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  • [Ruby] Modifying object inside a loop doesn't change object outside of the loop?

    - by Jergason
    I am having problems with modifying objects inside blocks and not getting the expected values outside the blocks. This chunk of code is supposed to transform a bunch of points in 3d space, calculate a score (the rmsd or root mean squared deviation), and store both the score and the set of points that produced that score if it is lower than the current lowest score. At the end, I want to print out the best bunch of points. first = get_transformed_points(ARGV[0]) second = get_transformed_points(ARGV[1]) best_rmsd = first.rmsd(second) best_points = second #transform the points around x, y, and z and get the rmsd. If the new points # have a smaller rmsd, store them. ROTATION = 30 #rotate by ROTATION degrees num_rotations = 360/ROTATION radians = ROTATION * (Math::PI/180) num_rotations.times do |i| second = second * x_rotate num_rotations.times do |j| second = second * y_rotate num_rotations.times do |k| second = second * z_rotate rmsd = first.rmsd(second) if rmsd < best_rmsd then best_points = second best_rmsd = rmsd end end end end File.open("#{ARGV[1]}.out", "w") {|f| f.write(best_points.to_s)} I can print out the points that are getting stored inside the block, and they are getting transformed and stored correctly. However, when I write out the points to a file at the end, they are the same as the initial set of points. Somehow the best_points = second chunk doesn't seem to be doing anything outside of the block. It seems like there are some scoping rules that I don't understand here. I had thought that since I declared and defined best_points above, outside of the blocks, that it would be updated inside the blocks. However, it seems that when the blocks end, it somehow reverts back to the original value. Any ideas how to fix this? Is this a problem with blocks specifically?

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  • Const references when dereferencing iterator on set, starting from Visual Studio 2010

    - by Patrick
    Starting from Visual Studio 2010, iterating over a set seems to return an iterator that dereferences the data as 'const data' instead of non-const. The following code is an example of something that does compile on Visual Studio 2005, but not on 2010 (this is an artificial example, but clearly illustrates the problem we found on our own code). In this example, I have a class that stores a position together with a temperature. I define comparison operators (not all them, just enough to illustrate the problem) that only use the position, not the temperature. The point is that for me two instances are identical if the position is identical; I don't care about the temperature. #include <set> class DataPoint { public: DataPoint (int x, int y) : m_x(x), m_y(y), m_temperature(0) {} void setTemperature(double t) {m_temperature = t;} bool operator<(const DataPoint& rhs) const { if (m_x==rhs.m_x) return m_y<rhs.m_y; else return m_x<rhs.m_x; } bool operator==(const DataPoint& rhs) const { if (m_x!=rhs.m_x) return false; if (m_y!=rhs.m_y) return false; return true; } private: int m_x; int m_y; double m_temperature; }; typedef std::set<DataPoint> DataPointCollection; void main(void) { DataPointCollection points; points.insert (DataPoint(1,1)); points.insert (DataPoint(1,1)); points.insert (DataPoint(1,2)); points.insert (DataPoint(1,3)); points.insert (DataPoint(1,1)); for (DataPointCollection::iterator it=points.begin();it!=points.end();++it) { DataPoint &point = *it; point.setTemperature(10); } } In the main routine I have a set to which I add some points. To check the correctness of the comparison operator, I add data points with the same position multiple times. When writing the contents of the set, I can clearly see there are only 3 points in the set. The for-loop loops over the set, and sets the temperature. Logically this is allowed, since the temperature is not used in the comparison operators. This code compiles correctly in Visual Studio 2005, but gives compilation errors in Visual Studio 2010 on the following line (in the for-loop): DataPoint &point = *it; The error given is that it can't assign a "const DataPoint" to a [non-const] "DataPoint &". It seems that you have no decent (= non-dirty) way of writing this code in VS2010 if you have a comparison operator that only compares parts of the data members. Possible solutions are: Adding a const-cast to the line where it gives an error Making temperature mutable and making setTemperature a const method But to me both solutions seem rather 'dirty'. It looks like the C++ standards committee overlooked this situation. Or not? What are clean solutions to solve this problem? Did some of you encounter this same problem and how did you solve it? Patrick

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  • How to convert this query to a "django model query" ?

