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  • Strict pointer aliasing: any solution for a specific problem?

    - by doublep
    I have a problem caused by breaking strict pointer aliasing rule. I have a type T that comes from a template and some integral type Int of the same size (as with sizeof). My code essentially does the following: T x = some_other_t; if (*reinterpret_cast <Int*> (&x) == 0) ... Because T is some arbitary (other than the size restriction) type that could have a constructor, I cannot make a union of T and Int. (This is allowed only in C++0x only and isn't even supported by GCC yet). Is there any way I could rewrite the above pseudocode to preserve functionality and avoid breaking strict aliasing rule? Note that this is a template, I cannot control T or value of some_other_t; the assignment and subsequent comparison do happen inside the templated code. (For the record, the above code started breaking on GCC 4.5 if T contains any bit fields.)

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  • For what purpose does java have a float primitive type?

    - by Roman
    I heard plenty times different claims about float type in java. The most popular issues typicaly regard to converting float value to double and vice versa. I read (rather long time ago and not sure that it's actual now with new JVM) that float gives much worse performance then double. And it's also not recommended to use float in scientific applications which should have certain accuracy. I also remember that when I worked with AWT and Swing I had some problems with using float or double (like using Point2D.Float or Point2D.Double). So, I see only 2 advantages of float over double: it needs only 4 bytes while double needs 8 bytes JMM garantees that assignment operation is atomic with float variables while it's not atomic with double's. Are there any other cases where float is better then double? Do you use float's in your applications? It seems to me that the only valuable reason java has float is backward compatibility.

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  • gem install cannot find a header file

    - by Milktrader
    Following along the github README for talib_ruby: sudo port install ta-lib Complete. Next is where the trouble begins. sudo env ARCHFLAGS="-arch PLATFORM" gem install talib_ruby -- --with-talib-include=ABSOLUTE_PATH_TO_TALIB_HEADERS --with-talib-lib=ABSOLUTE_PATH_TO_TALIB_LIBS This install fails I believe because apparently it cannot find the ta_abstract.h file talib.c:2:25: error: ta_abstract.h: No such file or directory . . . many more errors I have included in my .bash_profile file the following: export ABSOLUTE_PATH_TO_TALIB_HEADERS=/opt/local/var/macports/software/ta-lib/0.4.0_0/opt/local/include/ta-lib export ABSOLUTE_PATH_TO_TALIB_LIBS=/opt/local/var/macports/software/ta-lib/0.4.0_0/opt/local/lib And indeed the ta_abstract.h file is located where I'm saying in the ABSOLUTE_PATH variable assignment. What gives?

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  • Breakdown of this Ruby code?

    - by randombits
    Would anyone be kind enough to dissect the merge! method? Its usage of conditions and variable assignment looks rather terse, and I'm having a difficult time following it. Would love to hear a Ruby-savvy developer break this apart. module ActiveRecord class Errors def merge!(errors, options={}) fields_to_merge = if only=options[:only] only elsif except=options[:except] except = [except] unless except.is_a?(Array) except.map!(&:to_sym) errors.entries.map(&:first).select do |field| !except.include?(field.to_sym) end else errors.entries.map(&:first) end fields_to_merge = [fields_to_merge] unless fields_to_merge.is_a?(Array) fields_to_merge.map!(&:to_sym) errors.entries.each do |field, msg| add field, msg if fields_to_merge.include?(field.to_sym) end end end end

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  • How can i assign a two dimensional array into other temporary two dimensional array.....?? in C Programming..

    - by AGeek
    Hi I am trying to store the contents of two dimensional array into a temporary array.... How is it possible... I don't want looping over here, as it would add an extra overhead.. Any pointer notation would be good. struct bucket { int nStrings; char strings[MAXSTRINGS][MAXWORDLENGTH]; }; void func() { char **tArray; int tLenArray = 0; for(i=0; i<TOTBUCKETS-1; i++) { if(buck[i].nStrings != 0) { tArray = buck[i].strings; tLenArray = buck[i].nStrings; } } } The error here i am getting is:- [others@centos htdocs]$ gcc lexorder.c lexorder.c: In function âlexSortingâ: lexorder.c:40: warning: assignment from incompatible pointer type Please let me know if this needs some more explanaition...

