What if you set the C++ pointers to NULL immediately after deleting them in the destructors (not a MATLAB expert, so I'm not sure if you can do this with what you're doing)? The C++ standard says that deleting a NULL pointer is a no-op and always safe.
That's pretty weird. Still, all you would have to do is nullify the in-MATLAB C++ object reference in your MATLAB destructor, and only call the C++ destructor if the C++ reference hasn't been nullified. EDIT: Yup, Dragonmaster Lou and I had a similar thought.
Yeah, I did more debugging and it appears that the deconstructor isn't even being called twice. It's just crashing immediately after it deletes the first time. It's weird because when the deconstructor is called normally outside of the clear all command, it works just fine. I think it has to do with how MATLAB deletes classes and clears mex-files. But even then, I mexLocked the deconstructor mex files and was still encountering issues. I'm puzzled.
I looked this up a little, and there are a couple of things I've come up with. Here's how I understand it ought to work: Your C++ constructor returns an mxArray (i.e. the C implementation of MATLAB's sole data type) inside which you have a pointer to a C++ object. This mxArray is then being wrapped inside a handle class inside MATLAB which lets you group together all of the functionality associated with the C++ object.
Note that this mxArray wrapping is pretty important, and it needs to be allocated with mxMalloc and mexMakeMemoryPersistent, because it needs to behave just like any other MATLAB object and be able to be garbage-collected. Also, you've probably got to be careful with how you treat that pointer value, given MATLAB's data types.
In any case, when you do clear all there's several things being destroyed; for it to work it ought to happen in this order: (1) The handle object's destructor gets called, calling the MEX-destructor on your mxArray variable - both of these should still exist and retain their values and the mxArray should still hold the same pointer it held before. (2) The mxArray variable and the MEX-functions get destroyed (the order for these shouldn't matter).
This is for a class and I wouldn't be using visual basic if I didn't have to. I know for a fact this would work 1000 times better/simpler in python. X-posted from stackoverflow:
I'm using the following code to read in a highscores file with the score written first and the player's name written to the next line, and then display the top 3 scores or fewer if there aren't 3 scores written to the file. A highscores display should have the scores sorted with the highest first so that's what this program tries to implement. Array.sort() isn't doing a damn thing. In fact, the program's not even reversing the arrays like it should either. I've tested array.sort() this way with the names and scores arrays given explicitly and it works fine. I thought maybe it was still reading the data as string even though it's declared otherwise but it rounds off decimals when I change the array type to Integer so I'm pretty sure it's not that. I have no idea why reading the data in from a file changes how it's sorted. My teacher didn't understand what was going on either. Does anyone know what's going on here? Imports System.IO
Public Class Form2
Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Dim fileLines() = File.ReadAllLines(Application.StartupPath & "/../../Resources/highscores.txt") Dim highscores() As Double = {} Dim names() As String = {} 'For some reason vb doesn't have a function to add items to arrays. 'Lists have this capability, but if I used a list I couldn't use array.sort For i As Integer = 0 To fileLines.Length() - 1 If (i Mod 2 = 0) Then 'highscores.add(fileLines(i) Array.Resize(highscores, highscores.Length + 1) highscores(highscores.Length - 1) = fileLines(i) Else 'names.add(fileLines(i)) Array.Resize(names, names.Length + 1) names(names.Length - 1) = fileLines(i) End If Next Array.Sort(highscores, names) highscores.Reverse() names.Reverse() If highscores.Length() > 0 Then Label1.Text = Str(highscores(0)) + " " + names(0) End If If highscores.Length() > 1 Then Label2.Text = Str(highscores(1)) + " " + names(1) End If If highscores.Length() > 2 Then Label3.Text = Str(highscores(2)) + " " + names(2) End If End Sub End Class
Why aren't you reading the documentation? It will save you a lot of stress.
I was reading the array.sort documentation but it didn't help because my problem was due to an error in the file I was reading. I agree that the array.reverse documentation would have helped me, but that was a secondary issue to the array.sort issue.