    - by fabriciols
    Hello ! What i want is simple : models : class userLastTrophy(models.Model): user = models.ForeignKey(userInfo) platinum = models.IntegerField() gold = models.IntegerField() silver = models.IntegerField() bronze = models.IntegerField() level = models.IntegerField() rank = models.IntegerField() perc_level = models.IntegerField() date_update = models.DateTimeField(default=datetime.now, blank=True) total = models.IntegerField() points = models.IntegerField() class userTrophy(models.Model): user = models.ForeignKey(userInfo) platinum = models.IntegerField() gold = models.IntegerField() silver = models.IntegerField() bronze = models.IntegerField() total = models.IntegerField() level = models.IntegerField() perc_level = models.IntegerField() date_update = models.DateTimeField(default=datetime.now, blank=True) rank = models.IntegerField(default=0) total = models.IntegerField(default=0) points = models.IntegerField(default=0) last_trophy = models.ForeignKey(userLastTrophy, default=0) I have this query : select t2.user_id as id, t2.platinum - t1.platinum as plat, t2.gold - t1.gold as gold, t2.silver - t1.silver as silver, t2.bronze - t1.bronze as bronze, t2.points - t1.points as points from myps3t_usertrophy t2, myps3t_userlasttrophy t1 where t1.id = t2.last_trophy_id order by points; how to do this with django models ?

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  • Django unable to update model

    - by user292652
    i have the following function to override the default save function in a model match def save(self, *args, **kwargs): if self.Match_Status == "F": Team.objects.filter(pk=self.Team_one.id).update(Played=F('Played')+1) Team.objects.filter(pk=self.Team_two.id).update(Played=F('Played')+1) if self.Winner !="": Team.objects.filter(pk=self.Winner.id).update(Win=F('Win')+1, Points=F('Points')+3) else: return if self.Match_Status == "D": Team.objects.filter(pk=self.Team_one.id).update(Played=F('Played')+1, Draw = F('Draw')+1, Points=F('Points')+1) Team.objects.filter(pk=self.Team_two.id).update(Played=F('Played')+1, Draw = F('Draw')+1, Points=F('Points')+1) super(Match, self).save(*args, **kwargs) I am able to save the match model just fine but Team model does not seem to be updating at all and no error is being thrown. am i missing some thing here ?

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  • Python: Filter a dictionary

    - by Adam Matan
    Hi, I have a dictionary of points, say: >>> points={'a':(3,4), 'b':(1,2), 'c':(5,5), 'd':(3,3)} I want to create a new dictionary with all the points whose x and y value is smaller than 5, i.e. points 'a', 'b' and 'd'. According to the the book, each dictionary has the items() function, which returns a list of (key, pair) tuple: >>> points.items() [('a', (3, 4)), ('c', (5, 5)), ('b', (1, 2)), ('d', (3, 3))] So I have written this: >>> for item in [i for i in points.items() if i[1][0]<5 and i[1][1]<5]: ... points_small[item[0]]=item[1] ... >>> points_small {'a': (3, 4), 'b': (1, 2), 'd': (3, 3)} Is there a more elegant way? I was expecting Python to have some super-awesome dictionary.filter(f) function... Adam

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  • How would you sample a real-time stream of coordinates to create a Speed Graph?

    - by Andrew Johnson
    I have a GPS device, and I am receiving continuous points, which I store in an array. These points are time stamped. I would like to graph distance/time (speed) vs. distance in real-time; however, I can only plot 50 of the points because of hardware constraints. How would you select points from the array to graph? For example, one algorithm might be to select every Nth point from the array, where N results in 50 points total. Code: float indexModifier = 1; if (MIN(50,track.lastPointIndex) == 50) { indexModifier = track.lastPointIndex/50.0f; } index = ceil(index*indexModifier); Another algorithm might be to keep an array of 50 points, and throw out the point with the least speed change each time you get a new point.

