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• Overriding rubies spaceship operator <=>

  - by ericsteen1

  I am trying to override rubies <= (spaceship) operator to sort apples and oranges so that apples come first sorted by weight, and oranges second, sorted by sweetness. Like so: module Fruity attr_accessor :weight, :sweetness def <=>(other) # use Array#<=> to compare the attributes [self.weight, self.sweetness] <=> [other.weight, other.sweetness] end include Comparable end class Apple include Fruity def initialize(w) self.weight = w end end class Orange include Fruity def initialize(s) self.sweetness = s end end fruits = [Apple.new(2),Orange.new(4),Apple.new(6),Orange.new(9),Apple.new(1),Orange.new(22)] p fruits #should work? p fruits.sort But this does not work, can someone tell what I am doing wrong here, or a better way to do this?

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• USing Min/Max with conditional operator

  - by user638501

  Hello All, I am trying to run a query to find max and min values, and then use a conditional operator. however when I try to run the following query, it gives me error - "misuse of aggregate: min()". My query is: SELECT a.prim_id, min(b.new_len*36) as min_new_len, max(b.new_len*36) as max_new_len FROM tb_first a, tb_second b WHERE a.sec_id = b.sec_id AND min_new_len > 1900 AND max_new_len < 75000 GROUP BY a.prim_id ORDER BY avg(b.new_len*36); Any suggestions ?

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• Boolean Not operator in VBScript

  - by Lumi

  Consider the following two conditionals (involving bitwise comparisons) in VBScript: If 1 And 3 Then WScript.Echo "yes" Else WScript.Echo "no" If Not(1 And 3) Then WScript.Echo "yes" Else WScript.Echo "no" Prints first yes, then no, right? cscript not.vbs Wrong! It prints yes twice! Wait a second, the Not operator is supposed to perform logical negation on an expression. The logical negation of true is false, as far as I know. Must I conclude that it doesn't live up to that promise? How and why and what is going on here? What is the rationale, if any?

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• ms-access: missing operator in query expression

  - by every_answer_gets_a_point

  i have this sql statement in access: SELECT * FROM (SELECT [Occurrence Number], [1 0 Preanalytical (Before Testing)], NULL, NULL,NULL FROM [Lab Occurrence Form] WHERE NOT ([1 0 Preanalytical (Before Testing)] IS NULL) UNION SELECT [Occurrence Number], NULL, [2 0 Analytical (Testing Phase)], NULL,NULL FROM [Lab Occurrence Form] WHERE NOT ([2 0 Analytical (Testing Phase)] IS NULL) UNION SELECT [Occurrence Number], NULL, NULL, [3 0 Postanalytical ( After Testing)],NULL FROM [Lab Occurrence Form] WHERE NOT ([3 0 Postanalytical ( After Testing)] IS NULL) UNION SELECT [Occurrence Number], NULL, NULL,NULL [4 0 Other] FROM [Lab Occurrence Form] WHERE NOT ([4 0 Other] IS NULL) ) AS mySubQuery ORDER BY mySubQuery.[Occurrence Number]; everything was fine until i added the last line: SELECT [Occurrence Number], NULL, NULL,NULL [4 0 Other] FROM [Lab Occurrence Form] WHERE NOT ([4 0 Other] IS NULL) i get this error: syntax error (missing operator) in query expression 'NULL [4 0 Other]' anyone have any clues why i am getting this error?

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• Why does std::map operator[] create an object if the key doesn't exist?

  - by n1ck

  Hi, I'm pretty sure I already saw this question somewhere (comp.lang.c++? Google doesn't seem to find it there either) but a quick search here doesn't seem to find it so here it is: Why does the std::map operator[] create an object if the key doesn't exist? I don't know but for me this seems counter-intuitive if you compare to most other operator[] (like std::vector) where if you use it you must be sure that the index exists. I'm wondering what's the rationale for implementing this behavior in std::map. Like I said wouldn't it be more intuitive to act more like an index in a vector and crash (well undefined behavior I guess) when accessed with an invalid key? Refining my question after seeing the answers: Ok so far I got a lot of answers saying basically it's cheap so why not or things similar. I totally agree with that but why not use a dedicated function for that (I think one of the comment said that in java there is no operator[] and the function is called put)? My point is why doesn't map operator[] work like a vector? If I use operator[] on an out of range index on a vector I wouldn't like it to insert an element even if it was cheap because that probably mean an error in my code. My point is why isn't it the same thing with map. I mean, for me, using operator[] on a map would mean: i know this key already exist (for whatever reason, i just inserted it, I have redundancy somewhere, whatever). I think it would be more intuitive that way. That said what are the advantage of doing the current behavior with operator[] (and only for that, I agree that a function with the current behavior should be there, just not operator[])? Maybe it give clearer code that way? I don't know. Another answer was that it already existed that way so why not keep it but then, probably when they (the ones before stl) choose to implement it that way they found it provided an advantage or something? So my question is basically: why choose to implement it that way, meaning a somewhat lack of consistency with other operator[]. What benefit do it give? Thanks

