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  • Can a function return an object? Objective-C and NSMutableArray

    - by seaworthy
    I have an NSMutableArray. It's members eventually become members of an array instance in a class. I want to put the instantiantion of NSMutable into a function and to return an array object. If I can do this, I can make some of my code easier to read. Is this possible? Here is what I am trying to figure out. //Definition: > function Objects (float a, float b) { > NSMutableArray *array = [[NSMutableArray alloc] init]; > [array addObject:[NSNumber numberWithFloat:a]]; > [array addObject:[NSNumber numberWithFloat:b]]; > //[release array]; ???????? return array; > } //Declaration: Math *operator = [[Math alloc] init]; [operator findSum:Objects(20.0,30.0)]; My code compiles if I instantiate NSMutableArray right before I send the message to the receiver. I know I can have an array argument along with the method. What I have problem seeing is how to use a function and to replace the argument with a function call. Any help is appreciated. I am interested in the concept not in suggestions to replace the findSum method.

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  • Sorting Arrays by More the One Value, and Prioritizing the Sort based on Column data.

    - by Mark Tomlin
    I'm looking for a way to sort an array (we call this a row), with an array of values (that I'll call columns). Each row has columns that must be sorted based on the priority of: timetime, lapcount & timestamp. Each column cotains this information: split1, split2, split3, laptime, lapcount, timestamp. laptime if in hundredths of a second. (1:23.45 or 1 Minute, 23 Seconds & 45 Hundredths is 8345.) Lapcount is a simple unsigned tiny int, or unsigned char. timestamp is unix epoch. The lowest laptime should be at the get a better standing in this sort. Should two peoples laptimes equal, then timestamp will be used to give the better standing in this sort. Should two peoples timestamp equal, then the person with less of a lapcount get's the better standing in this sort. By better standing, I mean closer to the top of the array, closer to the index of zero where it a numerical array. I think the array sorting functions built into php can do this with a callback, I was wondering what the best approch was for a weighted sort like this would be.

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  • Sorting Arrays by More the One Value, and Prioritizing the Sort based on Column data.

    - by Mark Tomlin
    I'm looking for a way to sort an array, based on the information in each row, based on the information in certain cells, that I'll call columns. Each row has columns that must be sorted based on the priority of: timetime, lapcount & timestamp. Each column cotains this information: split1, split2, split3, laptime, lapcount, timestamp. laptime if in hundredths of a second. (1:23.45 or 1 Minute, 23 Seconds & 45 Hundredths is 8345.) Lapcount is a simple unsigned tiny int, or unsigned char. timestamp is unix epoch. The lowest laptime should be at the get a better standing in this sort. Should two peoples laptimes equal, then timestamp will be used to give the better standing in this sort. Should two peoples timestamp equal, then the person with less of a lapcount get's the better standing in this sort. By better standing, I mean closer to the top of the array, closer to the index of zero where it a numerical array. I think the array sorting functions built into php can do this with a callback, I was wondering what the best approch was for a weighted sort like this would be.

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  • Resolving Circular References for Objects Implementing ISerializable

    - by Chris
    I'm writing my own IFormatter implementation and I cannot think of a way to resolve circular references between two types that both implement ISerializable. Here's the usual pattern: [Serializable] class Foo : ISerializable { private Bar m_bar; public Foo(Bar bar) { m_bar = bar; m_bar.Foo = this; } public Bar Bar { get { return m_bar; } } protected Foo(SerializationInfo info, StreamingContext context) { m_bar = (Bar)info.GetValue("1", typeof(Bar)); } public void GetObjectData(SerializationInfo info, StreamingContext context) { info.AddValue("1", m_bar); } } [Serializable] class Bar : ISerializable { private Foo m_foo; public Foo Foo { get { return m_foo; } set { m_foo = value; } } public Bar() { } protected Bar(SerializationInfo info, StreamingContext context) { m_foo = (Foo)info.GetValue("1", typeof(Foo)); } public void GetObjectData(SerializationInfo info, StreamingContext context) { info.AddValue("1", m_foo); } } I then do this: Bar b = new Bar(); Foo f = new Foo(b); bool equal = ReferenceEquals(b, b.Foo.Bar); // true // Serialise and deserialise b equal = ReferenceEquals(b, b.Foo.Bar); If I use an out-of-the-box BinaryFormatter to serialise and deserialise b, the above test for reference-equality returns true as one would expect. But I cannot conceive of a way to achieve this in my custom IFormatter. In a non-ISerializable situation I can simply revisit "pending" object fields using reflection once the target references have been resolved. But for objects implementing ISerializable it is not possible to inject new data using SerializationInfo. Can anyone point me in the right direction?

