution myself:
val checkSet = mutableSetOf<Int>()
generateSequence{ Random.nextInt(n)}.first { !checkSet.add(it) }
sum += checkSet.size
Basically use the function first() and keep returning false until you want to get out of the loop. And just drop the return of the function first()
I am using switch case into my method like in screenshot
I already done with Enumeration but how can I directly pass int constant into case??
I googled it but I found it with Enumeration
Please help me with it
If that's all the functionality you want to achieve then you should write something like this:
if (index.row == value) {
// logic when it's that row
} else {
// default case
}
What you tried to do is simply not possible, see the two questions linked by Martin R in the comments.
i am developing an ea that requires me to compare the high of previous 2 bars and whichever one is higher, use that as a stop loss value.
same for opposite side trades, i need to compare previous 2 lows and use the lower one as stop loss value.
what i am doing is this:-
void onTick()
{
static int ticket=0;
double ab=(//calculation for ab);
double de=(//calculation for de);
if(Low[1]<Low[2])
double sll=Low[1];
if(Low[1]>Low[2])
double sll=Low[2];
if(buy logic comes here)
{
double entryPrice=////////;
double stoploss=sll-xyz;
double takeprofit=entryPrice+((entryPrice-stoploss)*3);
ticket = OrderSend(Symbol(),...entryPrice,stoploss,takeprofit,.....);
}
if(ticket == false)
{
Alert("Order Sending Failed");
}
}
the problem is i am not able to reference the values of sll and get an error message saying "sll undeclared identifier"
i am fairly new to programming and would appreciate if someone can help me out with this.
I have added most of the code for you to understand the logic.
you would have to declare them outside the scope of the if statements if you want to use variables anywhere else so instead of doing that take a look at this
double sll; // declare sll outside the if statements
if(Low[1]<Low[2])
sll=Low[1];
if(Low[1]>Low[2])
sll=Low[2];
if(buy logic comes here)
{
bool res = OrderSend(..........);
}
Judging by what you wrote, it looks like you may be using res somewhere else too which then you need to define outside of the if statement because scoping.
I am creating a game in which, depending on the number of 'swipes' chosen to do, (let's say 3), 3 different patterns show on the screen, one by one. I am working on developing the first pattern.
So I have this:
if (swipes.no_of_swipes) == 3 {
swipeArray = Array<UInt32>(count: 3, repeatedValue: 0)
for i in 0 ..< 3 {
swipeArray[i] = arc4random_uniform(84)}
}
As far as I am aware, this code creates an array with three UInts which can be accessed by doing swipeArray[0], swipeArray[1], and swipeArray[2]. My first question is how long will this swipeArray stay the same? Until the close the view? Should I have a 'refresh button' when the user loses - and if so, how would I make one?
Then I have a property observer. You will notice the for loop, which I am using to keep code concise. I understand that I could do something like x++ somewhere in here so that it will go through each one.
var playBegin: Bool = false{
didSet {
if playBegin == true {
println("\(playBegin)")
var swipes = Menu()
if (swipes.no_of_swipes) == 3 {
for i in 0 ..< 3 {
patternRoom.image = UIImage(named: "pattern\(swipeArray[x])")
//rest of code
}
}
}
The pattern image comes from a set of 84 images named like pattern7 and pattern56. My second question is, how could I code the for loop to go through each swipeArray[x].
Thank you in advance,
Will
how long will this swipeArray stay the same?
This is a bit too open ended. It’ll stay the same until you assign a new value to it, either from this same bit of code or a different part. Only you can know when that will be, by looking at your code.
Since you express an interest in keeping the code concise, here’s a couple of code tips.
You might think about writing your first snippet’s loop like this:
swipeArray = (0..<swipes.no_of_swipes).map { _ in
arc4random_uniform(84)
}
This combines creating a new array and populating the values. By the way, just in case you don’t realize, there’s no guarantee this array won’t contain the same value twice.
It’s also probably better to make swipeArray of type [Int] rather than [UInt32], and to convert the result of arc4random to an Int straight away:
Int(arc4random_uniform(84))
Otherwise the UInt32s will probably be a pain to work with.
For your second for loop, you can do this:
for i in swipeArray {
patternRoom.image = UIImage(named: "pattern\(i)")
// rest of code
}
When writing Swift, usually (but not always), when you find yourself using array[x] there’s a better more expressive way of doing it.