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  • Memory management technique for Objective-C iVars/properties

    - by David Rea
    Is the following code doing anything unnecessary? @interface MyClass { NSArray *myArray; } -(void)replaceArray:(NSArray *)newArray; @implementation MyClass -(void)replaceArray:(NSArray *)newArray { if( myArray ) { [myArray release]; myArray = nil; } myArray = [[NSArray alloc] initWithArray: newArray]; } @end What if I made the following changes: 1) Made myArray a property: @property (nonatomic, retain) NSArray myArray; 2) Changed the assignment to: self.myArray = [NSArray arrayWithArray: newArray]; Would that allow me to remove the conditional?

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  • C++: concatenate ints in an array?

    - by Nate
    As part of a homework assignment I need to concatenate certain values in an array in C++. So, for example if I have: int v[] = {0,1,2,3,4} I may need at some point to concatenate v[1] - v[4] so that I get an int with the value 1234. I got it working using stringstream, by appending the values onto the stringstream and then converting back to an integer. However, throughout the program there will eventually be about 3 million different permutations of v[] passed to my toInt() function, and the stringstream seems rather expensive (at least when dealing with that many values). it's working, but very slow and I'm trying to do whatever I can to optimize it. Is there a more optimal way to concatenate ints in an array in C++? I've done some searching and nearly everywhere seems to just suggest using stringstream (which works, but seems to be slowing my program down a lot). EDIT: Just clarifying, I do need the result to be an int.

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  • Breadth first search all paths

    - by Amndeep7
    First of all, thank you for looking at this question. For a school assignment we're supposed to create a BFS algorithm and use it to do various things. One of these things is that we're supposed to find all of the paths between the root and the goal nodes of a graph. I have no idea how to do this as I can't find a way to keep track of all of the alternate routes without also including copies/cycles. Here is my BFS code: def makePath(predecessors, last): return makePath(predecessors, predecessors[last]) + [last] if last else [] def BFS1b(node, goal): Q = [node] predecessor = {node:None} while Q: current = Q.pop(0) if current[0] == goal: return makePath(predecessor, goal) for subnode in graph[current[0]][2:]: if subnode[0] not in predecessor: predecessor[subnode[0]] = current[0] Q.append(subnode[0]) A conceptual push in the right direction would be greatly appreciated. tl;dr How do I use BFS to find all of the paths between two nodes?

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  • Finding if a path between 2 sides of a game board exists

    - by Meny
    Hi, i'm currently working on a game as an assignment for school in java. the game cuurently is designed for Console. the game is for 2 players, one attacking from north to south, and the other from west to east. the purpose of the game is to build a "bridge"/"path" between the 2 of your sides before your opponent does. for example: A B C D E F 1 _ _ X _ _ _ 1 2 O X X _ _ _ 2 3 O X O O O O 3 4 O X O _ _ _ 4 5 X X _ _ _ _ 5 6 X O _ _ _ _ 6 A B C D E F player that attacks from north to south won (path/bridge from C to A) my problem is, what algorithm would be good to check if the user have managed to create a path (will be checked at the end of each turn). you're help would be very appreciated.

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  • How to write data by dynamic parameter name

    - by Maxim Welikobratov
    I need to be able to write data to datastore of google-app-engine for some known entity. But I don't want write assignment code for each parameter of the entity. I meen, I don't want do like this val_1 = self.request.get('prop_1') val_2 = self.request.get('prop_2') ... val_N = self.request.get('prop_N') item.prop_1 = val_1 item.prop_2 = val_2 ... item.prop_N = val_N item.put() instead, I want to do something like this args = self.request.arguments() for prop_name in args: item.set(prop_name, self.request.get(prop_name)) item.put() dose anybody know how to do this trick?

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  • How does PHP's list function work?