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  • How to prevent Hibernate from nullifying relationship column during entity removal

    - by Grzegorz
    I have two entities, A and B. I need to easily retrieve entities A, joined with entities B on the condition of equal values of some column (some column from A equal to some column in B). Those columns are not primary or foreign keys, they contain same business data. I just need to have access from each instance of A to the collection of B's with the same value of this column. So I model it like this: class A { @OneToMany @JoinColumn(name="column_in_B", referencedColumnName="column_in_A") Collection<B> bs; This way, I can run queries like "select A join fetch a.bs b where b...." (Actually, the real relationship here is many-to-many. But when I use @ManyToMany, Hibernate forces me to use join table, which doesnt exist here. So I have to use @OneToMany as workaround). So far so good. The main problem is: whenever I delete an instance of A, hibernate calls "Update B set column_in_B = null", becuase it thinks the column_in_B is foreign key pointing at primary key in A (and because row in A is deleted, it tries to clean the foreign key in B). BUT the column_in_B IS NOT a foreign key, and can't be modified, because it causes data lost (and this column is NOT NULL anyway in my case, causing data integerity exception to be thrown). Plese help me with this. How to model such relationships with Hibernate? (I would call it "virtual relationships", or "secondary relationships" or so: as they are not based on foreign keys, they are just some shortcuts which allows for retrieving related objects and quering for them with HQL)

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  • Is it okay to implement reference counting through composition?

    - by Billy ONeal
    Most common re-usable reference counted objects use private inheritance to implement re-use. I'm not a huge fan of private inheritance, and I'm curious if this is an acceptable way of handling things: class ReferenceCounter { std::size_t * referenceCount; public: ReferenceCounter() : referenceCount(NULL) {}; ReferenceCounter(ReferenceCounter& other) : referenceCount(other.referenceCount) { if (!referenceCount) { referenceCount = new std::size_t(1); other.referenceCount = referenceCount; } else { ++(*referenceCount); } }; ReferenceCounter& operator=(const ReferenceCounter& other) { ReferenceCounter temp(other); swap(temp); return *this; }; void swap(ReferenceCounter& other) { std::swap(referenceCount, other.referenceCount); }; ~ReferenceCounter() { if (referenceCount) { --(*referenceCount); if (!*referenceCount) delete referenceCount; } }; operator bool() const { return referenceCount && (*referenceCount != 0); }; }; class SomeClientClass { HANDLE someHandleThingy; ReferenceCounter objectsStillActive; public: SomeClientClass() { //Construct handle thingy } ~SomeClientClass() { if (objectsStillActive) return; //Release resources }; }; or are there subtle problems with this I'm not seeing?

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  • Changing associativity

    - by Sorush Rabiee
    Hi... The associativity of stream insertion operator is rtl, forgetting this fact sometimes cause to runtime or logical errors. for example: 1st- int F() { static int internal_counter c=0; return ++c; } in the main function: //....here is main() cout<<”1st=”<<F()<<”,2nd=”<<F()<<”,3rd=”<<F(); and the output is: 1st=3,2nd=2,3rd=1 that is different from what we expect at first look. 2nd- suppose that we have an implementation of stack data structure like this: // //... a Stack<DataType> class …… // Stack<int> st(10); for(int i=1;i<11;i++) st.push(i); cout<<st.pop()<<endl<<st.pop()<<endl<<st.pop()<<endl<<st.pop()<<endl; expected output is something like: 10 9 8 7 but we have: 7 8 9 10 There is no internal bug of << implementation but it can be so confusing... and finally[:-)] my question: is there any way to change assocativity of an operator by overloading it?

