Drawing the call stack in a recursive method - algorithm

I want to draw the call stack for any recursive method, so I've created a schema like this,
recursiveMethod(){
//Break recursion condition
if(){
// Add value here to the return values' list- No drawing
return
}
else{
//Draw stack with the value which will be pushed to the stack here
variable <- recursiveMethod()
//Clear the drawing which represents the poped value from the stack here
return variable
}}
Applying the schema will look something like this,
Notes:
This schema can draw recursive methods with n recursive call by making the recursive calls in a separate return statements.
returnValues list, is a list which save all the return values, just for viewing issues.
Draw stack means, simply Draw a simple cell "rectangle" + Drawing the pushed String.
What do you think of this? any suggestions are extremely welcomed.

I'm not sure if I understand your question correctly, but will take a stab at it, let me know if this is incorrect.
What I gather is that you want some way to keep track of you stack within a recursive function. One way you can do this is to have a Stack data structure, and a function that draws the data structure,how you wish to draw it is up to you, for now maybe just draw the stack as something like [---] with the '-' being the recursive depth.
Here is an approximate C++ like example:
So we have:
Stack recursiveFunctionTrackingStack; //Stack of something, maybe just '-'
void DrawStack(const Stack& aStack);
and another type something like:
struct StackUpdater
{
StackUpdater(){ recursiveFunctionTrackingStack.push('-'); }
StackUpdater(const string& somevalue)
{
recursiveFunctionTrackingStack.push(somevalue);
}
~StackUpdater(){ recursiveFunctionTrackingStack.pop(); }
}
so the 'StackUpdater' pushes something on the Stack data structure when an object of it is created, and pops it off when it is destructed.
Now within the recursive function we can do (using your code snippet):
recursiveMethod(){
if(){ return }
else{
{
StackUpdater su(pushedInValue); //Value pushed
variable <- recursiveMethod();
DrawStack(recursiveFunctionTrackingStack);
} //Value popped on destruct.
DrawStack(recursiveFunctionTrackingStack);
return variable
}}
Maybe what you want is something along those line. If not, then please clarify you question.
Hope this helps anyway.

Related

Processing - If statement and ids

I'm an Italian student and I'm new in programming. I need your help for a school project.
I'm making a blob tracking program using Daniel Shiffman's tutorials. Currently I have 2 blobs on the screen. I am identifying them with 2 IDs: number 0 and number 1.
I need to put some conditions on those blobs: if one blob is in a certain part of the screen and the other one is in another part, I need to call a function.
I don't know how to put the if conditions separately for the two ids. Below is some pseudo code of what I would like to achieve:
for (id==0)
if (...) and
for (id==1)
if(...) then {
void()
}
I would really appreciate any help!
I don't really know where you want the blobs to be when the desired function fires, but I can try to give you an example...
Blob
Assign some sort of position variable, in this case PVector, to your blob object.
class Blob {
PVector position;
Blob (PVector position) {
this.position = position;
}
void update() {
*random movements, etc...*
}
}
Create two blob objects
Create two objects and assign a position to each of them.
Blob[] blobs = new Blob[2];
void setup() {
size(400, 400);
blobs[0] = new Blob(5, new PVector(40, 40));
blobs[1] = new Blob(13, new PVector(100, 100));
}
Check if blobs is at left or right side of the screen
I check if blob[0] is at the left side of the screen and if blob[1] is at right side of the screen. If they are, at the same time, the desiredFunction(); will fire.
void draw() {
for (int i = 0; i < blobs.length; i++) {
blobs.update();
}
if (blobs[0].position.x < (width / 2) && blobs[1].position.x < (width / 2) {
desiredFunction();
}
}
Remember
This is just an example. You could of course check other parts of the screen instead of the left and right parts. You can also use IDs on your blobs instead of an array, I just thought it was better to just use an array in this case.
PS: I wrote this answer without having processing started. The code has certainly a couple of typing errors.
For the example you have described, you can achieve this using the && operator in one if statement.
First assign the conditions you want to test to boolean variables. For example, create the boolean variables id0IsThere, and id1IsThere, and set them to true if the blobs are in the locations you want them to be in. Then use the following if statement:
if (id0IsThere && id1IsThere) {
yourFunction();
}
The && operator means that the code inside the if statement that executes yourFunction() is only executed if both conditions are true. In this case, if both blobs are in the positions you want them to be in. Hope that helps. Read more about if statements and the && operator here:
https://processing.org/reference/if.html
https://processing.org/reference/logicalAND.html

Swift assign function to var cause retain cycle?