    - by Jacob Relkin
    After recently answering a couple of questions here on SO that involved utilizing PHP's list function, I wondered, "how in the world does that function actually work under the hood?". I was thinking about something like using func_get_args() and then iterating through the argument list, and that's all nice and peachy, but then how in the world does the assignment part work? list(...) = array($x, $y, $z); isn't this ^ evaluated first? So to be precise, my question is how is the list function able to create scoped variables which get assigned to the not-yet evaluated array?

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  • Cannot execute cut-n-paste VBScripts

    - by IcedDante
    I have been going mad trying to figure out why my scripts weren't working, until I started copying and pasting sample source code directly from a few websites only to have it fail there as well. I am getting the following error in my VBScripts: C:\temp\vbs\script.vbs(19, 53) Microsoft VBScript compilation error: Expected statement' For a line of code that looks like this: wdoc.Application.Selection.Find.Execute Replace:=wdReplaceAll This is interfacing with Microsft Word in Office 2007 to conduct a search and replace. Index 53 point directly to the := part of the assignment. Since this type of syntax doesn't work on my machine and I am using it from several websites, I was wondering if the cscript.exe I use is out of date. Am I not calling cscript properly?

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  • Enumeration classes in Java

    - by Crystal
    I have one class that declares an enumeration type as: public enum HOME_LOAN_TERMS {FIFTEEN_YEAR, THIRTY_YEAR}; Is this type usable in another class? I'm basically trying to complete a homework assignment where we have two types of loans, and one loanManager class. When I try to use the HOME_LOAN_TERMS.THIRTY_YEAR in my loanManager class that does not extend or implement the loan class, I get an error saying it 'cannot find symbol HOME_LOAN_TERMS.' So I did not know if my loanManager class needed to implement the two different loan classes. Thanks.

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  • writing to a file in nasm using system calls

    - by yurib
    As part of an assignment I'm supposed to write to a file using system calls. Everything works fine except when I try to open the file in gedit (linux), it says it can't identify the character encoding. Notepad (on windows) opens the file just fine. Why doesn't it work on linux ? here's the code: section .text global _start _start: mov EAX, 8 mov EBX, filename mov ECX, 0700 int 0x80 mov EBX, EAX mov EAX, 4 mov ECX, text mov EDX, textlen int 0x80 mov EAX, 6 int 0x80 mov eax, 1 int 0x80 section .data filename db "./output.txt", 0 text db "hello world", 0 textlen equ $ - text thanks :)

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  • How can I modify my Shunting-Yard Algorithm so it accepts unary operators?