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  • Examples of monoids/semigroups in programming

    - by jkff
    It is well-known that monoids are stunningly ubiquitous in programing. They are so ubiquitous and so useful that I, as a 'hobby project', am working on a system that is completely based on their properties (distributed data aggregation). To make the system useful I need useful monoids :) I already know of these: Numeric or matrix sum Numeric or matrix product Minimum or maximum under a total order with a top or bottom element (more generally, join or meet in a bounded lattice, or even more generally, product or coproduct in a category) Set union Map union where conflicting values are joined using a monoid Intersection of subsets of a finite set (or just set intersection if we speak about semigroups) Intersection of maps with a bounded key domain (same here) Merge of sorted sequences, perhaps with joining key-equal values in a different monoid/semigroup Bounded merge of sorted lists (same as above, but we take the top N of the result) Cartesian product of two monoids or semigroups List concatenation Endomorphism composition. Now, let us define a quasi-property of an operation as a property that holds up to an equivalence relation. For example, list concatenation is quasi-commutative if we consider lists of equal length or with identical contents up to permutation to be equivalent. Here are some quasi-monoids and quasi-commutative monoids and semigroups: Any (a+b = a or b, if we consider all elements of the carrier set to be equivalent) Any satisfying predicate (a+b = the one of a and b that is non-null and satisfies some predicate P, if none does then null; if we consider all elements satisfying P equivalent) Bounded mixture of random samples (xs+ys = a random sample of size N from the concatenation of xs and ys; if we consider any two samples with the same distribution as the whole dataset to be equivalent) Bounded mixture of weighted random samples Which others do exist?

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  • restrict documents for mapreduce with mongoid

    - by theBernd
    I implemented the pearson product correlation via map / reduce / finalize. The missing part is to restrict the documents (representing users) to be processed via a filter query. For a simple query like mapreduce(mapper, reducer, :finalize => finalizer, :query => { :name => 'Bernd' }) I get this to work. But my filter criteria is a little bit more complicated: I have one set of preferences which need to have at least one common element and another set of preferences which may not have a common element. In a later step I also want to restrict this to documents (users) within a certain geographical distance. Currently I have this code working in my map function, but I would prefer to separate this into either query params as supported by mongoid or a javascript function. All my attempts to solve this failed since the code is either ignored or raises an error. I did a couple of tests. A regular find like User.where(:name.in => ['Arno', 'Bernd', 'Claudia']) works and returns #<Mongoid::Criteria:0x00000101f0ea40 @selector={:name=>{"$in"=>["Arno", "Bernd", "Claudia"]}}, @options={}, @klass=User, @documents=[]> Trying the same with mapreduce User.collection. mapreduce(mapper, reducer, :finalize => finalizer, :query => { :name.in => ['Arno', 'Bernd', 'Claudia'] }) fails with `serialize': keys must be strings or symbols (TypeError) in bson-1.1.5 The intermediate query parameter looks like this :query=>{#<Mongoid::Criterion::Complex:0x00000101a209e8 @key=:name, @operator="in">=>["Arno", "Bernd", "Claudia"]} and at least @operator looks a bit weird to me. I'm also uncertain if the class name can be omitted. BTW - I'm using mongodb 1.6.5-x86_64, and the mongoid 2.0.0.beta.20, mongo 1.1.5 and bson 1.1.5 gems on MacOS. What am I doing wrong? Thanks in advance.

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  • How do I write test code to exercise a C# generic Pair<TKey, TValue> ?

    - by Scott Davies
    Hi, I am reading through Jon Skeet's "C# in Depth", first edition (which is a great book). I'm in section 3.3.3, page 84, "Implementing Generics". Generics always confuse me, so I wrote some code to exercise the sample. The code provided is: using System; using System.Collections.Generic; public sealed class Pair<TFirst, TSecond> : IEquatable<Pair<TFirst, TSecond>> { private readonly TFirst first; private readonly TSecond second; public Pair(TFirst first, TSecond second) { this.first = first; this.second = second; } ...property getters... public bool Equals(Pair<TFirst, TSecond> other) { if (other == null) { return false; } return EqualityComparer<TFirst>.Default.Equals(this.First, other.First) && EqualityComparer<TSecond>.Default.Equals(this.Second, other.Second); } My code is: class MyClass { public static void Main (string[] args) { // Create new pair. Pair thePair = new Pair(new String("1"), new String("1")); // Compare a new pair to previous pair by generating a second pair. if (thePair.Equals(new Pair(new string("1"), new string("1")))) System.Console.WriteLine("Equal"); else System.Console.WriteLine("Not equal"); } } The compiler complains: "Using the generic type 'ManningListing36.Paie' requires 2 type argument(s) CS0305" What am I doing wrong ? Thanks, Scott

