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  • Segmentation fault on returning from main (very short and simple code, no arrays or pointers)

    - by Gábor Kovács
    I've been wondering why the following trivial code produces a segmentation fault when returning from main(): //Produces "Error while dumping state (probably corrupted stack); Segmentation fault" #include <iostream> #include <fstream> #include <vector> using namespace std; class Test { vector<int> numbers; }; int main() { Test a; ifstream infile; cout << "Last statement..." << endl; // this gets executed return 0; } Interestingly, 1) if only one of the two variables is declared, I don't get the error, 2) if I declare a vector variable instead of an object with a vector member, everything's fine, 3) if I declare an ofstream instead of an ifstream, again, everything works fine. Something appears to be wrong with this specific combination... Could this be a compiler bug? I use gcc version 3.4.4 with cygwin. Thanks for the tips in advance. Gábor

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  • Which C++ Standard Library wrapper functions do you use?

    - by Neil Butterworth
    This question, asked this morning, made me wonder which features you think are missing from the C++ Standard Library, and how you have gone about filling the gaps with wrapper functions. For example, my own utility library has this function for vector append: template <class T> std::vector<T> & operator += ( std::vector<T> & v1, const std::vector <T> & v2 ) { v1.insert( v1.end(), v2.begin(), v2.end() ); return v1; } and this one for clearing (more or less) any type - particularly useful for things like std::stack: template <class C> void Clear( C & c ) { c = C(); } I have a few more, but I'm interested in which ones you use? Please limit answers to wrapper functions - i.e. no more than a couple of lines of code.

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  • How to identify multiple identical pairs in two vectors

    - by Sacha Epskamp
    In my graph-package (as in graph theory, nodes connected by edges) I have a vector indicating for each edge the node of origin from, a vector indicating for each edge the node of destination to and a vector indicating the curve of each edge curve. By default I want edges to have a curve of 0 if there is only one edge between two nodes and curve of 0.2 if there are two edges between two nodes. The code that I use now is a for-loop, and it is kinda slow: curve <- rep(0,5) from<-c(1,2,3,3,2) to<-c(2,3,4,2,1) for (i in 1:length(from)) { if (any(from==to[i] & to==from[i])) { curve[i]=0.2 } } So basically I look for each edge (one index in from and one in to) if there is any other pair in from and to that use the same nodes (numbers). What I am looking for are two things: A way to identify if there is any pair of nodes that have two edges between them (so I can omit the loop if not) A way to speed up this loop # EDIT: To make this abit clearer, another example: from <- c(4L, 6L, 7L, 8L, 1L, 9L, 5L, 1L, 2L, 1L, 10L, 2L, 6L, 7L, 10L, 4L, 9L) to <- c(1L, 1L, 1L, 2L, 3L, 3L, 4L, 5L, 6L, 7L, 7L, 8L, 8L, 8L, 8L, 10L, 10L) cbind(from,to) from to [1,] 4 1 [2,] 6 1 [3,] 7 1 [4,] 8 2 [5,] 1 3 [6,] 9 3 [7,] 5 4 [8,] 1 5 [9,] 2 6 [10,] 1 7 [11,] 10 7 [12,] 2 8 [13,] 6 8 [14,] 7 8 [15,] 10 8 [16,] 4 10 [17,] 9 10 In these two vectors, pair 3 is identical to pair 10 (both 1 and 7 in different orders) and pairs 4 and 12 are identical (both 2 and 8). So I would want curve to become: [1,] 0.0 [2,] 0.0 [3,] 0.2 [4,] 0.2 [5,] 0.0 [6,] 0.0 [7,] 0.0 [8,] 0.0 [9,] 0.0 [10,] 0.2 [11,] 0.0 [12,] 0.2 [13,] 0.0 [14,] 0.0 [15,] 0.0 [16,] 0.0 [17,] 0.0 (as I vector, I transposed twice to get row numbers).

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  • Typedef equivalence in function arguments

    - by Warren Seine
    Hi guys, The question is kind of hard to ask without an example so here it is: #include <vector> struct O { }; struct C { template <typename T> void function1(void (C::*callback)(const O*)); template <typename T> void function2(void (C::*callback)(const typename T::value_type)); void print(const O*); }; int main() { C c; c.function1< std::vector<O*> >(&C::print); // Success. c.function2< std::vector<O*> >(&C::print); // Fail. } The error that I am given is: error: no matching function for call to ‘C::function2(void (C::*)(const O*))’. Basically, the only difference between calls is that in function2, I'm more generic since I use the typedef std::vector<O*>::value_type which should resolve to O*, hence similar to function1. I'm using G++ 4.2.1 (I know it's old), but Comeau confirms I'm wrong. Why does the compilation fail?

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  • c++ push_back doesn't work as it is supposed

    - by angela
    I have a class symbol_table that has a vector of objects of another class row_st.also I have an enter method where inserts objects of row_st with a passed name into the vector of desired symbol_table.but when I call the enter to enter objects with name : a;b;c;Iwill get the following result: a,b,c;b,c;c.the first element of vector gets the name of all the entered objects. and the second element also gets the name of the later entries. class row_st { public: char* name; type_u type;//int:0,flaot:1;char:2,bool:3,array: int offset; symbol_table *next; symbol_table *current; }; class symbol_table { public: vector <row_st *> row; int type; int header; int starting_stmt; int index; int i; symbol_table *previous; symbol_table(){ header=0; previous=0; index=0;i=0;starting_stmt=0;} }; and here it is the enter method: int enter(symbol_table *table,char* name,type_u type){ row_st *t=new row_st; t->name=name; t->type=type; t->offset=table->index; t->current=table; table->index++; t->next=0; table->row.push_back(t); table->header +=1; return table->row.size()-1; } the push_backed elements all points to the same address.the new call makes the same row_st every time it is called.what should I do?

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  • Pointers into elements in a container

    - by Pillsy
    Say I have an object: struct Foo { int bar_; Foo(int bar) bar_(bar) {} }; and I have an STL container that contains Foos, perhaps a vector, and I take // Elsewhere... vector<Foo> vec; vec.push_back(Foo(4)); int *p = &(vec[0].bar_) This is a terrible idea, right? The reason is that vector is going to be storing its elements in a dynamically allocated array somewhere, and eventually, if you add enough elements, it will have to allocate another array, copy over all the elements of the original array, and delete the old array. After that happens, p points to garbage. This is why many operations on a vector will invalidate iterators. It seems like it would be reasonable to assume that an operation that would invalidate iterators from a container will also invalidate pointers to data members of container elements, and that if an operation doesn't invalidate iterators, those pointers will still be safe. However, many reasonable assumptions are false. Is this one of them?