After upgrading to MT 4.0, my TableViews that previously were displaying indexes on the right hand border are no longer working. The tableview still displays in sections and works properly, but the index is not displaying.
I have these three methods defined in my UITableViewSource, and all three appear to be working:
public override string[] SectionIndexTitles(UITableView tableView)
public override int SectionFor(UITableView tableView, string Title, int atIndex)
public override string TitleForHeader(UITableView tableView, int section)
Is anyone else having this problem? Is this a bug with MT 4.0?
This is a known bug.
It appears that UITableView is not retaining the returned array, you can use
the following to work around this issue while we investigate it further:
NSArray array;
[Export ("sectionIndexTitlesForTableView:")]
public NSArray SectionTitles (UITableView tableview)
{
if (array == null) {
string[] titles = new string[RowsInSection(tableview, 0)];
for (int index = 0; index < titles.Length; index++)
titles[index] = index.ToString();
array = NSArray.FromStrings (titles);
}
return array;
}
This was showing to me just numbers (index for each item of the section 0 (like A letter of the index), so I found that must change this to:
NSArray array;
[Export ("sectionIndexTitlesForTableView:")]
public NSArray SectionTitles (UITableView tableview)
{
if (array == null)
{
array = NSArray.FromStrings (SectionIndexTitles(tableview));
}
return array;
}
To all people who don't get the workaround to work correctly:
For me it was because I left the MonoTouch override method SectionIndexTitles in there - as soon as I removed it (or in my case renamed it so it can be called from the workaround), it worked as described :)
Getting the same problem, but the above fix did not work, I am sure it is probably something simple that I am doing wrong. The below methods are part of a UITableViewSource. All working as it was before MT 4.0, however the textual Index is not appearing. Debug output listed below the code shows that SectionTitles is not being called. Any thoughts on how this differs from the solution above, and how to get it working? Happy to start a new thread on this, but thought that it might be useful to have more information on this question instead.
NSArray array;
[Export ("sectionIndexTitlesForTableView:")]
public NSArray SectionTitles(UITableView tableview)
{
Debug.WriteLine("SectionTitles");
if (array == null)
{
array = NSArray.FromStrings(SectionIndexTitles(tableview));
}
return array;
}
public override string[] SectionIndexTitles(UITableView tableView)
{
Debug.WriteLine("SectionIndexTitles");
var sectionIndexTitles = Root.Sections.Select(section => section.IndexTitle ?? string.Empty);
var applySectionIndexTitles = sectionIndexTitles.Any (sectionIndexTitle => !string.IsNullOrEmpty (sectionIndexTitle));
foreach (string s in sectionIndexTitles)
{
Debug.WriteLine(s);
}
Debug.WriteLine("applySectionIndexTitles = " + applySectionIndexTitles);
return applySectionIndexTitles ? sectionIndexTitles.ToArray () : null;
}
Debug output:
SectionIndexTitles
A
B
C
D
E
F
G
H
J
K
L
M
N
O
P
R
S
T
W
applySectionIndexTitles = True
Wow, the answers here are a extremely misleading. Where do I start?
First, why are the examples using a backing NSArray? Why not a string [] for the backing data? Just because the method returns a NSArray doesn't mean you have to back it with an NSArray. Yikes. Why would you use an NSArray unless you have to. You don't have to here.
Second, realistically, I always store my index titles in a backing string []. That is normal use I'd say. Why wouldn't you do that anyway? The answers here make it sounds like it's a special case or something where you have to store it. As far as I know you are always responsible for doing that anyway. And another example relying on the cells to get data... Why on earth? If you can't simply use an array then get a clue that your array is out of scope or something.
Also, some people mentioned to not override as you normally would. Ummm... I don't know about that. That completely contradicts all the monotouch code I've seen. I've seen a lot of examples do both and it makes sense. Look at some of the template UIViewController constructors. The internal calls that explicitly reference selectors will need the selector. Normally you wouldn't need one but in this case apparently something internal is broken referencing the selector. That is NOT a reason to ditch overriding it as you normally would. You still need to override it in case you have some external call that came from your own managed code. You should absolutely still override it. Unless you always explicitly referencing selectors in YOUR code... then keep it overriden.
Anyway, a lot of this is my general monotouch understanding and I could be wrong. I mean, I don't know... I'm seriously not trying to criticize. I just had to comment because it looks like to me there is A LOT of bad information in this thread and I'm hoping this post will help someone who might be getting misinformed.