I'm working on a program to make a robot follow a bezier curve. Basically, it generates parametric equations for x and y as polynomials in terms of t and takes the derivatives of each. It takes arctan(dy/dx) to find the angle it should currently be moving at, compares it to its current angle, and moves in an arc to adjust. It moves at a constant speed (average of left and right wheel speeds) and uses the arc length equation to find how much to increase t by based on the distance traveled.
Is there an easier way to adjust my angle than arctan? I'm afraid that as the robot crosses vertical, the high tan values will cause problems and inaccuracy. Finding the rate of change of angle directly would be great, if possible.
So I've been playing some chess on my phone and I was considering trying to make an Android chess game. While there are quite a few already I've noticed that there doesn't seem to be any with online multi. I was trying to think of easy ways to do this and I thought that one easy way might be to export to some format (PGN?) and send to the other player via SMS. I'm not really familiar with mobile development so I was wondering if someone more experienced could confirm my approach or suggest an alternative.
At the moment it's just embedded Javascript using the Google Maps API. If anyone wants to contribute or make suggestions, feel free. One thing I guess it needs is a way of showing the distances corresponding to the contours; does anyone have a good idea on how to do that?
Also, a couple of new features: - Click and drag PAXes to move them around. - Click on an empty part of the map to make a new PAX. - Right click on an existing PAX to destroy it.
We need a PAX Africa!
next astep, make it a contour based on travel time to any PAX.
Too hard Anyone have other suggestions?
I figure a distance-based legend would be in order, but I haven't done one yet.
Comments
EDIT: Yup, Dragonmaster Lou and I had a similar thought.
Your C++ constructor returns an mxArray (i.e. the C implementation of MATLAB's sole data type) inside which you have a pointer to a C++ object. This mxArray is then being wrapped inside a handle class inside MATLAB which lets you group together all of the functionality associated with the C++ object.
Note that this mxArray wrapping is pretty important, and it needs to be allocated with mxMalloc and mexMakeMemoryPersistent, because it needs to behave just like any other MATLAB object and be able to be garbage-collected. Also, you've probably got to be careful with how you treat that pointer value, given MATLAB's data types.
In any case, when you do
clear allthere's several things being destroyed; for it to work it ought to happen in this order:(1) The handle object's destructor gets called, calling the MEX-destructor on your mxArray variable - both of these should still exist and retain their values and the mxArray should still hold the same pointer it held before.
(2) The mxArray variable and the MEX-functions get destroyed (the order for these shouldn't matter).
Next AI project is autonomous soaring with thermal updrafts. Here is my day 1 air current simulator.
http://msdn.microsoft.com/en-us/library/b0zbh7b6.aspx
Edit: Just checked, it can't.
Is there an easier way to adjust my angle than arctan? I'm afraid that as the robot crosses vertical, the high tan values will cause problems and inaccuracy. Finding the rate of change of angle directly would be great, if possible.
Prettttttyyyyyyyyy
https://github.com/lackofcheese/PAX-contour-map
It's a work in progress (right now it only handles distance from a single location), but it already looks fairly cool so I thought I'd post it. If you want to view the HTML file directly, use this link:
http://htmlpreview.github.com/?https://github.com/lackofcheese/PAX-contour-map/blob/master/map.html
At the moment it's just embedded Javascript using the Google Maps API. If anyone wants to contribute or make suggestions, feel free. One thing I guess it needs is a way of showing the distances corresponding to the contours; does anyone have a good idea on how to do that?
This will make Africa even worse for getting to PAX.
http://htmlpreview.github.com/?https://github.com/lackofcheese/PAX-contour-map/blob/master/map.html
Also, a couple of new features:
- Click and drag PAXes to move them around.
- Click on an empty part of the map to make a new PAX.
- Right click on an existing PAX to destroy it.
We need a PAX Africa! Too hard
Anyone have other suggestions?
I figure a distance-based legend would be in order, but I haven't done one yet.