    - by KingNestor
    I've been working on implementing the Shunting-Yard Algorithm in JavaScript for class. Here is my work so far: var userInput = prompt("Enter in a mathematical expression:"); var postFix = InfixToPostfix(userInput); var result = EvaluateExpression(postFix); document.write("Infix: " + userInput + "<br/>"); document.write("Postfix (RPN): " + postFix + "<br/>"); document.write("Result: " + result + "<br/>"); function EvaluateExpression(expression) { var tokens = expression.split(/([0-9]+|[*+-\/()])/); var evalStack = []; while (tokens.length != 0) { var currentToken = tokens.shift(); if (isNumber(currentToken)) { evalStack.push(currentToken); } else if (isOperator(currentToken)) { var operand1 = evalStack.pop(); var operand2 = evalStack.pop(); var result = PerformOperation(parseInt(operand1), parseInt(operand2), currentToken); evalStack.push(result); } } return evalStack.pop(); } function PerformOperation(operand1, operand2, operator) { switch(operator) { case '+': return operand1 + operand2; case '-': return operand1 - operand2; case '*': return operand1 * operand2; case '/': return operand1 / operand2; default: return; } } function InfixToPostfix(expression) { var tokens = expression.split(/([0-9]+|[*+-\/()])/); var outputQueue = []; var operatorStack = []; while (tokens.length != 0) { var currentToken = tokens.shift(); if (isNumber(currentToken)) { outputQueue.push(currentToken); } else if (isOperator(currentToken)) { while ((getAssociativity(currentToken) == 'left' && getPrecedence(currentToken) <= getPrecedence(operatorStack[operatorStack.length-1])) || (getAssociativity(currentToken) == 'right' && getPrecedence(currentToken) < getPrecedence(operatorStack[operatorStack.length-1]))) { outputQueue.push(operatorStack.pop()) } operatorStack.push(currentToken); } else if (currentToken == '(') { operatorStack.push(currentToken); } else if (currentToken == ')') { while (operatorStack[operatorStack.length-1] != '(') { if (operatorStack.length == 0) throw("Parenthesis balancing error! Shame on you!"); outputQueue.push(operatorStack.pop()); } operatorStack.pop(); } } while (operatorStack.length != 0) { if (!operatorStack[operatorStack.length-1].match(/([()])/)) outputQueue.push(operatorStack.pop()); else throw("Parenthesis balancing error! Shame on you!"); } return outputQueue.join(" "); } function isOperator(token) { if (!token.match(/([*+-\/])/)) return false; else return true; } function isNumber(token) { if (!token.match(/([0-9]+)/)) return false; else return true; } function getPrecedence(token) { switch (token) { case '^': return 9; case '*': case '/': case '%': return 8; case '+': case '-': return 6; default: return -1; } } function getAssociativity(token) { switch(token) { case '+': case '-': case '*': case '/': return 'left'; case '^': return 'right'; } } It works fine so far. If I give it: ((5+3) * 8) It will output: Infix: ((5+3) * 8) Postfix (RPN): 5 3 + 8 * Result: 64 However, I'm struggling with implementing the unary operators so I could do something like: ((-5+3) * 8) What would be the best way to implement unary operators (negation, etc)? Also, does anyone have any suggestions for handling floating point numbers as well? One last thing, if anyone sees me doing anything weird in JavaScript let me know. This is my first JavaScript program and I'm not used to it yet.

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  • How can I log into gmail in a script/program using HTTPS?

    - by master chief
    My teacher has given me as an assignment to log into gmail and then send one e-mail or read the list of unread e-mails, but I can't use IMAP/POP3/SMTP or anything that isn't HTTP or HTTPS. I've tried looking for libraries in Ruby/Java to do it but nothing really worked for me. I tried looking at the gmail source code page but I couldn't really understand what was going on. The page seems to call a post method on a link, but sniffing the packets what I saw was a GET apparently using a session generated using the info I send. So sending it "raw" didn't work either. I've no idea what to do now.

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  • Vector of Object Pointers, general help and confusion

    - by Staypuft
    Have a homework assignment in which I'm supposed to create a vector of pointers to objects Later on down the load, I'll be using inheritance/polymorphism to extend the class to include fees for two-day delivery, next day air, etc. However, that is not my concern right now. The final goal of the current program is to just print out every object's content in the vector (name & address) and find it's shipping cost (weight*cost). My Trouble is not with the logic, I'm just confused on few points related to objects/pointers/vectors in general. But first my code. I basically cut out everything that does not mater right now, int main, will have user input, but right now I hard-coded two examples. #include <iostream> #include <string> #include <vector> using namespace std; class Package { public: Package(); //default constructor Package(string d_name, string d_add, string d_zip, string d_city, string d_state, double c, double w); double calculateCost(double, double); void Print(); ~Package(); private: string dest_name; string dest_address; string dest_zip; string dest_city; string dest_state; double weight; double cost; }; Package::Package() { cout<<"Constucting Package Object with default values: "<<endl; string dest_name=""; string dest_address=""; string dest_zip=""; string dest_city=""; string dest_state=""; double weight=0; double cost=0; } Package::Package(string d_name, string d_add, string d_zip, string d_city, string d_state, string r_name, string r_add, string r_zip, string r_city, string r_state, double w, double c){ cout<<"Constucting Package Object with user defined values: "<<endl; string dest_name=d_name; string dest_address=d_add; string dest_zip=d_zip; string dest_city=d_city; string dest_state=d_state; double weight=w; double cost=c; } Package::~Package() { cout<<"Deconstructing Package Object!"<<endl; delete Package; } double Package::calculateCost(double x, double y){ return x+y; } int main(){ double cost=0; vector<Package*> shipment; cout<<"Enter Shipping Cost: "<<endl; cin>>cost; shipment.push_back(new Package("tom r","123 thunder road", "90210", "Red Bank", "NJ", cost, 10.5)); shipment.push_back(new Package ("Harry Potter","10 Madison Avenue", "55555", "New York", "NY", cost, 32.3)); return 0; } So my questions are: I'm told I have to use a vector of Object Pointers, not Objects. Why? My assignment calls for it specifically, but I'm also told it won't work otherwise. Where should I be creating this vector? Should it be part of my Package Class? How do I go about adding objects into it then? Do I need a copy constructor? Why? What's the proper way to deconstruct my vector of object pointers? Any help would be appreciated. I've searched for a lot of related articles on here and I realize that my program will have memory leaks. Using one of the specialized ptrs from boost:: will not be available for me to use. Right now, I'm more concerned with getting the foundation of my program built. That way I can actually get down to the functionality I need to create. Thanks.