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  • java quaternion 3D rotation implementation

    - by MRM
    I made a method to rotate a list of points using quaternions, but all i get back as output is the same list i gave to rotate on. Maybe i did not understood corectly the math for 3d rotations or my code is not implemented the right way, could you give me a hand? This is the method i use: public static ArrayList<Float> rotation3D(ArrayList<Float> points, double angle, int x, int y, int z) { ArrayList<Float> newpoints = points; for (int i=0;i<points.size();i+=3) { float x_old = points.get(i).floatValue(); float y_old = points.get(i+1).floatValue(); float z_old = points.get(i+2).floatValue(); double[] initial = {1,0,0,0}; double[] total = new double[4]; double[] local = new double[4]; //components for local quaternion //w local[0] = Math.cos(0.5 * angle); //x local[1] = x * Math.sin(0.5 * angle); //y local[2] = y * Math.sin(0.5 * angle); //z local[3] = z * Math.sin(0.5 * angle); //components for final quaternion Q1*Q2 //w = w1w2 - x1x2 - y1y2 - z1z2 total[0] = local[0] * initial[0] - local[1] * initial[1] - local[2] * initial[2] - local[3] * initial[3]; //x = w1x2 + x1w2 + y1z2 - z1y2 total[1] = local[0] * initial[1] + local[1] * initial[0] + local[2] * initial[3] - local[3] * initial[2]; //y = w1y2 - x1z2 + y1w2 + z1x2 total[2] = local[0] * initial[2] - local[1] * initial[3] + local[2] * initial[0] + local[3] * initial[1]; //z = w1z2 + x1y2 - y1x2 + z1w2 total[3] = local[0] * initial[3] + local[1] * initial[2] - local[2] * initial[1] + local[3] * initial[0]; //new x,y,z of the 3d point using rotation matrix made from the final quaternion float x_new = (float)((1 - 2 * total[2] * total[2] - 2 * total[3] * total[3]) * x_old + (2 * total[1] * total[2] - 2 * total[0] * total[3]) * y_old + (2 * total[1] * total[3] + 2 * total[0] * total[2]) * z_old); float y_new = (float) ((2 * total[1] * total[2] + 2 * total[0] * total[3]) * x_old + (1 - 2 * total[1] * total[1] - 2 * total[3] * total[3]) * y_old + (2 * total[2] * total[3] + 2 * total[0] * total[1]) * z_old); float z_new = (float) ((2 * total[1] * total[3] - 2 * total[0] * total[2]) * x_old + (2 * total[2] * total[3] - 2 * total[0] * total[1]) * y_old + (1 - 2 * total[1] * total[1] - 2 * total[2] * total[2]) * z_old); newpoints.set(i, x_new); newpoints.set(i+1, y_new); newpoints.set(i+2, z_new); } return newpoints; } For rotation3D(points, 50, 0, 1, 0) where points is: 0.0, 0.0, -9.0; 0.0, 0.0, -11.0; 20.0, 0.0, -11.0; 20.0, 0.0, -9.0; i get back the same list.

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  • T-SQL: How to make a positive value turn into the equivalent negative value (e.g "10.00" to "-10.00"

    - by RPM1984
    Ok so i have a DECIMAL field called "Score". (e.g 10.00) Now, in my SP, i want to increment/decrement the value of this field in update transactions. So i might want to do this: SET @NewScore = @CurrentScore + @Points Where @Points is the value im going to increment/decrement. Now lets say @Points = 10.00. In a certain scenario, i want 10.00 to become -10.00 So the statement would be translated to: SET @NewScore = @CurrentScore + -10.00 How can i do that? I know its a strange question, but basically i want that statement to be dynamic, in that i dont want to have a different statement for incrementing/decrementing the value. I just want something like this: SET @Points = 10.00 IF @ActivityBeingPerformedIsFoo BEGIN -- SET @Points to be equivalent negative value, (e.g -10.00) END SET @NewScore = @CurrentScore + @Points

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  • How to get all n sets of three consecutives elements in an array or arraylist with a for statement ?