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  • C++ error: expected initializer before ‘&’ token

    - by Werner
    Hi, the following piece of C++ code compiled two years ago in a suse 10.1 Linux machine. #ifndef DATA_H #define DATA_H #include <iostream> #include <iomanip> inline double sqr(double x) { return x*x; } enum Direction { X,Y,Z }; inline Direction next(const Direction d) { switch(d) { case X: return Y; case Y: return Z; case Z: return X; } } inline ostream& operator<<(ostream& os,const Direction d) { switch(d) { case X: return os << "X"; case Y: return os << "Y"; case Z: return os << "Z"; } } ... ... Now, I am trying to compile it on Ubuntu 9.10 and I get the error: data.h:20: error: expected initializer before ‘&’ token which is referred to the line of: inline ostream& operator<<(ostream& os,const Direction d) the g++ used on this machine is: Using built-in specs. Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.4.1-4ubuntu9' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --program-suffix=-4.4 --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --disable-werror --with-arch-32=i486 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu Thread model: posix gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu9) Could you give me some hint about this error? Thanks

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  • Internal "Tee" setup

    - by RadlyEel
    I have inherited some really old VC6.0 code that I am upgrading to VS2008 for building a 64-bit app. One required feature that was implemented long, long ago is overriding std::cout so its output goes simultaneously to a console window and to a file. The implementation depended on the then-current VC98 library implementation of ostream and, of course, is now irretrievably broken with VS2008. It would be reasonable to accumulate all the output until program termination time and then dump it to a file. I got part of the way home by using freopen(), setvbuf(), and ios::sync_with_stdio(), but to my dismay, the internal library does not treat its buffer as a ring buffer; instead when it flushes to the output device it restarts at the beginning, so every flush wipes out all my accumulated output. Converting to a more standard logging function is not desirable, as there are over 1600 usages of "std::cout << " scattered throughout almost 60 files. I have considered overriding ostream's operator<< function, but I'm not sure if that will cover me, since there are global operator<< functions that can't be overridden. (Or can they?) Any ideas on how to accomplish this?

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  • linux new/delete, malloc/free large memory blocks

    - by brian_mk
    Hi folks, We have a linux system (kubuntu 7.10) that runs a number of CORBA Server processes. The server software uses glibc libraries for memory allocation. The linux PC has 4G physical memory. Swap is disabled for speed reasons. Upon receiving a request to process data, one of the server processes allocates a large data buffer (using the standard C++ operator 'new'). The buffer size varies depening upon a number of parameters but is typically around 1.2G Bytes. It can be up to about 1.9G Bytes. When the request has completed, the buffer is released using 'delete'. This works fine for several consecutive requests that allocate buffers of the same size or if the request allocates a smaller size than the previous. The memory appears to be free'd ok - otherwise buffer allocation attempts would eventually fail after just a couple of requests. In any case, we can see the buffer memory being allocated and freed for each request using tools such as KSysGuard etc. The problem arises when a request requires a buffer larger than the previous. In this case, operator 'new' throws an exception. It's as if the memory that has been free'd from the first allocation cannot be re-allocated even though there is sufficient free physical memory available. If I kill and restart the server process after the first operation, then the second request for a larger buffer size succeeds. i.e. killing the process appears to fully release the freed memory back to the system. Can anyone offer an explanation as to what might be going on here? Could it be some kind of fragmentation or mapping table size issue? I am thinking of replacing new/delete with malloc/free and use mallopt to tune the way the memory is being released to the system. BTW - I'm not sure if it's relevant to our problem, but the server uses Pthreads that get created and destroyed on each processing request. Cheers, Brian.

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  • Jqgrid search option hides the grid table