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  • Relating text fields to check boxes in Java

    - by Finzz
    This program requires the user to login and request a database to access. The program then gets a connection object, searches through the database storing the column names into a vector for later use. The problem comes with implementing text fields to allow the user to search for specific values within the database. I can get the check boxes and text fields to appear using a gridlayout and add them to a panel. How do I relate the text fields to their appropriate check box? I've tried adding them to a vector, but then they can't also be added to the panel as well. I've searched for a way to name the text fields as the loop cycles through the column names, but it seems impossible to do without having them declared ahead of time. This can't be done either, as it's impossible to determine the attributes that the user will request. I just need to be able to know the names of the text fields so I can test to see if the user entered information and perform the necessary logic. Let me know if you have to see the rest of the code to give an answer, but hopefully you get the general idea of what I'm trying to accomplish. Picture of UI: try { ResultSet r2 = con.getMetaData().getColumns("", "", rb.getText(), ""); colNames1 = new Vector<String>(); columns1 = new Vector<JCheckBox>(); while (r2.next()) { colNames1.add(r2.getString(4)); JCheckBox cb = new JCheckBox(r2.getString(4)); JTextField tf = new JTextField(10); columns1.add(cb); p3.add(cb); p3.add(tf); } }

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  • CSV Parser works in windows, not linux.

    - by ladookie
    I'm parsing a CSV file that looks like this: E1,E2,E7,E8,,, E2,E1,E3,,,, E3,E2,E8,,, E4,E5,E8,E11,,, I store the first entry in each line in a string, and the rest go in a vector of strings: while (getline(file_input, line)) { stringstream tokenizer; tokenizer << line; getline(tokenizer, roomID, ','); vector<string> aVector; while (getline(tokenizer, adjRoomID, ',')) { if (!adjRoomID.empty()) { aVector.push_back(adjRoomID); } } Room aRoom(roomID, aVector); rooms.addToTail(aRoom); } In windows this works fine, however in Linux the first entry of each vector mysteriously loses the first character. For Example in the first iteration through the while loop: roomID would be E1 and aVector would be 2 E7 E8 then the second iteration: roomID would be E2 and aVector would be 1 E3 Notice the missing E's in the first entry of aVector. when I put in some debugging code it appears that it is initially being stored correctly in the vector, but then something overwrites it. Kudos to whoever figures this one out. Seems bizarre to me. rooms is declared as such: DLList<Room> rooms where DLList stands for Doubly-Linked list.

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  • how to create a array of labelfields

    - by sheetal_r oswal
    I have 'n' number of data which has to be added to a label field which in turn has to be added to hfm.I am setting the single data in to label field as : final LabelField desc = new LabelField("", LabelField.FOCUSABLE); final LabelField desc1 = new LabelField("", LabelField.FOCUSABLE); Vector data = (Vector) listEvent.get(keys); for (int i = 0; i < data.size(); i++) { EventData ee = (EventData) data.elementAt(i); String Summary= ee.getSummary(); if (time.getText().equals(sTime)) { desc.setText(Summary); } else{ desc1.setText(Summary); } } HorizontalFieldManager horizontalFieldManager_left18 = new HorizontalFieldManager() { horizontalFieldManager_left18.add(desc1); vfm.add(horizontalFieldManager_left18); vfm.add(new SeparatorField()); HorizontalFieldManager horizontalFieldManager_left17 = new HorizontalFieldManager() { horizontalFieldManager_left17.add(desc); vfm.add(horizontalFieldManager_left17); vfm.add(new SeparatorField()); In the above code i loop over vector and set the data into labelfield and adding the label to hfm later. Now the case is the vector data has more than one summary data,and the data is getting overridden in labelfield,i need to keep 'n' number of summary data into lablefield and add to new hfm.

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  • What would the destructor for this class look like?

    - by cam
    class Equipment { std::vector<Armor*> vEquip; Weapon* mainWeapon; int totalDefense; int totalAttack; public: unsigned int GetWeight(); int * GetDefense(); bool EquipArmor(Armor* armor); bool UnequipArmor(Armor* armor); bool EquipWeapon(Weapon* wep); bool UnequipWeapon(Weapon* wep); Equipment(); virtual ~Equipment(); }; It seems like there should be no destructor. The vector of pointers will take care of itself when it goes out of scope, and the actual objects the pointers point to don't need to be deleted as there will be other references to it. All of the objects in this refer to the main Container: class Container { int weightLimit; unsigned int currWeight; std::vector<Item*> vItems; public: bool AddItem(Item* item); bool RemoveItem(Item* item); Container(); Container(int weightLim); Container(int weightLim, std::vector<Item*> items); ~Container(); }; Now here I can see it being necessary to delete all objects in the container, because this is where all the objects are assigned via AddItem(new Item("Blah")) (Armor and Weapon inherit from Item)

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  • A New Threat To Web Applications: Connection String Parameter Pollution (CSPP)