    - by newba
    Hi, I'm trying to do a convex hull approach and the little problem is that I need to get all sets of three consecutive vertices, like this: private void isConvexHull(Ponto[] points) { Arrays.sort(points); for (int i = 0; i <points.length; i++) { isClockWise(points[i],points[i+1],points[i+2]); } //... } I always do something that I don't consider clean code. Could please help me find one or more ways to this? I want it to be circular, i.e., if my fisrt point of the a set is the last element in the array, the 2nd element will be the 3rd in the list and the 3rd in that set will be the the 2nd element in the list, and so on. They must be consecutive, that's all.

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  • How to partition a plane

    - by puls200
    Let's say I have a fixed number (X) of points, e.g. coordinates within a given plane (I think you can call it a 2-D point cloud). These points should be partitioned into Y polygons where Y < X. The polygons should not overlap. It would be wonderful if the polygons were konvex (like a Voronoi diagram). Imagine it like locations forming countries. For example, I have 12 points and want to create 3 polygons with 4 points each. I thought about creating a grid which covers the points. Then iterate across the points, assigning them to the closest grid cells. Maybe I miss the obvious? I am sure there are better solutions. Thanks, Daniel I just found an optimization (kmeans++) .Maybe this will yield better results..

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  • Intersection between sets containing different types of variables

    - by Gacek
    Let's assume we have two collections: List<double> values List<SomePoint> points where SomePoint is a type containing three coordinates of the point: SomePoint { double X; double Y; double Z; } Now, I would like to perform the intersection between these two collections to find out for which points in points the z coordinate is eqal to one of the elements of values I created something like that: HashSet<double> hash = new HashSet<double>(points.Select(p=>p.Z)); hash.IntersectWith(values); var result = new List<SomePoints>(); foreach(var h in hash) result.Add(points.Find(p => p.Z == h)); But it won't return these points for which there is the same Z value, but different X and Y. Is there any better way to do it?

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  • Finding the shortest path between two points on a grid, using Haskell.

    - by esperantist
    This is a problem that I can easily enough solve in a non-functional manner. But solving it in Haskell is giving me big problems. Me being inexperienced when it comes to functional programming is surely a reason. The problem: I have a 2D field divided into rectangles of equal size. A simple grid. Some rectangles are empty space (and can be passed through) while others are impassable. Given a starting rectangle A and a destination rectangle B, how would I calculate the shortest path between the two? Movement is possible only vertically and horizontally, in steps a single rectangle large. How would I go about accomplishing this in Haskell? Code snippets certainly welcome, but also certainly not neccessary. And links to further resources also very welcome! Thanks!

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  • Why does division yield a vastly different result than multiplication by a fraction in floating points.

    - by Avram
    I understand why floating point numbers can't be compared, and know about the mantissa and exponent binary representation, but I'm no expert and today I came across something I don't get: Namely lets say you have something like: float denominator, numerator, resultone, resulttwo; resultone = numerator / denominator; float buff = 1 / denominator; resulttwo = numerator * buff; To my knowledge different flops can yield different results and this is not unusual. But in some edge cases these two results seem to be vastly different. To be more specific in my GLSL code calculating the Beckmann facet slope distribution for the Cook-Torrance lighitng model: float a = 1 / (facetSlopeRMS * facetSlopeRMS * pow(clampedCosHalfNormal, 4)); float b = clampedCosHalfNormal * clampedCosHalfNormal - 1.0; float c = facetSlopeRMS * facetSlopeRMS * clampedCosHalfNormal * clampedCosHalfNormal; facetSlopeDistribution = a * exp(b/c); yields very very different results to float a = (facetSlopeRMS * facetSlopeRMS * pow(clampedCosHalfNormal, 4)); facetDlopeDistribution = exp(b/c) / a; Why does it? The second form of the expression is problematic. If I say try to add the second form of the expression to a color I get blacks, even though the expression should always evaluate to a positive number. Am I getting an infinity? A NaN? if so why?