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• Analyzing Python Code: Modulus Operator

  - by Bhubhu Hbuhdbus

  I was looking at some code in Python (I know nothing about Python) and I came across this portion: def do_req(body): global host, req data = "" s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((host, 80)) s.sendall(req % (len(body), body)) tmpdata = s.recv(8192) while len(tmpdata) > 0: data += tmpdata tmpdata = s.recv(8192) s.close() return data This is then called later on with body of huge size, as in over 500,000 bytes. This is sent to an Apache server that has the max request size on the default 8190 bytes. My question is what is happening at the "s.sendall()" part? Obviously the entire body cannot be sent at once and I'm guessing it is reduced by way of the modulus operator. I don't know how it works in Python, though. Can anyone explain? Thanks.

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• Overriding Ruby's spaceship operator <=>

  - by ericsteen1

  I am trying to override Ruby's <= (spaceship) operator to sort apples and oranges so that apples come first sorted by weight, and oranges second, sorted by sweetness. Like so: module Fruity attr_accessor :weight, :sweetness def <=>(other) # use Array#<=> to compare the attributes [self.weight, self.sweetness] <=> [other.weight, other.sweetness] end include Comparable end class Apple include Fruity def initialize(w) self.weight = w end end class Orange include Fruity def initialize(s) self.sweetness = s end end fruits = [Apple.new(2),Orange.new(4),Apple.new(6),Orange.new(9),Apple.new(1),Orange.new(22)] p fruits #should work? p fruits.sort But this does not work, can someone tell what I am doing wrong here, or a better way to do this?

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• C++ vector<T>::iterator operator +

  - by Tom

  Hi, Im holding an iterator that points to an element of a vector, and I would like to compare it to the next element of the vector. Here is what I have Class Point{ public: float x,y; } //Somewhere in my code I do this vector<Point> points = line.getPoints(); foo (points.begin(),points.end()); where foo is: void foo (Vector<Point>::iterator begin,Vector<Point>::iterator end) { std::Vector<Point>::iterator current = begin; for(;current!=end-1;++current) { std::Vector<Point>::iterator next = current + 1; //Compare between current and next. } } I thought that this would work, but current + 1 is not giving me the next element of the vector. I though operator+ was the way to go, but doesnt seem so. Is there a workaround on this? THanks

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• C# == operator in Immediate window behaves differently than at run-time

  - by Damiano

  Try the following in the Immediate window: object a1 = "a"; object a2 = "a"; a1==a2 // outputs false and you'll see that a1 == a2 outputs false. However, at runtime in either a window app or console, you'll get true: object t1 = "a"; object t2 = "a"; MessageBox.Show((t1 == t2).ToString()); // outputs true The runtime behavior is consistent with the definition for the == operator and strings. Does anybody know if this a bug in the Immediate window?

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• Logical xor operator in c++?

  - by RAC

  Is there such a thing? First time I encountered a practical need for it, but I don't see one listed in stroustrup. I intend to write: // Detect when exactly one of A,B is equal to five. return (A==5) ^^ (B==5); But there is no ^^ operator. Can I use bitwise ^ here and get the right answer (regardless of machine representation of true and false)? I never mix & and &&, or | and ||, so I hesitate to do that with ^ and ^^. I'd be more comfortable writing my own "bool XOR(bool,bool)" function instead.

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• Suppress error with @ operator in PHP

  - by Mez

  In your opinion, is it ever valid to use the @ operator to suppress an error/warning in PHP whereas you may be handling the error? If so, in what circumstances would you use this? Code examples are welcome. Edit: Note to repliers. I'm not looking to turn error reporting off, but, for example, common practice is to use @fopen($file); and then check afterwards... but you can get rid of the @ by doing if (file_exists($file)) { fopen($file); } else { die('File not found'); } or similar. I guess the question is - is there anywhere that @ HAS to be used to supress an error, that CANNOT be handled in any other manner?