    - by eric.maurice
    Hi, this is Shaomin Wang. I am a security analyst in Oracle's Security Alerts Group. My primary responsibility is to evaluate the security vulnerabilities reported externally by security researchers on Oracle Fusion Middleware and to ensure timely resolution through the Critical Patch Update. Today, I am going to talk about a serious type of attack: Connection String Parameter Pollution (CSPP). Earlier this year, at the Black Hat DC 2010 Conference, two Spanish security researchers, Jose Palazon and Chema Alonso, unveiled a new class of security vulnerabilities, which target insecure dynamic connections between web applications and databases. The attack called Connection String Parameter Pollution (CSPP) exploits specifically the semicolon delimited database connection strings that are constructed dynamically based on the user inputs from web applications. CSPP, if carried out successfully, can be used to steal user identities and hijack web credentials. CSPP is a high risk attack because of the relative ease with which it can be carried out (low access complexity) and the potential results it can have (high impact). In today's blog, we are going to first look at what connection strings are and then review the different ways connection string injections can be leveraged by malicious hackers. We will then discuss how CSPP differs from traditional connection string injection, and the measures organizations can take to prevent this kind of attacks. In web applications, a connection string is a set of values that specifies information to connect to backend data repositories, in most cases, databases. The connection string is passed to a provider or driver to initiate a connection. Vendors or manufacturers write their own providers for different databases. Since there are many different providers and each provider has multiple ways to make a connection, there are many different ways to write a connection string. Here are some examples of connection strings from Oracle Data Provider for .Net/ODP.Net: Oracle Data Provider for .Net / ODP.Net; Manufacturer: Oracle; Type: .NET Framework Class Library: - Using TNS Data Source = orcl; User ID = myUsername; Password = myPassword; - Using integrated security Data Source = orcl; Integrated Security = SSPI; - Using the Easy Connect Naming Method Data Source = username/password@//myserver:1521/my.server.com - Specifying Pooling parameters Data Source=myOracleDB; User Id=myUsername; Password=myPassword; Min Pool Size=10; Connection Lifetime=120; Connection Timeout=60; Incr Pool Size=5; Decr Pool Size=2; There are many variations of the connection strings, but the majority of connection strings are key value pairs delimited by semicolons. Attacks on connection strings are not new (see for example, this SANS White Paper on Securing SQL Connection String). Connection strings are vulnerable to injection attacks when dynamic string concatenation is used to build connection strings based on user input. When the user input is not validated or filtered, and malicious text or characters are not properly escaped, an attacker can potentially access sensitive data or resources. For a number of years now, vendors, including Oracle, have created connection string builder class tools to help developers generate valid connection strings and potentially prevent this kind of vulnerability. Unfortunately, not all application developers use these utilities because they are not aware of the danger posed by this kind of attacks. So how are Connection String parameter Pollution (CSPP) attacks different from traditional Connection String Injection attacks? First, let's look at what parameter pollution attacks are. Parameter pollution is a technique, which typically involves appending repeating parameters to the request strings to attack the receiving end. Much of the public attention around parameter pollution was initiated as a result of a presentation on HTTP Parameter Pollution attacks by Stefano Di Paola and Luca Carettoni delivered at the 2009 Appsec OWASP Conference in Poland. In HTTP Parameter Pollution attacks, an attacker submits additional parameters in HTTP GET/POST to a web application, and if these parameters have the same name as an existing parameter, the web application may react in different ways depends on how the web application and web server deal with multiple parameters with the same name. When applied to connections strings, the rule for the majority of database providers is the "last one wins" algorithm. If a KEYWORD=VALUE pair occurs more than once in the connection string, the value associated with the LAST occurrence is used. This opens the door to some serious attacks. By way of example, in a web application, a user enters username and password; a subsequent connection string is generated to connect to the back end database. Data Source = myDataSource; Initial Catalog = db; Integrated Security = no; User ID = myUsername; Password = XXX; In the password field, if the attacker enters "xxx; Integrated Security = true", the connection string becomes, Data Source = myDataSource; Initial Catalog = db; Integrated Security = no; User ID = myUsername; Password = XXX; Intergrated Security = true; Under the "last one wins" principle, the web application will then try to connect to the database using the operating system account under which the application is running to bypass normal authentication. CSPP poses serious risks for unprepared organizations. It can be particularly dangerous if an Enterprise Systems Management web front-end is compromised, because attackers can then gain access to control panels to configure databases, systems accounts, etc. Fortunately, organizations can take steps to prevent this kind of attacks. CSPP falls into the Injection category of attacks like Cross Site Scripting or SQL Injection, which are made possible when inputs from users are not properly escaped or sanitized. Escaping is a technique used to ensure that characters (mostly from user inputs) are treated as data, not as characters, that is relevant to the interpreter's parser. Software developers need to become aware of the danger of these attacks and learn about the defenses mechanism they need to introduce in their code. As well, software vendors need to provide templates or classes to facilitate coding and eliminate developers' guesswork for protecting against such vulnerabilities. Oracle has introduced the OracleConnectionStringBuilder class in Oracle Data Provider for .NET. Using this class, developers can employ a configuration file to provide the connection string and/or dynamically set the values through key/value pairs. It makes creating connection strings less error-prone and easier to manager, and ultimately using the OracleConnectionStringBuilder class provides better security against injection into connection strings. For More Information: - The OracleConnectionStringBuilder is located at http://download.oracle.com/docs/cd/B28359_01/win.111/b28375/OracleConnectionStringBuilderClass.htm - Oracle has developed a publicly available course on preventing SQL Injections. The Server Technologies Curriculum course "Defending Against SQL Injection Attacks!" is located at http://st-curriculum.oracle.com/tutorial/SQLInjection/index.htm - The OWASP web site also provides a number of useful resources. It is located at http://www.owasp.org/index.php/Main_Page

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  • Movement prediction for non-shooters

    - by ShadowChaser
    I'm working on an isometric 2D game with moderate-scale multiplayer, approximately 20-30 players connected at once to a persistent server. I've had some difficulty getting a good movement prediction implementation in place. Physics/Movement The game doesn't have a true physics implementation, but uses the basic principles to implement movement. Rather than continually polling input, state changes (ie/ mouse down/up/move events) are used to change the state of the character entity the player is controlling. The player's direction (ie/ north-east) is combined with a constant speed and turned into a true 3D vector - the entity's velocity. In the main game loop, "Update" is called before "Draw". The update logic triggers a "physics update task" that tracks all entities with a non-zero velocity uses very basic integration to change the entities position. For example: entity.Position += entity.Velocity.Scale(ElapsedTime.Seconds) (where "Seconds" is a floating point value, but the same approach would work for millisecond integer values). The key point is that no interpolation is used for movement - the rudimentary physics engine has no concept of a "previous state" or "current state", only a position and velocity. State Change and Update Packets When the velocity of the character entity the player is controlling changes, a "move avatar" packet is sent to the server containing the entity's action type (stand, walk, run), direction (north-east), and current position. This is different from how 3D first person games work. In a 3D game the velocity (direction) can change frame to frame as the player moves around. Sending every state change would effectively transmit a packet per frame, which would be too expensive. Instead, 3D games seem to ignore state changes and send "state update" packets on a fixed interval - say, every 80-150ms. Since speed and direction updates occur much less frequently in my game, I can get away with sending every state change. Although all of the physics simulations occur at the same speed and are deterministic, latency is still an issue. For that reason, I send out routine position update packets (similar to a 3D game) but much less frequently - right now every 250ms, but I suspect with good prediction I can easily boost it towards 500ms. The biggest problem is that I've now deviated from the norm - all other documentation, guides, and samples online send routine updates and interpolate between the two states. It seems incompatible with my architecture, and I need to come up with a better movement prediction algorithm that is closer to a (very basic) "networked physics" architecture. The server then receives the packet and determines the players speed from it's movement type based on a script (Is the player able to run? Get the player's running speed). Once it has the speed, it combines it with the direction to get a vector - the entity's velocity. Some cheat detection and basic validation occurs, and the entity on the server side is updated with the current velocity, direction, and position. Basic throttling is also performed to prevent players from flooding the server with movement requests. After updating its own entity, the server broadcasts an "avatar position update" packet to all other players within range. The position update packet is used to update the client side physics simulations (world state) of the remote clients and perform prediction and lag compensation. Prediction and Lag Compensation As mentioned above, clients are authoritative for their own position. Except in cases of cheating or anomalies, the client's avatar will never be repositioned by the server. No extrapolation ("move now and correct later") is required for the client's avatar - what the player sees is correct. However, some sort of extrapolation or interpolation is required for all remote entities that are moving. Some sort of prediction and/or lag-compensation is clearly required within the client's local simulation / physics engine. Problems I've been struggling with various algorithms, and have a number of questions and problems: Should I be extrapolating, interpolating, or both? My "gut feeling" is that I should be using pure extrapolation based on velocity. State change is received by the client, client computes a "predicted" velocity that compensates for lag, and the regular physics system does the rest. However, it feels at odds to all other sample code and articles - they all seem to store a number of states and perform interpolation without a physics engine. When a packet arrives, I've tried interpolating the packet's position with the packet's velocity over a fixed time period (say, 200ms). I then take the difference between the interpolated position and the current "error" position to compute a new vector and place that on the entity instead of the velocity that was sent. However, the assumption is that another packet will arrive in that time interval, and it's incredibly difficult to "guess" when the next packet will arrive - especially since they don't all arrive on fixed intervals (ie/ state changes as well). Is the concept fundamentally flawed, or is it correct but needs some fixes / adjustments? What happens when a remote player stops? I can immediately stop the entity, but it will be positioned in the "wrong" spot until it moves again. If I estimate a vector or try to interpolate, I have an issue because I don't store the previous state - the physics engine has no way to say "you need to stop after you reach position X". It simply understands a velocity, nothing more complex. I'm reluctant to add the "packet movement state" information to the entities or physics engine, since it violates basic design principles and bleeds network code across the rest of the game engine. What should happen when entities collide? There are three scenarios - the controlling player collides locally, two entities collide on the server during a position update, or a remote entity update collides on the local client. In all cases I'm uncertain how to handle the collision - aside from cheating, both states are "correct" but at different time periods. In the case of a remote entity it doesn't make sense to draw it walking through a wall, so I perform collision detection on the local client and cause it to "stop". Based on point #2 above, I might compute a "corrected vector" that continually tries to move the entity "through the wall" which will never succeed - the remote avatar is stuck there until the error gets too high and it "snaps" into position. How do games work around this?