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  • OpenGL texture on sphere

    - by Cilenco
    I want to create a rolling, textured ball in OpenGL ES 1.0 for Android. With this function I can create a sphere: public Ball(GL10 gl, float radius) { ByteBuffer bb = ByteBuffer.allocateDirect(40000); bb.order(ByteOrder.nativeOrder()); sphereVertex = bb.asFloatBuffer(); points = build(); } private int build() { double dTheta = STEP * Math.PI / 180; double dPhi = dTheta; int points = 0; for(double phi = -(Math.PI/2); phi <= Math.PI/2; phi+=dPhi) { for(double theta = 0.0; theta <= (Math.PI * 2); theta+=dTheta) { sphereVertex.put((float) (raduis * Math.sin(phi) * Math.cos(theta))); sphereVertex.put((float) (raduis * Math.sin(phi) * Math.sin(theta))); sphereVertex.put((float) (raduis * Math.cos(phi))); points++; } } sphereVertex.position(0); return points; } public void draw() { texture.bind(); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, sphereVertex); gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, points); gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); } My problem now is that I want to use this texture for the sphere but then only a black ball is created (of course because the top right corner s black). I use this texture coordinates because I want to use the whole texture: 0|0 0|1 1|1 1|0 That's what I learned from texturing a triangle. Is that incorrect if I want to use it with a sphere? What do I have to do to use the texture correctly?

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  • Merging Two KML Files to Display Them with Different Marker Icons on Google Maps

    - by Maxim Z.
    Let's say that I have two spreadsheets with addresses. I uploaded these spreadsheets into Google Fusion Tables, geocoded the addresses, and exported the results as KML files. Now, I want to take these two KML files and merge them, while maintaining the location data and using it to map the points with Google Maps. Well, I found a way to easily merge the KML files: import both of them into a "My Maps" map with Google Maps! However, my problem is this: when I do that, all of the locations in my data have the same marker icon on the map. From past experience, I know that these markers can be somehow defined inside the KML files. Is it possible to combine these two KML files while giving one's points one marker icon and the other's points another marker icon? Just in case my question is confusing, what I mean, is giving the first set of points blue markers, for example, and the other set of points red markers, so that they can be overlayed.

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  • Drawing a circle in opengl es android, squiggly boundaries

    - by ladiesMan217
    I am new to OpenGL ES and facing a hard time drawing a circle on my GLSurfaceView. Here's what I have so far. the Circle Class public class MyGLBall { private int points=40; private float vertices[]={0.0f,0.0f,0.0f}; private FloatBuffer vertBuff; //centre of circle public MyGLBall(){ vertices=new float[(points+1)*3]; for(int i=3;i<(points+1)*3;i+=3){ double rad=(i*360/points*3)*(3.14/180); vertices[i]=(float)Math.cos(rad); vertices[i+1]=(float) Math.sin(rad); vertices[i+2]=0; } ByteBuffer bBuff=ByteBuffer.allocateDirect(vertices.length*4); bBuff.order(ByteOrder.nativeOrder()); vertBuff=bBuff.asFloatBuffer(); vertBuff.put(vertices); vertBuff.position(0); } public void draw(GL10 gl){ gl.glPushMatrix(); gl.glTranslatef(0, 0, 0); // gl.glScalef(size, size, 1.0f); gl.glColor4f(1.0f,1.0f,1.0f, 1.0f); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertBuff); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, points/2); gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); gl.glPopMatrix(); } } I couldn't retrieve the screenshot of my image but here's what it looks like As you can see the border has crests and troughs thereby renering it squiggly which I do not want. All I want is a simple curve

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  • In Perl, how can a subroutine get a coderef that points to itself?

    - by hillu
    For learning purposes, I am toying around with the idea of building event-driven programs in Perl and noticed that it might be nice if a subroutine that was registered as an event handler could, on failure, just schedule another call to itself for a later time. So far, I have come up with something like this: my $cb; my $try = 3; $cb = sub { my $rc = do_stuff(); if (!$rc && --$try) { schedule_event($cb, 10); # schedule $cb to be called in 10 seconds } else { do_other_stuff; } }; schedule_event($cb, 0); # schedule initial call to $cb to be performed ASAP Is there a way that code inside the sub can access the coderef to that sub so I could do without using an extra variable? I'd like to schedule the initial call like this. schedule_event( sub { ... }, 0); I first thought of using caller(0)[3], but this only gives me a function name, (__ANON__ if there's no name), not a code reference that has a pad attached to it.

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  • How to print the address an ada access variable points to?