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• How to replace a codebehind method with an aspx method using ternary operator

  - by user466663

  I have an asp:hyperlink control as part of a gridview template. The code in the aspx page is given below: asp:HyperLink runat="server" ID="lnkEdit" ToolTip="Edit article" NavigateUrl='<%# GetUrl(Eval("ID").ToString(), Eval("CategoryID").ToString()) %' ImageUrl="~/Images/Edit.gif" The NavigateUrl value is obtained from the codebehind method GetUrl(string, string). The code works fine and is as follows: protected string GetUrl(string id, string categoryID) { var CategoryID = string.Empty; if (!String.IsNullOrEmpty(Request.QueryString["CatID"])) { CategoryID = Request.QueryString["CatID"].ToString(); } else if (!String.IsNullOrEmpty(categoryID)) { CategoryID = categoryID; } return "~/TBSArticles/WriteOrEditArticle.aspx?ID=" + id + "&CatID=" + CategoryID; } I want to replace the code behind method by using a ternary operator within the aspx page. I tried something like below, but didn't work: asp:HyperLink runat="server" ID="lnkEdit" ToolTip="Edit article" NavigateUrl='<%# "~/TBSArticles/WriteOrEditArticle.aspx?ID=" + Eval("ID") + "&CatID=" + Eval(this.Request.QueryString["CatID"].ToString()) != ""? this.Request.QueryString["CatID"] : Eval("CategoryID")) %' ImageUrl="~/Images/Edit.gif" Any help will be greatly appreciated. Thanks

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• C++: Why does gcc prefer non-const over const when accessing operator[]?

  - by JonasW

  This question might be more appropriately asked regarding C++ in general, but as I am using gcc on linux that's the context. Consider the following program: #include <iostream> #include <map> #include <string> using namespace std; template <typename TKey, typename TValue> class Dictionary{ public: map<TKey, TValue> internal; TValue & operator[](TKey const & key) { cout << "operator[] with key " << key << " called " << endl; return internal[key]; } TValue const & operator[](TKey const & key) const { cout << "operator[] const with key " << key << " called " << endl; return internal.at(key); } }; int main(int argc, char* argv[]) { Dictionary<string, string> dict; dict["1"] = "one"; cout << "first one: " << dict["1"] << endl; return 0; } When executing the program, the output is: operator[] with key 1 called operator[] with key 1 called first one: one What I would like is to have the compiler choose the operator[]const method instead in the second call. The reason is that without having used dict["1"] before, the call to operator[] causes the internal map to create the data that does not exist, even if the only thing I wanted was to do some debugging output, which of course is a fatal application error. The behaviour I am looking for would be something like the C# index operator which has a get and a set operation and where you could throw an exception if the getter tries to access something that doesn't exist: class MyDictionary<TKey, TVal> { private Dictionary<TKey, TVal> dict = new Dictionary<TKey, TVal>(); public TVal this[TKey idx] { get { if(!dict.ContainsKey(idx)) throw KeyNotFoundException("..."); return dict[idx]; } set { dict[idx] = value; } } } Thus, I wonder why the gcc prefers the non-const call over the const call when non-const access is not required.

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• Why operator= returns reference not const reference

  - by outmind

  The original question is related to overloading operator= and I like to share my findings as it was nontrivial for me to find them. I cannot imagine reasonable example to use (a=b) as lvalue. With the help of IRC and google I've found the next article: http://msdn.microsoft.com/en-us/magazine/cc301415.aspx it provides two examples. (a=b)=c f(T& ); f(a=b) but both a bit not good, as first violate associativity and I believe that it is bad practice. The second one give me the same feeling. Could you provide more good examples why it should be non constant?

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• How does the increment operator (++) work on DateTime in C#

  - by sohtimsso1970

  What happens if you use the increment operator (++) on a DateTime type in C#? For instance, if I did this: DateTime blah = new DateTime(2010, 12, 24); blah++; What does blah become? Does that increment by a tick or a day? Or is that even legal? I don't have a dev environment around, and won't for a few days, or I would just try it and find out. I was too curious to wait so I figured I'd ask the community.

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• C# memory allocation

  - by user279691

  Does using operator new in c# might fail (if it requires a large memory)? -Solved- And how to discover it? -Solved- What other failures new operator might throw? Thanks

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• Stream overloading in C++

  - by user265260

  why does void operator<<(ostream out, Test &t); return an error whereas void operator<<(ostream &out, Test &t); does not ?