    - by Felix Guerrero
    The issue is when I click on search option (on pager) it shows the search window but the grid gets hide. I'm including the jqmodal.js file. But what I'm ignoring on the code below? css files: jqModal.css jquery-ui-1.8.custom.css ui.jqgrid.css ui.multiselect.css jquery.searchFilter.css js files: jquery.min.js grid.base.js grid.common.js grid.formedit.js grid.setcolumns.js ui.multiselect.js jquery.searchFilter.js jqModal.js The Javascript: $("#list").jqGrid({ url: 'foo_report.php?g=' + $('#fooselect').val() + '&report=1&searchString=null&searchField=null&searchOper=null', datatype: 'json', mtype: 'GET', colNames: ['foo1','foo2', 'foo3'], colModel: [ { name:'rows.foobar1', index: 'foobar1', search:true, jsonmap: 'foobar1', width: 150, align: 'left', sortable:true}, { name:'rows.foobar2', index: 'foobar2', jsonmap: 'foobar2', width: 150, align: 'left'}, { name:'rows.foobar3', index: 'foobar3', jsonmap: 'foobar3', width: 240, align: 'left', sortable: true}], pager: '#pager', rowNum: 8, autowidth: true, rowList: [8, 16], sortname: 'foobar1', sortorder: 'asc', viewrecords: true, search : { caption: "Search...", Find: "Find", Reset: "Reset", odata : ['equal', 'not equal', 'less'], groupOps: [ { op: "AND", text: "all" }, { op: "OR", text: "any" }], matchText: " match", rulesText: " rules" }, caption: 'Foobar Data', jsonReader : { root: "rows", repeatitems: false }, height: 350, width: 800 }); html: <table id="list"></table> <div id="pager"></div>

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  • Weird bug with C++ lambda expressions in VS2010

    - by Andrei Tita
    In a couple of my projects, the following code: class SmallClass { public: int x1, y1; void TestFunc() { auto BadLambda = [&]() { int g = x1 + 1; //ok int h = y1 + 1; //c2296 int l = static_cast<int>(y1); //c2440 }; int y1_copy = y1; //it works if you create a local copy auto GoodLambda = [&]() { int h = y1_copy + 1; //ok int l = this->y1 + 1; //ok }; } }; generates error C2296: '+' : illegal, left operand has type 'double (__cdecl *)(double)' or alternatively error C2440: 'static_cast' : cannot convert from 'double (__cdecl *)(double)' to 'int' You get the picture. It also happens if catching by value. The error seems to be tied to the member name "y1". It happened in different classes, different projects and with (seemingly) any type for y1; for example, this code: [...] MyClass y1; void TestFunc() { auto BadLambda = [&]()->void { int l = static_cast<int>(y1); //c2440 }; } generates both these errors: error C2440: 'static_cast' : cannot convert from 'MyClass' to 'int' No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called error C2440: 'static_cast' : cannot convert from 'double (__cdecl *)(double)' to 'int' There is no context in which this conversion is possible It didn't, however, happen in a completely new project. I thought maybe it was related to Lua (the projects where I managed to reproduce this bug both used Lua), but I did not manage to reproduce it in a new project linking Lua. It doesn't seem to be a known bug, and I'm at a loss. Any ideas as to why this happens? (I don't need a workaround; there are a few in the code already). Using Visual Studio 2010 Express version 10.0.40219.1 Sp1Rel.

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  • How much effort do you have to put in to get gains from using SSE?

    - by John
    Case One Say you have a little class: class Point3D { private: float x,y,z; public: operator+=() ...etc }; Point3D &Point3D::operator+=(Point3D &other) { this->x += other.x; this->y += other.y; this->z += other.z; } A naive use of SSE would simply replace these function bodies with using a few intrinsics. But would we expect this to make much difference? MMX used to involve costly state cahnges IIRC, does SSE or are they just like other instructions? And even if there's no direct "use SSE" overhead, would moving the values into SSE registers and back out again really make it any faster? Case Two Instead, you're working with a less OO-based code base. Rather than an array/vector of Point3D objects, you simply have a big array of floats: float coordinateData[NUM_POINTS*3]; void add(int i,int j) //yes it's unsafe, no overlap check... example only { for (int x=0;x<3;++x) { coordinateData[i*3+x] += coordinateData[j*3+x]; } } What about use of SSE here? Any better? In conclusion Is trying to optimise single vector operations using SSE actually worthwhile, or is it really only valuable when doing bulk operations?