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  • How to implement smooth flocking

    - by Craig
    I'm working on a simple survival game, avoid the big guy and chase the the small guys to stay alive for as long as possible. I have taken the chase and evade example from MSDN create and drawn 20 mice on the screen. I want the small guys to flock when they arent evading. They are doing this, but it isnt as smooth as I would like it to be. How do i make the movement smoother? Its very jittery.# Below is what I have going at the moment, flocking code is within the IF statement, when it isnt set to evading. Any help would be greatly appreciated! :) namespace ChaseAndEvade { class MouseSprite { public enum MouseAiState { // evading the cat Evading, // the mouse can't see the "cat", and it's wandering around. Wander } // how fast can the mouse move? public float MaxMouseSpeed = 4.5f; // and how fast can it turn? public float MouseTurnSpeed = 0.20f; // MouseEvadeDistance controls the distance at which the mouse will flee from // cat. If the mouse is further than "MouseEvadeDistance" pixels away, he will // consider himself safe. public float MouseEvadeDistance = 100.0f; // this constant is similar to TankHysteresis. The value is larger than the // tank's hysteresis value because the mouse is faster than the tank: with a // higher velocity, small fluctuations are much more visible. public float MouseHysteresis = 60.0f; public Texture2D mouseTexture; public Vector2 mouseTextureCenter; public Vector2 mousePosition; public MouseAiState mouseState = MouseAiState.Wander; public float mouseOrientation; public Vector2 mouseWanderDirection; int separationImpact = 4; int cohesionImpact = 6; int alignmentImpact = 2; int sensorDistance = 50; public void UpdateMouse(Vector2 position, MouseSprite [] mice, int numberMice, int index) { Vector2 catPosition = position; int enemies = numberMice; // first, calculate how far away the mouse is from the cat, and use that // information to decide how to behave. If they are too close, the mouse // will switch to "active" mode - fleeing. if they are far apart, the mouse // will switch to "idle" mode, where it roams around the screen. // we use a hysteresis constant in the decision making process, as described // in the accompanying doc file. float distanceFromCat = Vector2.Distance(mousePosition, catPosition); // the cat is a safe distance away, so the mouse should idle: if (distanceFromCat > MouseEvadeDistance + MouseHysteresis) { mouseState = MouseAiState.Wander; } // the cat is too close; the mouse should run: else if (distanceFromCat < MouseEvadeDistance - MouseHysteresis) { mouseState = MouseAiState.Evading; } // if neither of those if blocks hit, we are in the "hysteresis" range, // and the mouse will continue doing whatever it is doing now. // the mouse will move at a different speed depending on what state it // is in. when idle it won't move at full speed, but when actively evading // it will move as fast as it can. this variable is used to track which // speed the mouse should be moving. float currentMouseSpeed; // the second step of the Update is to change the mouse's orientation based // on its current state. if (mouseState == MouseAiState.Evading) { // If the mouse is "active," it is trying to evade the cat. The evasion // behavior is accomplished by using the TurnToFace function to turn // towards a point on a straight line facing away from the cat. In other // words, if the cat is point A, and the mouse is point B, the "seek // point" is C. // C // B // A Vector2 seekPosition = 2 * mousePosition - catPosition; // Use the TurnToFace function, which we introduced in the AI Series 1: // Aiming sample, to turn the mouse towards the seekPosition. Now when // the mouse moves forward, it'll be trying to move in a straight line // away from the cat. mouseOrientation = ChaseAndEvadeGame.TurnToFace(mousePosition, seekPosition, mouseOrientation, MouseTurnSpeed); // set currentMouseSpeed to MaxMouseSpeed - the mouse should run as fast // as it can. currentMouseSpeed = MaxMouseSpeed; } else { // if the mouse isn't trying to evade the cat, it should just meander // around the screen. we'll use the Wander function, which the mouse and // tank share, to accomplish this. mouseWanderDirection and // mouseOrientation are passed by ref so that the wander function can // modify them. for more information on ref parameters, see // http://msdn2.microsoft.com/en-us/library/14akc2c7(VS.80).aspx ChaseAndEvadeGame.Wander(mousePosition, ref mouseWanderDirection, ref mouseOrientation, MouseTurnSpeed); // if the mouse is wandering, it should only move at 25% of its maximum // speed. currentMouseSpeed = .25f * MaxMouseSpeed; Vector2 separate = Vector2.Zero; Vector2 moveCloser = Vector2.Zero; Vector2 moveAligned = Vector2.Zero; // What the AI does when it sees other AIs for (int j = 0; j < enemies; j++) { if (index != j) { // Calculate a vector towards another AI Vector2 separation = mice[index].mousePosition - mice[j].mousePosition; // Only react if other AI is within a certain distance if ((separation.Length() < this.sensorDistance) & (separation.Length()> 0) ) { moveAligned += mice[j].mouseWanderDirection; float distance = Math.Abs(separation.Length()); if (distance == 0) distance = 1; moveCloser += mice[j].mousePosition; separation.Normalize(); separate += separation / distance; } } } if (moveAligned.LengthSquared() != 0) { moveAligned.Normalize(); } if (moveCloser.LengthSquared() != 0) { moveCloser.Normalize(); } moveCloser /= enemies; mice[index].mousePosition += (separate * separationImpact) + (moveCloser * cohesionImpact) + (moveAligned * alignmentImpact); } // The final step is to move the mouse forward based on its current // orientation. First, we construct a "heading" vector from the orientation // angle. To do this, we'll use Cosine and Sine to tell us the x and y // components of the heading vector. See the accompanying doc for more // information. Vector2 heading = new Vector2( (float)Math.Cos(mouseOrientation), (float)Math.Sin(mouseOrientation)); // by multiplying the heading and speed, we can get a velocity vector. the // velocity vector is then added to the mouse's current position, moving him // forward. mousePosition += heading * currentMouseSpeed; } } }