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• EL syntax error: Expression cannot start with binary operator

  - by auser

  Anyone have any creative ideas for how I can solve this warning? EL syntax error: Expression cannot start with binary operator caused by the following code: String.format("#{myController.deleteItemById(%d)}", getId()) My code looked like this before: "#{myController.deleteItemById(" + getId() + ")}" but this caused eclipse to generate the following warning: EL syntax error: String is not closed UPDATE: @ManagedBean(name = "myController") @ViewScoped public class MyController implements Serializable { private long id; private HtmlPanelGroup panel; public long getId() {return this.id; } private void getPanel() { /// bunch of code for programatically creating a form HtmlCommandButton deleteButton = new HtmlCommandButton(); deleteButton.setId(id); deleteButton.setValue(value); deleteButton.setActionExpression(/* EL expression used here */); } } <?xml version='1.0' encoding='UTF-8' ?> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:h="http://java.sun.com/jsf/html" xmlns:f="http://java.sun.com/jsf/core" xmlns:ui="http://java.sun.com/jsf/facelets"> <!-- some other elements removed for the sake of clarity --> <h:body> <h:panelGroup binding="#{myController.panel}" /> </h:body> </html>

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• "<" operator error

  - by Nona Urbiz

  Why is the ( i < UniqueWords.Count ) expression valid in the for loop, but returns "CS0019 Operator '<' cannot be applied to operands of type 'int' and 'method group'" error when placed in my if? They are both string arrays, previously declared. for (int i = 0;i<UniqueWords.Count;i++){ Occurrences[i] = Words.Where(x => x.Equals(UniqueWords[i])).Count(); Keywords[i] = UniqueWords[i]; if (i<UniqueURLs.Count) {rURLs[i] = UniqueURLs[i];} } EDITED to add declarations: List<string> Words = new List<string>(); List<string> URLs = new List<string>(); //elements added like so. . . . Words.Add (referringWords); //these are strings URLs.Add (referringURL); UniqueWords = Words.Distinct().ToList(); UniqueURLs = URLs.Distinct().ToList(); SOLVED. thank you, parentheses were needed for method .Count() I still do not fully understand why they are not always necessary. Jon Skeet, thanks, I guess I don't understand what exactly the declarations are either then? You wanted the actual values assigned? They are pulled from an external source, but are strings. I get it! Thanks. (the ()'s at least.)

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• getting SIGSEGV in std::_List_const_iterator<Exiv2::Exifdatum>::operator++ whilst using jni