    - by georg
    I want to print the address of an access variable (pointer) for debugging purposes. type Node is private; type Node_Ptr is access Node; procedure foo(n: in out Node_Ptr) is package Address_Node is new System.Address_To_Access_Conversions(Node); use Address_Node; begin Put_Line("node at address " & System.Address_Image(To_Address(n))); end foo; Address_Image returns the string representation of an address. System.Address_To_Access_Conversions is a generic package to convert between addresses and access types (see ARM 13.7.2), defined as follows: generic type Object(<>) is limited private; package System.Address_To_Access_Conversions is -- [...] type Object_Pointer is access all Object; -- [...] function To_Address(Value : Object_Pointer) return Address; -- [...] end System.Address_To_Access_Conversions; gnat gives me the following errors for procedure foo defined above: expected type "System.Address_To_Access_Conversions.Object_Pointer" from instance at line... found type "Node_Ptr" defined at ... Object_Pointer ist definied as access all Object. From my understanding the type Object is Node, therefore Object_Ptr is access all Node. What is gnat complaining about? I guess my understanding of Ada generics is flawed and I am not using System.Address_To_Access_Conversions correctly. EDIT: I compiled my code with "gnatmake -gnatG" to see the generic instantiation: package address_node is subtype btree__clear__address_node__object__2 is btree__node; type btree__clear__address_node__object_pointer__2 is access all btree__clear__address_node__object__2; function to_address (value : btree__clear__address_node__object_pointer__2) return system__address; end address_node; btree__node is the mangled name of the type Node as defined above, so I really think the parameter type for to_address() is correct, yet gnat is complaining (see above).

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  • How to write text(using CGContextShowTextAtPoint) on graph x and y-axis intervals points?

    - by Rajendra Bhole
    I developed graph using NSObject class and using CGContext method. The following code displaying dynamically in X and Y-axis intervals, CGContextSetRGBStrokeColor(ctx, 2.0, 2.0, 2.0, 1.0); CGContextSetLineWidth(ctx, 2.0); CGContextMoveToPoint(ctx, 30.0, 200.0); CGContextAddLineToPoint(ctx, 30.0, 440.0); for(float y = 400.0; y >= 200.0; y-=30) { CGContextSetRGBStrokeColor(ctx, 2.0, 2.0, 2.0, 1.0); CGContextMoveToPoint(ctx, 28, y); CGContextAddLineToPoint(ctx, 32, y); CGContextStrokePath(ctx); //CGContextClosePath(ctx); } CGContextMoveToPoint(ctx, 10, 420.0); CGContextAddLineToPoint(ctx, 320, 420.0); //CGContextAddLineToPoint(ctx, 320.0, 420.0); //CGContextStrokePath(ctx); for(float x = 60.0; x <= 260.0; x+=30) { CGContextSetRGBStrokeColor(ctx, 2.0, 2.0, 2.0, 1.0); CGContextMoveToPoint(ctx, x, 418.0); CGContextAddLineToPoint(ctx, x, 422.0); CGContextStrokePath(ctx); CGContextClosePath(ctx); } I want to write the dynamic text on the X and Y-axis lines near the intervals (like X-axis is denoting number of days per week and Y-axis denoting something per someting)? Thanks.

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  • Static libraries, dynamic libraries, DLLs, entry points, headers ... how to get out of this alive?

    - by tunnuz
    Hello, I recently had to program C++ under Windows for an University project, and I'm pretty confused about static and dynamic libraries system, what the compiler needs, what the linker needs, how to build a library ... is there any good document about this out there? I'm pretty confused about the *nix library system as well (so, dylibs, the ar tool, how to compile them ...), can you point a review document about the current library techniques on the various architectures? Note: due to my poor knowledge this message could contain wrong concepts, feel free to edit it. Thank you Feel free to add more reference, I will add them to the summary. References Since most of you posted *nix or Windows specific references I will summarize here the best ones, I will mark as accepted answer the Wikipedia one, because is a good start point (and has references inside too) to get introduced to this stuff. Program Library Howto (Unix) Dynamic-Link Libraries (from MSDN) (Windows) DLL Information (StackOverflow) (Windows) Programming in C (Unix) An Overview of Compiling and Linking (Windows)