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  • Losing data after reading them correct from file

    - by user1388172
    i have the fallowing class of object with a class a data structure which i use in main combined. The ADT(abstract data type) is a linked list. After i read from file the input data and create and object which at print looks just fine after a print. after i push_back() the 3-rd int variable get initializated to 0. So example and code: Example: ex.in: 1 7 31 2 2 2 3 3 3 now i create objects from each line, which at print look as they suppose, but after push_back(): 1 7 0 2 2 0 3 3 0 Class.h: class RAngle { private: int x,y,l,b; public: int solution,prec; RAngle(){ x = y = solution = prec = b = l =0; } RAngle(int i,int j,int k){ x = i; y = j; l = k; solution = 0; prec=0; b=0; } friend ostream& operator << (ostream& out, const RAngle& ra){ out << ra.x << " " << ra.y << " " << ra.l <<endl; return out; } friend istream& operator >>( istream& is, RAngle& ra){ is >> ra.x; is >> ra.y; is >> ra.l; return is ; } }; ADT.h: template <class T> class List { private: struct Elem { T data; Elem* next; }; Elem* first; T pop_front(){ if (first!=NULL) { T aux = first->data; first = first->next; return aux; } T a; return a; } void push_back(T data){ Elem *n = new Elem; n->data = data; n->next = NULL; if (first == NULL) { first = n; return ; } Elem *current; for(current=first;current->next != NULL;current=current->next); current->next = n; } Main.cpp(after i call this function in main which prints object as they suppose to be the x var(from RAngle class) changes to 0 in all cases.) void readData(List <RAngle> &l){ RAngle r; ifstream f_in; f_in.open("ex.in",ios::in); for(int i=0;i<10;++i){ f_in >> r; cout << r; l.push_back(r); }

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  • MVC & Design patterns in C++

    - by theunanonim
    I have an assignment (university level) in C++ The application that was done so far: - MVC agenda - the views are command-line - Agenda contains a list of contacts - a contact may be a friend or an acquiantance - Agenda may contain also a Company that is a contact and may contain other contacts (sorry the code is already too big as I tried to keep the MVC aspect of the application, and I can't post it here or request your time to study it..) To do: - implement factory method pattern - implement observer pattern - implement strategy pattern - implement visitor pattern The evaluation will depend on the number of added patterns and places they have been added. Am I an idiot or this is the stupidies possible assignement ? If not, please help me with some basic tips.. which one where ? Best Regards. P.S. Sorry for my English

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  • How do you assign a JavaScript 'onclick' attribute dynamically?