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  • Refactoring exercise with generics

    - by Berryl
    I have a variation on a Quantity (Fowler) class that is designed to facilitate conversion between units. The type is declared as: public class QuantityConvertibleUnits<TFactory> where TFactory : ConvertableUnitFactory, new() { ... } In order to do math operations between dissimilar units, I convert the right hand side of the operation to the equivalent Quantity of whatever unit the left hand side is in, and do the math on the amount (which is a double) before creating a new Quantity. Inside the generic Quantity class, I have the following: protected static TQuantity _Add<TQuantity>(TQuantity lhs, TQuantity rhs) where TQuantity : QuantityConvertibleUnits<TFactory>, new() { var toUnit = lhs.ConvertableUnit; var equivalentRhs = _Convert<TQuantity>(rhs.Quantity, toUnit); var newAmount = lhs.Quantity.Amount + equivalentRhs.Quantity.Amount; return _Convert<TQuantity>(new Quantity(newAmount, toUnit.Unit), toUnit); } protected static TQuantity _Subtract<TQuantity>(TQuantity lhs, TQuantity rhs) where TQuantity : QuantityConvertibleUnits<TFactory>, new() { var toUnit = lhs.ConvertableUnit; var equivalentRhs = _Convert<TQuantity>(rhs.Quantity, toUnit); var newAmount = lhs.Quantity.Amount - equivalentRhs.Quantity.Amount; return _Convert<TQuantity>(new Quantity(newAmount, toUnit.Unit), toUnit); } ... same for multiply and also divide I need to get the typing right for a concrete Quantity, so an example of an add op looks like: public static ImperialLengthQuantity operator +(ImperialLengthQuantity lhs, ImperialLengthQuantity rhs) { return _Add(lhs, rhs); } The question is those verbose methods in the Quantity class. The only change between the code is the math operator (+, -, *, etc.) so it seems that there should be a way to refactor them into a common method, but I am just not seeing it. How can I refactor that code? Cheers, Berryl

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  • templete class c++

    - by inna karpasas
    hi! i try to design a templete for my universty project. i wrote the follwing cod: #ifndef _LinkedList_H_ #define _LinkedList_H_ #include "Link.h" #include <ostream> template <class L>//error one class LinkedList { private: Link<L> *pm_head; Link<L> * pm_tail; int m_numOfElements; Link<L>* FindLink(L * dataToFind); public: LinkedList(); ~LinkedList(); int GetNumOfElements(){return m_numOfElements;} bool Add( L * data); L *FindData(L * data); template <class L> friend ostream & operator<<(ostream& os,const LinkedList<L> listToprint);//error two L* GetDataOnTop(); bool RemoveFromHead(); L* Remove(L * toRemove); this templete uses the link class templete #ifndef _Link_H_ #define _Link_H_ template <class T>//error 3 class Link { private: T* m_data; Link* m_next; Link* m_prev; public: Link(T* data); ~Link(void); bool Link::operator ==(const Link& other)const; /*getters*/ Link* GetNext()const {return m_next;} Link* GetPrev()const {return m_prev;} T* GetData()const {return m_data;} //setters void SetNext(Link* next) {m_next = next;} void SetPrev(Link* prev) {m_prev = prev;} void SetData(T* data) {m_data = data;} }; error one: shadows template parm class L' error two:declaration ofclass L' error three: shadows template parm `class T' i dont understand what is the problem. i can relly usr your help thank you :)

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  • Why do bind1st and bind2nd require constant function objects?

    - by rlbond
    So, I was writing a C++ program which would allow me to take control of the entire world. I was all done writing the final translation unit, but I got an error: error C3848: expression having type 'const `anonymous-namespace'::ElementAccumulator<T,BinaryFunction>' would lose some const-volatile qualifiers in order to call 'void `anonymous-namespace'::ElementAccumulator<T,BinaryFunction>::operator ()(const point::Point &,const int &)' with [ T=SideCounter, BinaryFunction=std::plus<int> ] c:\program files (x86)\microsoft visual studio 9.0\vc\include\functional(324) : while compiling class template member function 'void std::binder2nd<_Fn2>::operator ()(point::Point &) const' with [ _Fn2=`anonymous-namespace'::ElementAccumulator<SideCounter,std::plus<int>> ] c:\users\****\documents\visual studio 2008\projects\TAKE_OVER_THE_WORLD\grid_divider.cpp(361) : see reference to class template instantiation 'std::binder2nd<_Fn2>' being compiled with [ _Fn2=`anonymous-namespace'::ElementAccumulator<SideCounter,std::plus<int>> ] I looked in the specifications of binder2nd and there it was: it took a const AdaptibleBinaryFunction. So, not a big deal, I thought. I just used boost::bind instead, right? Wrong! Now my take-over-the-world program takes too long to compile (bind is used inside a template which is instantiated quite a lot)! At this rate, my nemesis is going to take over the world first! I can't let that happen -- he uses Java! So can someone tell me why this design decision was made? It seems like an odd decision. I guess I'll have to make some of the elements of my class mutable for now...