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  • Find all records in database that are within a certain distance of a set of lat and long points

    - by Mike L
    I've seen all the examples and here's what I got so far. my table is simple: schools (table name) - School_ID - lat - long - county - extrainfo here's my code: <?php $con = mysql_connect("xxx","xxx","xxx"); if (!$con) { die('Could not connect: ' . mysql_error()); } else {} mysql_select_db("xxx", $con); $latitude = "36.265541"; $longitude = "-119.207153"; $distance = "1"; //miles $qry = "SELECT *, (3958.75 * ACOS(SIN(" . $latitude . " / 57.2958)*SIN(lat / 57.2958)+COS(" . $latitude . " / 57.2958)*COS(lat / 57.2958)*COS(long / 57.2958 - " . $longitude . " / 57.2958))) as distance FROM schools WHERE (3958.75 * ACOS(SIN(" . $latitude . " / 57.2958)*SIN(lat / 57.2958)+COS(" . $latitude . " / 57.2958)*COS(lat / 57.2958)*COS(long / 57.2958 - " . $longitude . " / 57.2958))) <= " . $distance; $results = mysql_query($qry); if (mysql_num_rows($results) > 0) { while($row = mysql_fetch_assoc($results)) { print_r($row); } } else {} mysql_close($con); ?> but I get this error when I try to run it: Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource

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  • database design help for game / user levels / progress

    - by sprugman
    Sorry this got long and all prose-y. I'm creating my first truly gamified web app and could use some help thinking about how to structure the data. The Set-up Users need to accomplish tasks in each of several categories before they can move up a level. I've got my Users, Tasks, and Categories tables, and a UserTasks table which joins the three. ("User 3 has added Task 42 in Category 8. Now they've completed it.") That's all fine and working wonderfully. The Challenge I'm not sure of the best way to track the progress in the individual categories toward each level. The "business" rules are: You have to achieve a certain number of points in each category to move up. If you get the number of points needed in Cat 8, but still have other work to do to complete the level, any new Cat 8 points count toward your overall score, but don't "roll over" into the next level. The number of Categories is small (five currently) and unlikely to change often, but by no means absolutely fixed. The number of points needed to level-up will vary per level, probably by a formula, or perhaps a lookup table. So the challenge is to track each user's progress toward the next level in each category. I've thought of a few potential approaches: Possible Solutions Add a column to the users table for each category and reset them all to zero each time a user levels-up. Have a separate UserProgress table with a row for each category for each user and the number of points they have. (Basically a Many-to-Many version of #1.) Add a userLevel column to the UserTasks table and use that to derive their progress with some kind of SUM statement. Their current level will be a simple int in the User table. Pros & Cons (1) seems like by far the most straightforward, but it's also the least flexible. Perhaps I could use a naming convention based on the category ids to help overcome some of that. (With code like "select cats; for each cat, get the value from Users.progress_{cat.id}.") It's also the one where I lose the most data -- I won't know which points counted toward leveling up. I don't have a need in mind for that, so maybe I don't care about that. (2) seems complicated: every time I add or subtract a user or a category, I have to maintain the other table. I foresee synchronization challenges. (3) Is somewhere in between -- cleaner than #2, but less intuitive than #1. In order to find out where a user is, I'd have mildly complex SQL like: SELECT categoryId, SUM(points) from UserTasks WHERE userId={user.id} & countsTowardLevel={user.level} groupBy categoryId Hmm... that doesn't seem so bad. I think I'm talking myself into #3 here, but would love any input, advice or other ideas. P.S. Sorry for the cross-post. I wrote this up on SO and then remembered that there was a game dev-focused one. Curious to see if I get different answers one place than the other....

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  • Best way to enter numeric values with decimal points?

    - by Andrew Grant
    In my app users need to be able to enter numeric values with decimal places. The iPhone doesn't provides a keyboard that's specific for this purpose - only a number pad and a keyboard with numbers and symbols. Is there an easy way to use the latter and prevent any non-numeric input from being entered without having to regex the final result? Thanks!

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