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  • program crashes at CIN input | C++

    - by TimothyTech
    hello okay, so i made a DOS program however my game always crashes on my second time running to the cin function. #include <iostream> #include <string> #include <ctime> #include <cstdlib> using namespace std; //call functions int create_enemyHP (int a); int create_enemyAtk (int a); int find_Enemy(int a); int create_enemyDef (int a); // user information int userHP = 100; int userAtk = 10; int userDef = 5; string userName; //enemy Information int enemyHP; int enemyAtk; int enemyDef; string enemies[] = {"Raider", "Bandit", "Mugger"}; int sizeOfEnemies = sizeof(enemies) / sizeof(int); string currentEnemy; int chooseEnemy; // ACTIONS int journey; int test; int main() { // main menu cout << "welcome brave knight, what is your name? " ; cin >> userName; cout << "welcome " << userName << " to Darland" << endl; //TRAVELING MENU: cout << "where would you like to travel? " << endl; cout << endl << " 1.> Theives Pass " << endl; cout << " 2.> Humble Town " << endl; cout << " 3.> Mission HQ " << endl; cin >> journey; if (journey == 1) { // action variable; string c_action; cout << "beware your journey grows dangerous " << endl; //begins battle // Creating the enemy, HP ATK DEF AND TYPE. ; srand(time(0)); enemyHP = create_enemyHP(userHP); enemyAtk = create_enemyAtk(userAtk); enemyDef = create_enemyDef(userDef); chooseEnemy = find_Enemy(sizeOfEnemies); currentEnemy = enemies[chooseEnemy]; cout << " Here comes a " << currentEnemy << endl; cout << "stats: " << endl; cout << "HP :" << enemyHP << endl; cout << "Attack : " << enemyAtk << endl; cout << "Defense : " << enemyDef << endl; ACTIONS: cout << "Attack <A> | Defend <D> | Items <I>"; cin >> c_action; //if ATTACK/DEFEND/ITEMS choice if (c_action == "A" || c_action == "a"){ enemyHP = enemyHP - userAtk; cout << " you attack the enemy reducing his health to " << enemyHP << endl; userHP = userHP - enemyAtk; cout << "however he lashes back causing you to have " << userHP << "health left " << endl; //end of ATTACK ACTION } the last line "cin c_action crashes. i use two other pages. they just create the functions. is it a complier issue. also why does my complier always shutdown after it runs he app. is there a way to stop it?

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  • Need help with copy constructor for very basic implementation of singly linked lists

    - by Jesus
    Last week, we created a program that manages sets of strings, using classes and vectors. I was able to complete this 100%. This week, we have to replace the vector we used to store strings in our class with simple singly linked lists. The function basically allows users to declare sets of strings that are empty, and sets with only one element. In the main file, there is a vector whose elements are a struct that contain setName and strSet (class). HERE IS MY PROBLEM: It deals with the copy constructor of the class. When I remove/comment out the copy constructor, I can declare as many empty or single sets as I want, and output their values without a problem. But I know I will obviously need the copy constructor for when I implement the rest of the program. When I leave the copy constructor in, I can declare one set, either single or empty, and output its value. But if I declare a 2nd set, and i try to output either of the first two sets, i get a Segmentation Fault. Moreover, if i try to declare more then 2 sets, I get a Segmentation Fault. Any help would be appreciated!! Here is my code for a very basic implementation of everything: Here is the setcalc.cpp: (main file) #include <iostream> #include <cctype> #include <cstring> #include <string> #include "help.h" #include "strset2.h" using namespace std; // Declares of structure to hold all the sets defined struct setsOfStr { string nameOfSet; strSet stringSet; }; // Checks if the set name inputted is unique bool isSetNameUnique( vector<setsOfStr> strSetArr, string setName) { for(unsigned int i = 0; i < strSetArr.size(); i++) { if( strSetArr[i].nameOfSet == setName ) { return false; } } return true; } int main(int argc, char *argv[]) { char commandChoice; // Declares a vector with our declared structure as the type vector<setsOfStr> strSetVec; string setName; string singleEle; // Sets a loop that will constantly ask for a command until 'q' is typed while (1) { // declaring a set to be empty if(commandChoice == 'd') { cin >> setName; // Check that the set name inputted is unique if (isSetNameUnique(strSetVec, setName) == true) { strSet emptyStrSet; setsOfStr set1; set1.nameOfSet = setName; set1.stringSet = emptyStrSet; strSetVec.push_back(set1); } else { cerr << "ERROR: Re-declaration of set '" << setName << "'\n"; } } // declaring a set to be a singleton else if(commandChoice == 's') { cin >> setName; cin >> singleEle; // Check that the set name inputted is unique if (isSetNameUnique(strSetVec, setName) == true) { strSet singleStrSet(singleEle); setsOfStr set2; set2.nameOfSet = setName; set2.stringSet = singleStrSet; strSetVec.push_back(set2); } else { cerr << "ERROR: Re-declaration of set '" << setName << "'\n"; } } // using the output function else if(commandChoice == 'o') { cin >> setName; if(isSetNameUnique(strSetVec, setName) == false) { // loop through until the set name is matched and call output on its strSet for(unsigned int k = 0; k < strSetVec.size(); k++) { if( strSetVec[k].nameOfSet == setName ) { (strSetVec[k].stringSet).output(); } } } else { cerr << "ERROR: No such set '" << setName << "'\n"; } } // quitting else if(commandChoice == 'q') { break; } else { cerr << "ERROR: Ignoring bad command: '" << commandChoice << "'\n"; } } return 0; } Here is the strSet2.h: #ifndef _STRSET_ #define _STRSET_ #include <iostream> #include <vector> #include <string> struct node { std::string s1; node * next; }; class strSet { private: node * first; public: strSet (); // Create empty set strSet (std::string s); // Create singleton set strSet (const strSet &copy); // Copy constructor // will implement destructor later void output() const; strSet& operator = (const strSet& rtSide); // Assignment }; // End of strSet class #endif // _STRSET_ And here is the strSet2.cpp (implementation of class) #include <iostream> #include <vector> #include <string> #include "strset2.h" using namespace std; strSet::strSet() { first = NULL; } strSet::strSet(string s) { node *temp; temp = new node; temp->s1 = s; temp->next = NULL; first = temp; } strSet::strSet(const strSet& copy) { cout << "copy-cst\n"; node *n = copy.first; node *prev = NULL; while (n) { node *newNode = new node; newNode->s1 = n->s1; newNode->next = NULL; if (prev) { prev->next = newNode; } else { first = newNode; } prev = newNode; n = n->next; } } void strSet::output() const { if(first == NULL) { cout << "Empty set\n"; } else { node *temp; temp = first; while(1) { cout << temp->s1 << endl; if(temp->next == NULL) break; temp = temp->next; } } } strSet& strSet::operator = (const strSet& rtSide) { first = rtSide.first; return *this; }