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  • Error using to_char // to_timestamp

    - by pepersview
    Hello, I have a database in PostgreSQL and I'm developing an application in PHP using this database. The problem is that when I execute the following query I get a nice result in phpPgAdmin but in my PHP application I get an error. The query: SELECT t.t_name, t.t_firstname FROM teachers AS t WHERE t.id_teacher IN (SELECT id_teacher FROM teacher_course AS tcourse JOIN course_timetable AS coursetime ON tcourse.course = coursetime.course AND to_char(to_timestamp('2010-4-12', 'YYYY-MM-DD'),'FMD') = (coursetime.day +1)) AND t.id_teacher NOT IN (SELECT id_teacher FROM teachers_fill WHERE date = '2010-4-12') ORDER BY t.t_name ASC And this is the error in PHP operator does not exist: text = integer (to_timestamp('', 'YYYY-MM-DD'),'FMD') = (courset... ^ HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts. The purpose to solve this error is to use the ORIGINAL query in php with : $date = "2010"."-".$selected_month."-".$selected_day; SELECT t.t_name, t.t_firstname FROM teachers AS t WHERE t.id_teacher IN (SELECT id_teacher FROM teacher_course AS tcourse JOIN course_timetable AS coursetime ON tcourse.course = coursetime.course AND to_char(to_timestamp('$date', 'YYYY-MM-DD'),'FMD') = (coursetime.day +1)) AND t.id_teacher NOT IN (SELECT id_teacher FROM teachers_fill WHERE date = '$date') ORDER BY t.t_name ASC

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  • Execute process conditionally in Windows PowerShell (e.g. the && and || operators in Bash)

    - by Dustin
    I'm wondering if anybody knows of a way to conditionally execute a program depending on the exit success/failure of the previous program. Is there any way for me to execute a program2 immediately after program1 if program1 exits successfully without testing the LASTEXITCODE variable? I tried the -band and -and operators to no avail, though I had a feeling they wouldn't work anyway, and the best substitute is a combination of a semicolon and an if statement. I mean, when it comes to building a package somewhat automatically from source on Linux, the && operator can't be beaten: # Configure a package, compile it and install it ./configure && make && sudo make install PowerShell would require me to do the following, assuming I could actually use the same build system in PowerShell: # Configure a package, compile it and install it .\configure ; if ($LASTEXITCODE -eq 0) { make ; if ($LASTEXITCODE -eq 0) { sudo make install } } Sure, I could use multiple lines, save it in a file and execute the script, but the idea is for it to be concise (save keystrokes). Perhaps it's just a difference between PowerShell and Bash (and even the built-in Windows command prompt which supports the && operator) I'll need to adjust to, but if there's a cleaner way to do it, I'd love to know.

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  • Delphi - Help calling threaded dll function from another thread

    - by cloudstrif3
    I'm using Delphi 2006 and have a bit of a problem with an application I'm developing. I have a form that creates a thread which calls a function that performs a lengthy operation, lets call it LengthyProcess. Inside the LengthyProcess function we also call several Dll functions which also create threads of their own. The problem that I am having is that if I don't use the Synchronize function of my thread to call LengthyProcess the thread stops responding (the main thread is still responding fine). I don't want to use Synchronize because that means the main thread is waiting for LengthyProcess to finish and therefore defeats the purpose of creating a separate thread. I have tracked the problem down to a function inside the dll that creates a thread and then calls WaitFor, this is all done using TThread by the way. WaitFor checks to see if the CurrentThreadID is equal to the MainThreadID and if it is then it will call CheckSychronization, and all is fine. So if we use Synchronize then the CurrentThreadID will equal the MainThreadID however if we do not use Synchronize then of course CurrentThreadID < MainThreadID, and when this happens WaitFor tells the current thread (the thread I created) to wait for the thread created by the DLL and so CheckSynchronization never gets called and my thread ends up waiting forever for the thread created in the dll. I hope this makes sense, sorry I don't know any better way to explain it. Has anyone else had this issue and knows how to solve it please?