I met a similar question in Swift Memory Management: Storing func in var but that didn't solve my problem.
Here is my class definition:
class Test {
var block: (() -> Int)?
func returnInt() -> Int {
return 1
}
deinit {
print("Test deinit")
}
}
I tried two ways to assign value to block property and got completely different result. The second approach didn't cause retain circle, which is quite unexpected:
var t = Test()
// This will lead to retain cycle
// t.block = t.returnInt
// I thought this will also lead to retain cycle but actually didn't
t.block = {
return t.returnInt()
}
t = Test()
In my opinion, variable t is captured by block while block is a property of t, so can anyone explain why there isn't a retain cycle?
In Swift, all captured variables are captured by reference (in Apple Blocks terminology, all captured local variables are __block). So the t inside the block is shared with the t outside the block; the block does not hold an independent copy of t.
Originally, there is a retain cycle in the second case too, as the block holds a reference to this shared copy of t, and t points to the first Test object, and that Test object's block property points to the block. However, when you re-assign the shared variable t (which is visible both inside and outside the block), you break the retain cycle, because t no longer points to the first Test object.
In the first case, the t is effectively captured by value, because the t is evaluated immediately in the expression t.returnInt rather than be captured as a variable in a block. So a reassignment of t outside the block later has no effect on the block, and does not break the retain cycle. So you can think of
t.block = t.returnInt
as kind of like
let tmp = t
t.block = {
return tmp.returnInt()
}

AS2, Referencing a Changing Object Name

so I was wondering if there was a way to reference different objects on stage with he same method to save repeating lots of lines of code. This is what I have right now
function bossKilled(i:Number):Void {
trace("Boss Killed!");
kills ++;
_root.bossDeath.gotoAndPlay(2);
_root["pirate"+i+"Active"] = false; //name of variable would be pirate1Active
_root["pirate"+(i+1)+"Active"] = true; //name of variable would be pirate2Active
bossDeath._x = _root["pirate"+i+"Active"]._x;
bossDeath._y = _root["pirate"+i+"Active"]._y; }
However, this reference does not actually affect the variables. I was wondering if this was possible, and if so, what am I doing wrong?
Thanks.
Not sure what you try to achieve ... pirate1Active is a BOOL. A BOOL has no _x or _y property (nor any other).
If you are not sure where to find your objects in the object tree, you can use the debugger or add some traces on the MCs timeline, like trace (_parent);
Consider switching to AS3, it is much more object oriented and has better tools support.

Check of checkmate in chess

I am using this object oriented design of chess. I have implemented generating of valid moves for all pieces. Now I am trying implement check of checkmate.
I tried to make a method, which if player have moves, which cancel the checkmate. But the program end with StackOverflowError.
I delete the method. But the pseudoalgorithm of the method was something like that
boolean isGameOver(arg){
if(playerIsInCheck){
if(!hasValidMoves){
print("checkmate");
return true;
}
else{
return false;
}
}
else{
if(!hasValidMoves){
print("stalemate");
return true;
}
else{
return false;
}
}
}
I don't know how to check if the move cancel the checkmate. Can anyone advise me? I do not need all the code written in any programming language. Pseudoalgorithm will be sufficient.
The algorithm for checking for checkmate is as follows:
public boolean checkmated(Player player) {
if (!player.getKing().inCheck() || player.isStalemated()) {
return false; //not checkmate if we are not
//in check at all or we are stalemated.
}
//therefore if we get here on out, we are currently in check...
Pieces myPieces = player.getPieces();
for (Piece each : myPieces) {
each.doMove(); //modify the state of the board
if (!player.getKing().inCheck()) { //now we can check the modified board
each.undoMove(); //undo, we dont want to change the board
return false;
//not checkmate, we can make a move,
//that results in our escape from checkmate.
}
each.undoMove();
}
return true;
//all pieces have been examined and none can make a move and we have
//confimred earlier that we have been previously checked by the opponent
//and that we are not in stalemate.
}
I can't tell you why you are getting a stack overflow without seeing your method definitions, but I can explain how you check for mate-cancelling moves ( no pseudocode, sorry).
Basically, you generate a List of all possible Moves (Pseudolegals) and you let your programm try each of them. If the players king is no longer hittable in the resulting position (in your case you use the IsInCheck method), the current move is cancelling the mate.
If you do need the pseudocode, write a comment and I'll see what I can do.

what differs 2 function calls in a row?

Suppose you look at the stack and registers of a process which has the following code...
...
void Test()
{
for (int i = 0; i < 10; i++)
{
OneRunDontKnow();
}
}
...
You look at the stack twice exactly when the process executes the loop, and in both times the OneRunDontKnow is at the top of the stack.
Can you somehow know if OneRunDontKnow was popped out of the stack and then pushed in again or if it was never popped out?
EDIT: OneRunDontKnow can have any signature (it can also take parameters or return a value).
Probably the best way is to look at your assembled code. OneRunDontKnow() takes no parameters, so the only thing on the stack will be the instruction pointer, and other stack frame stuff, but no parameters. So find the place in the disassembly where OneRunDontKnow() should be called, and see what kind of PUSH and JMP inside the code where LOOP_ (LOOP, LOOPE, etc) is.

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