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  • Friday Fun: Spell Blazer

    - by Asian Angel
    Are you ready for some fun and adventure after a long week back at work? This week’s game combines jewel-matching style game play with an RPG story for an awesome mix of fun and fiction. Your goal is to help a young wizard reach the magic academy in Raven as the forces of darkness are building. Spell Blazer The object of the game is to help young Kaven reach the Lightcaster Academy in Raven alive, but he will encounter many dangers along the way. Are you ready to begin the quest? As soon as you click Start Game the intro will automatically begin. If this is your first time playing the game the intro provides a nice background story for the game and what is happening in the game environment. Once you are past the intro, you will see a map of the region with your starting point in the Farmlands, various towns and the roads connecting them, along with your final destination of Raven. Notice that some of the roads are different colors…those colors indicate the “danger levels” for each part of your journey (green = good, yellow = some danger, etc.). To begin your journey click on the Town of Goose with your mouse. You will encounter your first monster part of the way towards Goose. This first round takes you through the game play process step-by-step. Once you have clicked Okay you will see the details about the monster you have just encountered. It is very important that you do not click on Fight! or Flee! until viewing and noting the types of spells that the monster is resistant to or has a weakness against. Choose your spells wisely based on the information provided about the monster. Keep in mind that the healing spell can be very useful depending on the monster you meet and your current health status. Note: Spells shown in order here are Healing, Fireball, Icebolt, & Lightning. Ready to fight! The first battle will also explain how to fight…click Okay to get started. Once the main window is in full view there are details that you need to look at. Beneath each of the combatants you will see the three attacks that each brings to the battle and at the bottom you will see their respective health points. We got lucky and had an Icebolt attack that we could utilize on the first play! Note: You can exchange two squares without making a match in order to try and line up an attack. While it happened too quickly to capture in our screenshot, there will be cool lightning bolt effects shoot out from matched up squares to the opposite combatant. You will also see the amount of damage inflicted from a particular attack on top of the avatars. Victory! Once you have won a round of combat a window will appear showing the amount of gold coins left behind by the monster. When you reach a town you will have the opportunity to stop over and rest or directly continue on with your journey. On to Halgard after a good rest! Play Spell Blazer Latest Features How-To Geek ETC How To Boot 10 Different Live CDs From 1 USB Flash Drive The 20 Best How-To Geek Linux Articles of 2010 The 50 Best How-To Geek Windows Articles of 2010 The 20 Best How-To Geek Explainer Topics for 2010 How to Disable Caps Lock Key in Windows 7 or Vista How to Use the Avira Rescue CD to Clean Your Infected PC The Deep – Awesome Use of Metal Objects as Deep Sea Creatures [Video] Convert or View Documents Online Easily with Zoho, No Account Required Build a Floor Scrubbing Robot out of Computer Fans and a Frisbee Serene Blue Windows Wallpaper for Your Desktop 2011 International Space Station Calendar Available for Download (Free) Ultimate Elimination – Lego Black Ops [Video]

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  • How to develop RPG Damage Formulas?

    - by user127817
    I'm developing a classical 2d RPG (in a similar vein to final fantasy) and I was wondering if anyone had some advice on how to do damage formulas/links to resources/examples? I'll explain my current setup. Hopefully I'm not overdoing it with this question, and I apologize if my questions is too large/broad My Characters stats are composed of the following: enum Stat { HP = 0, MP = 1, SP = 2, Strength = 3, Vitality = 4, Magic = 5, Spirit = 6, Skill = 7, Speed = 8, //Speed/Agility are the same thing Agility = 8, Evasion = 9, MgEvasion = 10, Accuracy = 11, Luck = 12, }; Vitality is basically defense to physical attacks and spirit is defense to magic attacks. All stats have fixed maximums (9999 for HP, 999 for MP/SP and 255 for the rest). With abilities, the maximums can be increased (99999 for HP, 9999 for HP/SP, 999 for the rest) with typical values (at level 100) before/after abilities+equipment+etc will be 8000/20,000 for HP, 800/2000 for SP/MP, 180/350 for other stats Late game Enemy HP will typically be in the lower millions (with a super boss having the maximum of ~12 million). I was wondering how do people actually develop proper damage formulas that scale correctly? For instance, based on this data, using the damage formulas for Final Fantasy X as a base looked very promising. A full reference here http://www.gamefaqs.com/ps2/197344-final-fantasy-x/faqs/31381 but as a quick example: Str = 127, 'Attack' command used, enemy Def = 34. 1. Physical Damage Calculation: Step 1 ------------------------------------- [{(Stat^3 ÷ 32) + 32} x DmCon ÷16] Step 2 ---------------------------------------- [{(127^3 ÷ 32) + 32} x 16 ÷ 16] Step 3 -------------------------------------- [{(2048383 ÷ 32) + 32} x 16 ÷ 16] Step 4 --------------------------------------------------- [{(64011) + 32} x 1] Step 5 -------------------------------------------------------- [{(64043 x 1)}] Step 6 ---------------------------------------------------- Base Damage = 64043 Step 7 ----------------------------------------- [{(Def - 280.4)^2} ÷ 110] + 16 Step 8 ------------------------------------------ [{(34 - 280.4)^2} ÷ 110] + 16 Step 9 ------------------------------------------------- [(-246)^2) ÷ 110] + 16 Step 10 ---------------------------------------------------- [60516 ÷ 110] + 16 Step 11 ------------------------------------------------------------ [550] + 16 Step 12 ---------------------------------------------------------- DefNum = 566 Step 13 ---------------------------------------------- [BaseDmg * DefNum ÷ 730] Step 14 --------------------------------------------------- [64043 * 566 ÷ 730] Step 15 ------------------------------------------------------ [36248338 ÷ 730] Step 16 ------------------------------------------------- Base Damage 2 = 49655 Step 17 ------------ Base Damage 2 * {730 - (Def * 51 - Def^2 ÷ 11) ÷ 10} ÷ 730 Step 18 ---------------------- 49655 * {730 - (34 * 51 - 34^2 ÷ 11) ÷ 10} ÷ 730 Step 19 ------------------------- 49655 * {730 - (1734 - 1156 ÷ 11) ÷ 10} ÷ 730 Step 20 ------------------------------- 49655 * {730 - (1734 - 105) ÷ 10} ÷ 730 Step 21 ------------------------------------- 49655 * {730 - (1629) ÷ 10} ÷ 730 Step 22 --------------------------------------------- 49655 * {730 - 162} ÷ 730 Step 23 ----------------------------------------------------- 49655 * 568 ÷ 730 Step 24 -------------------------------------------------- Final Damage = 38635 I simply modified the dividers to include the attack rating of weapons and the armor rating of armor. Magic Damage is calculated as follows: Mag = 255, Ultima is used, enemy MDef = 1 Step 1 ----------------------------------- [DmCon * ([Stat^2 ÷ 6] + DmCon) ÷ 4] Step 2 ------------------------------------------ [70 * ([255^2 ÷ 6] + 70) ÷ 4] Step 3 ------------------------------------------ [70 * ([65025 ÷ 6] + 70) ÷ 4] Step 4 ------------------------------------------------ [70 * (10837 + 70) ÷ 4] Step 5 ----------------------------------------------------- [70 * (10907) ÷ 4] Step 6 ------------------------------------ Base Damage = 190872 [cut to 99999] Step 7 ---------------------------------------- [{(MDef - 280.4)^2} ÷ 110] + 16 Step 8 ------------------------------------------- [{(1 - 280.4)^2} ÷ 110] + 16 Step 9 ---------------------------------------------- [{(-279.4)^2} ÷ 110] + 16 Step 10 -------------------------------------------------- [(78064) ÷ 110] + 16 Step 11 ------------------------------------------------------------ [709] + 16 Step 12 --------------------------------------------------------- MDefNum = 725 Step 13 --------------------------------------------- [BaseDmg * MDefNum ÷ 730] Step 14 --------------------------------------------------- [99999 * 725 ÷ 730] Step 15 ------------------------------------------------- Base Damage 2 = 99314 Step 16 ---------- Base Damage 2 * {730 - (MDef * 51 - MDef^2 ÷ 11) ÷ 10} ÷ 730 Step 17 ------------------------ 99314 * {730 - (1 * 51 - 1^2 ÷ 11) ÷ 10} ÷ 730 Step 18 ------------------------------ 99314 * {730 - (51 - 1 ÷ 11) ÷ 10} ÷ 730 Step 19 --------------------------------------- 99314 * {730 - (49) ÷ 10} ÷ 730 Step 20 ----------------------------------------------------- 99314 * 725 ÷ 730 Step 21 -------------------------------------------------- Final Damage = 98633 The problem is that the formulas completely fall apart once stats start going above 255. In particular Defense values over 300 or so start generating really strange behavior. High Strength + Defense stats lead to massive negative values for instance. While I might be able to modify the formulas to work correctly for my use case, it'd probably be easier just to use a completely new formula. How do people actually develop damage formulas? I was considering opening excel and trying to build the formula that way (mapping Attack Stats vs. Defense Stats for instance) but I was wondering if there's an easier way? While I can't convey the full game mechanics of my game here, might someone be able to suggest a good starting place for building a damage formula? Thanks