    - by Jack Roscoe
    Hi, I'm creating a button dynamically using JavaScript and at the same time assigning attributes such as 'ID', 'type' etc and also 'onclick' in order to trigger a function. All works fine apart from the assignment of the 'onclick'. When clicked, the button is not triggering the function as it is supposed to. the function I'm trying to run is 'navigate(-1)' as seen below. Where am I going wrong? Here's my code: function loadNavigation() { var backButton; backButton = document.createElement('input'); backButton.ID = 'backButton'; backButton.type = 'button'; backButton.value='Back'; backButton.onclick = 'navigate(-1)'; document.body.appendChild(backButton); }

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  • Trouble compiling some decompiled C# code

    - by Colin O'Dell
    I was decompiling an open-source project (because the source for the latest version hasn't been released yet). Using RedGate's Reflector tool, it gave me this block of code: if(somecondition == true) { ref Vector3i vectoriRef; float num17 = length - num; Vector3i end = vectori3; (vectoriRef = (Vector3i) &end)[1] = vectoriRef[1] - ((int) num17); } somecondition is a boolean. length and num are floats defined outside the code. vectori3 is also defined outside the code and is of type Vector3i. The type Vector3i is essentially this code, but with x, y, and z stored as integers. When I try to compile this decompiled code, I get the following errors: Line 2: Only assignment, call, increment, decrement, and new object expressions can be used as a statement Line 3: ; expected Line 3: Invalid expression term 'ref' Line 6: 'Vector3i' is a 'type' but is used like a 'variable' Any thoughts on how I can fix this code so it compiles correctly and does whatever it was intended to do?

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  • Default Arguments in Matlab

    - by Scott
    Hello. Is it possible to have default arguments in Matlab? For instance, here: function wave(a,b,n,k,T,f,flag,fTrue=inline('0')) I would like to have the true solution be an optional argument to the wave function. If it is possible, can anyone demonstrate the proper way to do this? Currently, I am trying what I posted above and I get: ??? Error: File: wave.m Line: 1 Column: 37 The expression to the left of the equals sign is not a valid target for an assignment. Thanks!

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  • What could possibly cause this error when declaring an object inside a class?

    - by M4design
    I'm battling with this assignment :) I've got two classes: Ocean and Grid. When I declare an object of the Grid inside the Ocean: unsigned int sharkCount; Grid grid; The compiler/complainer says: error C2146: syntax error : missing ';' before identifier 'grid' Can you possibly predict what produces this error with the limited info I provided? It seems that as if the Ocean doesn't like the Grid class. Could this be because of the poor implementation of the grid class. BTW the Grid has a default constructor. Yet the error happens in compiling time!. EDIT: They're each in separate header file, and I've included the Grid.h in the Ocean.h.

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  • Playground for Artificial Intelligence?

    - by Dolph Mathews
    In school, one of my professors had created a 3D game (not just an engine), where all the players were entirely AI-controlled, and it was our assignment to program the AI of a single player. We were basically provided an API to interact with the game world. Our AI implementations were then dropped into the game together, and we watched as our programs went to battle against each other. It was like robot soccer, but virtual, and with lots of big guns. I'm now looking for anything similar (and open source) to play with. (Preferably in Java, but I'm open to any language.) I'm not looking for a game engine, or a framework... I'm looking for a complete game that simply lacks AI code... preferably set up for this kind of exercise. Suggestions?

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  • basic json > struct question

    - by danwoods
    I'm working with twitter's api, trying to get the json data from http://search.twitter.com/trends/current.json which looks like: {"as_of":1268069036,"trends":{"2010-03-08 17:23:56":[{"name":"Happy Women's Day","query":"\"Happy Women's Day\" OR \"Women's Day\""},{"name":"#MusicMonday","query":"#MusicMonday"},{"name":"#MM","query":"#MM"},{"name":"Oscars","query":"Oscars OR #oscars"},{"name":"#nooffense","query":"#nooffense"},{"name":"Hurt Locker","query":"\"Hurt Locker\""},{"name":"Justin Bieber","query":"\"Justin Bieber\""},{"name":"Cmon","query":"Cmon"},{"name":"My World 2","query":"\"My World 2\""},{"name":"Sandra Bullock","query":"\"Sandra Bullock\""}]}} My structs look like: type trend struct { name string query string } type trends struct { id string arr_of_trends []trend } type Trending struct { as_of string trends_obj trends } and then I parse the JSON into a variable of type Trending. I'm very new to JSON so my main concern is making sure I've have the data structure correctly setup to hold the returned json data. I'm writing this in 'Go' for a project for school. (This is not part of a particular assignment, just something I'm demo-ing for a presentation on the language)

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