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  • SQL: Order randomly when inserting objects to a table

    - by Ekaterina
    I have an UDF that selects top 6 objects from a table (with a union - code below) and inserts it into another table. (btw SQL 2005) So I paste the UDF below and what the code does is: selects objects for a specific city and add a level to those (from table Europe) union that selection with a selection from the same table for objects that are from the same country and add a level to those From the union, selection is made to get top 6 objects, order by level, so the objects from the same city will be first, and if there aren't any available, then objects from the same country will be returned from the selection. And my problem is, that I want to make a random selection to get random objects from table Europe, but because I insert the result of my selection into a table, I can't use order by newid() or rand() function because they are time-dependent, so I get the following errors: Invalid use of side-effecting or time-dependent operator in 'newid' within a function. Invalid use of side-effecting or time-dependent operator in 'rand' within a function. UDF: ALTER FUNCTION [dbo].[Objects] (@id uniqueidentifier) RETURNS @objects TABLE ( ObjectId uniqueidentifier NOT NULL, InternalId uniqueidentifier NOT NULL ) AS BEGIN declare @city varchar(50) declare @country int select @city = city, @country = country from Europe where internalId = @id insert @objects select @id, internalId from ( select distinct top 6 [level], internalId from ( select top 6 1 as [level], internalId from Europe N4 where N4.city = @city and N4.internalId != @id union select top 6 2 as [level], internalId from Europe N5 where N5.countryId = @country and N5.internalId != @id ) as selection_1 order by [level] ) as selection_2 return END If you have fresh ideas, please share them with me. (Just please, don't suggest to order by newid() or to add a column rand() with seed DateTime (by ms or sthg), because that won't work.)

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  • Converting an AnsiString to a Unicode String

    - by jrodenhi
    I'm converting a D2006 program to D2010. I have a value stored in a single byte per character string in my database and I need to load it into a control that has a LoadFromStream, so my plan was to write the string to a stream and use that with LoadFromStream. But it did not work. In studying the problem, I see an issue that tells me that I don't really understand how conversion from AnsiString to Unicode string works. Here is some code I am puzzling over: oStringStream := TStringStream.Create(sBuffer); sUnicodeStream := oPayGrid.sStream; //explicit conversion to unicode string iSize1 := StringElementSize(oPaygrid.sStream); iSize2 := StringElementSize(sUnicodeStream); oStringStream.WriteString(sUnicodeStream); When I get to the last line, iSize1 does equal 1 and iSize2 does equal 2, so that part is what I understood from my reading. But, on the last line, after I write the string to the stream, and look at the Bytes Property of the string, it shows this (the string starts as '16,159'): (49 {$31}, 54 {$36}, 44 {$2C}, 49 {$31}, 53 {$35}, 57 {$39} ... I was expecting that it might look something like (49 {$31}, 00 {$00}, 54 {$36}, 00 {$00}, 44 {$2C}, 00 {$00}, 49 {$31}, 00 {$00}, 53 {$35}, 00 {$00}, 57 {$39}, 00 {$00} ... I'm not getting the right results out of the LoadFromStream because it is reading from the stream two bytes at a time, but the data it is receiving is not arranged that way. What is it that I should do to give the LoadFromStream a well formed stream of data based on a unicode string? Thank you for your help.

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  • Generic InBetween Function.

    - by Luiscencio
    I am tired of writing x > min && x < max so i wawnt to write a simple function but I am not sure if I am doing it right... actually I am not cuz I get an error: bool inBetween<T>(T x, T min, T max) where T:IComparable { return (x > min && x < max); } errors: Operator '>' cannot be applied to operands of type 'T' and 'T' Operator '<' cannot be applied to operands of type 'T' and 'T' may I have a bad understanding of the where part in the function declaring note: for those who are going to tell me that I will be writing more code than before... think on readability =) any help will be appreciated EDIT deleted cuz it was resolved =) ANOTHER EDIT so after some headache I came out with this (ummm) thing following @Jay Idea of extreme readability: public static class test { public static comparision Between<T>(this T a,T b) where T : IComparable { var ttt = new comparision(); ttt.init(a); ttt.result = a.CompareTo(b) > 0; return ttt; } public static bool And<T>(this comparision state, T c) where T : IComparable { return state.a.CompareTo(c) < 0 && state.result; } public class comparision { public IComparable a; public bool result; public void init<T>(T ia) where T : IComparable { a = ia; } } } now you can compare anything with extreme readability =) what do you think.. I am no performance guru so any tweaks are welcome

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