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  • How to develop RPG Damage Formulas?

    - by user127817
    I'm developing a classical 2d RPG (in a similar vein to final fantasy) and I was wondering if anyone had some advice on how to do damage formulas/links to resources/examples? I'll explain my current setup. Hopefully I'm not overdoing it with this question, and I apologize if my questions is too large/broad My Characters stats are composed of the following: enum Stat { HP = 0, MP = 1, SP = 2, Strength = 3, Vitality = 4, Magic = 5, Spirit = 6, Skill = 7, Speed = 8, //Speed/Agility are the same thing Agility = 8, Evasion = 9, MgEvasion = 10, Accuracy = 11, Luck = 12, }; Vitality is basically defense to physical attacks and spirit is defense to magic attacks. All stats have fixed maximums (9999 for HP, 999 for MP/SP and 255 for the rest). With abilities, the maximums can be increased (99999 for HP, 9999 for HP/SP, 999 for the rest) with typical values (at level 100) before/after abilities+equipment+etc will be 8000/20,000 for HP, 800/2000 for SP/MP, 180/350 for other stats Late game Enemy HP will typically be in the lower millions (with a super boss having the maximum of ~12 million). I was wondering how do people actually develop proper damage formulas that scale correctly? For instance, based on this data, using the damage formulas for Final Fantasy X as a base looked very promising. A full reference here http://www.gamefaqs.com/ps2/197344-final-fantasy-x/faqs/31381 but as a quick example: Str = 127, 'Attack' command used, enemy Def = 34. 1. Physical Damage Calculation: Step 1 ------------------------------------- [{(Stat^3 ÷ 32) + 32} x DmCon ÷16] Step 2 ---------------------------------------- [{(127^3 ÷ 32) + 32} x 16 ÷ 16] Step 3 -------------------------------------- [{(2048383 ÷ 32) + 32} x 16 ÷ 16] Step 4 --------------------------------------------------- [{(64011) + 32} x 1] Step 5 -------------------------------------------------------- [{(64043 x 1)}] Step 6 ---------------------------------------------------- Base Damage = 64043 Step 7 ----------------------------------------- [{(Def - 280.4)^2} ÷ 110] + 16 Step 8 ------------------------------------------ [{(34 - 280.4)^2} ÷ 110] + 16 Step 9 ------------------------------------------------- [(-246)^2) ÷ 110] + 16 Step 10 ---------------------------------------------------- [60516 ÷ 110] + 16 Step 11 ------------------------------------------------------------ [550] + 16 Step 12 ---------------------------------------------------------- DefNum = 566 Step 13 ---------------------------------------------- [BaseDmg * DefNum ÷ 730] Step 14 --------------------------------------------------- [64043 * 566 ÷ 730] Step 15 ------------------------------------------------------ [36248338 ÷ 730] Step 16 ------------------------------------------------- Base Damage 2 = 49655 Step 17 ------------ Base Damage 2 * {730 - (Def * 51 - Def^2 ÷ 11) ÷ 10} ÷ 730 Step 18 ---------------------- 49655 * {730 - (34 * 51 - 34^2 ÷ 11) ÷ 10} ÷ 730 Step 19 ------------------------- 49655 * {730 - (1734 - 1156 ÷ 11) ÷ 10} ÷ 730 Step 20 ------------------------------- 49655 * {730 - (1734 - 105) ÷ 10} ÷ 730 Step 21 ------------------------------------- 49655 * {730 - (1629) ÷ 10} ÷ 730 Step 22 --------------------------------------------- 49655 * {730 - 162} ÷ 730 Step 23 ----------------------------------------------------- 49655 * 568 ÷ 730 Step 24 -------------------------------------------------- Final Damage = 38635 I simply modified the dividers to include the attack rating of weapons and the armor rating of armor. Magic Damage is calculated as follows: Mag = 255, Ultima is used, enemy MDef = 1 Step 1 ----------------------------------- [DmCon * ([Stat^2 ÷ 6] + DmCon) ÷ 4] Step 2 ------------------------------------------ [70 * ([255^2 ÷ 6] + 70) ÷ 4] Step 3 ------------------------------------------ [70 * ([65025 ÷ 6] + 70) ÷ 4] Step 4 ------------------------------------------------ [70 * (10837 + 70) ÷ 4] Step 5 ----------------------------------------------------- [70 * (10907) ÷ 4] Step 6 ------------------------------------ Base Damage = 190872 [cut to 99999] Step 7 ---------------------------------------- [{(MDef - 280.4)^2} ÷ 110] + 16 Step 8 ------------------------------------------- [{(1 - 280.4)^2} ÷ 110] + 16 Step 9 ---------------------------------------------- [{(-279.4)^2} ÷ 110] + 16 Step 10 -------------------------------------------------- [(78064) ÷ 110] + 16 Step 11 ------------------------------------------------------------ [709] + 16 Step 12 --------------------------------------------------------- MDefNum = 725 Step 13 --------------------------------------------- [BaseDmg * MDefNum ÷ 730] Step 14 --------------------------------------------------- [99999 * 725 ÷ 730] Step 15 ------------------------------------------------- Base Damage 2 = 99314 Step 16 ---------- Base Damage 2 * {730 - (MDef * 51 - MDef^2 ÷ 11) ÷ 10} ÷ 730 Step 17 ------------------------ 99314 * {730 - (1 * 51 - 1^2 ÷ 11) ÷ 10} ÷ 730 Step 18 ------------------------------ 99314 * {730 - (51 - 1 ÷ 11) ÷ 10} ÷ 730 Step 19 --------------------------------------- 99314 * {730 - (49) ÷ 10} ÷ 730 Step 20 ----------------------------------------------------- 99314 * 725 ÷ 730 Step 21 -------------------------------------------------- Final Damage = 98633 The problem is that the formulas completely fall apart once stats start going above 255. In particular Defense values over 300 or so start generating really strange behavior. High Strength + Defense stats lead to massive negative values for instance. While I might be able to modify the formulas to work correctly for my use case, it'd probably be easier just to use a completely new formula. How do people actually develop damage formulas? I was considering opening excel and trying to build the formula that way (mapping Attack Stats vs. Defense Stats for instance) but I was wondering if there's an easier way? While I can't convey the full game mechanics of my game here, might someone be able to suggest a good starting place for building a damage formula? Thanks