  - by HJED

  Hi I'm using jni to access the exiv2 API in my Java project and I'm getting a SIGSEGV error in std::_List_const_iterator::operator++. I'm uncertain how to fix this error. I've tried using high -Xmx values as well as running on both jdk1.6.0 (server and cacao JVMs) and 1.7.0 (server JVM). gdb traceback: #0 0x00007fffa36f2363 in std::_List_const_iterator<Exiv2::Exifdatum>::operator++ (this=0x7ffff7fd3500) at /usr/include/c++/4.4/bits/stl_list.h:223 #1 0x00007fffa36f2310 in std::__distance<std::_List_const_iterator<Exiv2::Exifdatum> > (__first=..., __last=...) at /usr/include/c++/4.4/bits/stl_iterator_base_funcs.h:79 #2 0x00007fffa36f224d in std::distance<std::_List_const_iterator<Exiv2::Exifdatum> > (__first=..., __last=...) at /usr/include/c++/4.4/bits/stl_iterator_base_funcs.h:114 #3 0x00007fffa36f1f27 in std::list<Exiv2::Exifdatum, std::allocator<Exiv2::Exifdatum> >::size (this=0x7fffa4030910) at /usr/include/c++/4.4/bits/stl_list.h:805 #4 0x00007fffa36f1d50 in Exiv2::ExifData::count (this=0x7fffa4030910) at /usr/local/include/exiv2/exif.hpp:518 #5 0x00007fffa36f1d30 in Exiv2::ExifData::empty (this=0x7fffa4030910) at /usr/local/include/exiv2/exif.hpp:516 #6 0x00007fffa36f1763 in getVars (path=0x7fffa401d2f0 "/home/hjed/PC100001.JPG", env=0x6131c8, obj=0x7ffff7fd37a8) at src/main.cpp:146 #7 0x00007fffa36f19d8 in Java_photo_exiv2_Exiv2MetaDataStore_impl_1loadFromExiv (env=0x6131c8, obj=0x7ffff7fd37a8, path=0x7ffff7fd37a0, obj2=0x7ffff7fd3798) at src/main.cpp:160 #8 0x00007ffff21d9cc8 in ?? () #9 0x00000000fffffffe in ?? () #10 0x00007ffff7fd3740 in ?? () #11 0x0000000000613000 in ?? () #12 0x00007ffff7fd3738 in ?? () #13 0x00007fffaa1076e0 in ?? () #14 0x00007ffff7fd37a8 in ?? () #15 0x00007fffaa108d10 in ?? () #16 0x0000000000000000 in ?? () Java error: # A fatal error has been detected by the Java Runtime Environment: # # SIGSEGV (0xb) at pc=0x00007fac11223363, pid=11905, tid=140378349111040 # # JRE version: 6.0_20-b20 # Java VM: OpenJDK 64-Bit Server VM (19.0-b09 mixed mode linux-amd64 ) # Derivative: IcedTea6 1.9.2 # Distribution: Ubuntu 10.10, package 6b20-1.9.2-0ubuntu2 # Problematic frame: # C [libExiff2-binding.so+0x4363] _ZNSt20_List_const_iteratorIN5Exiv29ExifdatumEEppEv+0xf # # If you would like to submit a bug report, please include # instructions how to reproduce the bug and visit: # https://bugs.launchpad.net/ubuntu/+source/openjdk-6/ # The crash happened outside the Java Virtual Machine in native code. # See problematic frame for where to report the bug. # --------------- T H R E A D --------------- Current thread (0x0000000000dbf000): JavaThread "main" [_thread_in_native, id=11909, stack(0x00007fac61920000,0x00007fac61a21000)] siginfo:si_signo=SIGSEGV: si_errno=0, si_code=128 (), si_addr=0x0000000000000000 Registers: ... Register to memory mapping: RAX=0x6c8948f0245c8948 0x6c8948f0245c8948 is pointing to unknown location RBX=0x00007fac0c042c00 0x00007fac0c042c00 is pointing to unknown location RCX=0x0000000000000000 0x0000000000000000 is pointing to unknown location RDX=0x6c8948f0245c8948 0x6c8948f0245c8948 is pointing to unknown location RSP=0x00007fac61a1f4e0 0x00007fac61a1f4e0 is pointing into the stack for thread: 0x0000000000dbf000 "main" prio=10 tid=0x0000000000dbf000 nid=0x2e85 runnable [0x00007fac61a1f000] java.lang.Thread.State: RUNNABLE RBP=0x00007fac61a1f4e0 0x00007fac61a1f4e0 is pointing into the stack for thread: 0x0000000000dbf000 "main" prio=10 tid=0x0000000000dbf000 nid=0x2e85 runnable [0x00007fac61a1f000] java.lang.Thread.State: RUNNABLE RSI=0x00007fac61a1f4f0 0x00007fac61a1f4f0 is pointing into the stack for thread: 0x0000000000dbf000 "main" prio=10 tid=0x0000000000dbf000 nid=0x2e85 runnable [0x00007fac61a1f000] java.lang.Thread.State: RUNNABLE RDI=0x00007fac61a1f500 0x00007fac61a1f500 