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  • R strsplit and vectorization

    - by James
    When creating functions that use strsplit, vector inputs do not behave as desired, and sapply needs to be used. This is due to the list output that strsplit produces. Is there a way to vectorize the process - that is, the function produces the correct element in the list for each of the elements of the input? For example, to count the lengths of words in a character vector: words <- c("a","quick","brown","fox") > length(strsplit(words,"")) [1] 4 # The number of words (length of the list) > length(strsplit(words,"")[[1]]) [1] 1 # The length of the first word only > sapply(words,function (x) length(strsplit(x,"")[[1]])) a quick brown fox 1 5 5 3 # Success, but potentially very slow Ideally, something like length(strsplit(words,"")[[.]]) where . is interpreted as the being the relevant part of the input vector.

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  • How to reshape matrices in Mathematica

    - by speciousfool
    When manipulating matrices it is often convenient to change their shape. For instance, to turn an N x M sized matrix into a vector of length N X M. In MATLAB a reshape function exists: RESHAPE(X,M,N) returns the M-by-N matrix whose elements are taken columnwise from X. An error results if X does not have M*N elements. In the case of converting between a matrix and vector I can use the Mathematica function Flatten which takes advantage of Mathematica's nested list representation for matrices. As a quick example, suppose I have a matrix X: With Flatten[X] I can get the vector {1,2,3,...,16}. But what would be far more useful is something akin to applying Matlab's reshape(X,2,8) which would result in the following Matrix: This would allow creation of arbitrary matrices as long as the dimensions equal N*M. As far as I can tell, there isn't anything built in which makes me wonder if someone hasn't coded up a Reshape function of their own.

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  • Marshal struct to unmanaged array

    - by Pedro
    Hi guys, I have a C# struct to represent a cartesian vector, something like this: public struct Vector { private double x; private double y; private double z; //Some properties/methods } Now I have an unmanaged C dll that I need to call with P/Invoke. Some methods expect a double[3] parameter. The unmanaged C signature is something like void Cross(double a[3], double b[3], double c[3]); Is there any way to set up a P/Invoke signature so I can pass instances of my Vector struct and marshal them transparently to unmanaged double[3]? I would also need bidirectional marshaling as the unmanaged function needs to write the output to the argument array, so I guess I would need to marshal as LpArray. Any ideas? Thanks Pedro

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  • Question on multi-probe Local Sensitive Hashing

    - by Yijinsei
    Hey guys sorry to be asking this kind noob question, but because I really need some guidance on how to use Multi probe LSH pretty urgently, so I did not do much research myself. I realize there is a lib call LSHKIT available that implemented that algorithm, but I have trouble trying to figure out how to use it. Right now, I have a few thousand feature vector 296 dimension, each representing an image. The vector is used to query an user input image, to retrieve the most similar image. The method I used to derive the distance between vector is euclidean distance. I know this might be a rather noob question, but do you guys have knowledge on how should i implement multi probe LSH? I am really very grateful to any answer or response.

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  • Java Swing GUI exception - Exception in thread "AWT-EventQueue-0" java.util.NoSuchElementException:

    - by rgksugan
    I get this exception when i run my application. I dont have any idea what is going wrong here. Can someone help please. Exception in thread "AWT-EventQueue-0" java.util.NoSuchElementException: Vector Enumeration at java.util.Vector$1.nextElement(Vector.java:305) at javax.swing.plaf.basic.BasicTableHeaderUI.getPreferredSize(BasicTableHeaderUI.java:778) at javax.swing.JComponent.getPreferredSize(JComponent.java:1634) at javax.swing.ViewportLayout.preferredLayoutSize(ViewportLayout.java:78) at java.awt.Container.preferredSize(Container.java:1599) at java.awt.Container.getPreferredSize(Container.java:1584) at javax.swing.JComponent.getPreferredSize(JComponent.java:1636) at javax.swing.ScrollPaneLayout.layoutContainer(ScrollPaneLayout.java:702) at java.awt.Container.layout(Container.java:1421) at java.awt.Container.doLayout(Container.java:1410) at java.awt.Container.validateTree(Container.java:1507) at java.awt.Container.validate(Container.java:1480) at javax.swing.RepaintManager.validateInvalidComponents(RepaintManager.java:669) at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:124) at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209) at java.awt.EventQueue.dispatchEvent(EventQueue.java:597) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

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  • How to handle value types when embedding IronPython in C#?

    - by kloffy
    There is a well known issue when it comes to using .NET value types in IronPython. This has recently caused me a headache when trying to use Python as an embedded scripting language in C#. The problem can be summed up as follows: Given a C# struct such as: struct Vector { public float x; public float y; } And a C# class such as: class Object { public Vector position; } The following will happen in IronPython: obj = Object() print obj.position.x # prints ‘0’ obj.position.x = 1 print obj.position.x # still prints ‘0’ As the article states, this means that value types are mostly immutable. However, this is a problem as I was planning on using a vector library that is implemented as seen above. Are there any workarounds for working with existing libraries that rely on value types? Modifying the library would be the very last resort, but I'd rather avoid that.

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