is pointing into the stack for thread: 0x0000000000dbf000 "main" prio=10 tid=0x0000000000dbf000 nid=0x2e85 runnable [0x00007fac61a1f000] java.lang.Thread.State: RUNNABLE R8 =0x00007fac0c054630 0x00007fac0c054630 is pointing to unknown location R9 =0x00007fac61a1f358 0x00007fac61a1f358 is pointing into the stack for thread: 0x0000000000dbf000 "main" prio=10 tid=0x0000000000dbf000 nid=0x2e85 runnable [0x00007fac61a1f000] java.lang.Thread.State: RUNNABLE R10=0x00007fac61a1f270 0x00007fac61a1f270 is pointing into the stack for thread: 0x0000000000dbf000 "main" prio=10 tid=0x0000000000dbf000 nid=0x2e85 runnable [0x00007fac61a1f000] java.lang.Thread.State: RUNNABLE R11=0x00007fac11223354 0x00007fac11223354: _ZNSt20_List_const_iteratorIN5Exiv29ExifdatumEEppEv+0 in /home/hjed/libExiff2-binding.so at 0x00007fac1121f000 R12=0x0000000000dbf000 "main" prio=10 tid=0x0000000000dbf000 nid=0x2e85 runnable [0x00007fac61a1f000] java.lang.Thread.State: RUNNABLE R13=0x00007fac13ad1be8 {method} - klass: {other class} R14=0x00007fac61a1f7a8 0x00007fac61a1f7a8 is pointing into the stack for thread: 0x0000000000dbf000 "main" prio=10 tid=0x0000000000dbf000 nid=0x2e85 runnable [0x00007fac61a1f000] java.lang.Thread.State: RUNNABLE R15=0x0000000000dbf000 "main" prio=10 tid=0x0000000000dbf000 nid=0x2e85 runnable [0x00007fac61a1f000] java.lang.Thread.State: RUNNABLE Top of Stack: (sp=0x00007fac61a1f4e0) ... Instructions: (pc=0x00007fac11223363) ... Stack: [0x00007fac61920000,0x00007fac61a21000], sp=0x00007fac61a1f4e0, free space=1021k Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code) C [libExiff2-binding.so+0x4363] _ZNSt20_List_const_iteratorIN5Exiv29ExifdatumEEppEv+0xf C [libExiff2-binding.so+0x4310] _ZSt10__distanceISt20_List_const_iteratorIN5Exiv29ExifdatumEEENSt15iterator_traitsIT_E15difference_typeES5_S5_St18input_iterator_tag+0x26 C [libExiff2-binding.so+0x424d] _ZSt8distanceISt20_List_const_iteratorIN5Exiv29ExifdatumEEENSt15iterator_traitsIT_E15difference_typeES5_S5_+0x36 C [libExiff2-binding.so+0x3f27] _ZNKSt4listIN5Exiv29ExifdatumESaIS1_EE4sizeEv+0x33 C [libExiff2-binding.so+0x3d50] _ZNK5Exiv28ExifData5countEv+0x18 C [libExiff2-binding.so+0x3d30] _ZNK5Exiv28ExifData5emptyEv+0x18 C [libExiff2-binding.so+0x3763] _Z7getVarsPKcP7JNIEnv_P8_jobject+0x3e3 C [libExiff2-binding.so+0x39d8] Java_photo_exiv2_Exiv2MetaDataStore_impl_1loadFromExiv+0x4b j photo.exiv2.Exiv2MetaDataStore.impl_loadFromExiv(Ljava/lang/String;Lphoto/exiv2/Exiv2MetaDataStore;)V+0 j photo.exiv2.Exiv2MetaDataStore.loadFromExiv2()V+9 j photo.exiv2.Exiv2MetaDataStore.loadData()V+1 j photo.exiv2.Exiv2MetaDataStore.<init>(Lphoto/ImageFile;)V+10 j photo.ImageFile.<init>(Ljava/lang/String;)V+11 j test.Main.main([Ljava/lang/String;)V+67 v ~StubRoutines::call_stub V [libjvm.so+0x428698] V [libjvm.so+0x4275c8] V [libjvm.so+0x432943] V [libjvm.so+0x447f91] C [java+0x3495] JavaMain+0xd75 Java frames: (J=compiled Java code, j=interpreted, Vv=VM code) j photo.exiv2.Exiv2MetaDataStore.impl_loadFromExiv(Ljava/lang/String;Lphoto/exiv2/Exiv2MetaDataStore;)V+0 j photo.exiv2.Exiv2MetaDataStore.loadFromExiv2()V+9 j photo.exiv2.Exiv2MetaDataStore.loadData()V+1 j photo.exiv2.Exiv2MetaDataStore.<init>(Lphoto/ImageFile;)V+10 j photo.ImageFile.<init>(Ljava/lang/String;)V+11 j test.Main.main([Ljava/lang/String;)V+67 v ~StubRoutines::call_stub --------------- P R O C E S S --------------- Java Threads: ( => current thread ) 0x00007fac0c028000 JavaThread "Low Memory Detector" daemon [_thread_blocked, id=11924, stack(0x00007fac11532000,0x00007fac11633000)] 0x00007fac0c025800 JavaThread "CompilerThread1" daemon [_thread_blocked, id=11923, stack(0x00007fac11633000,0x00007fac11734000)] 0x00007fac0c022000 JavaThread "CompilerThread0" daemon [_thread_blocked, id=11922, stack(0x00007fac11734000,0x00007fac11835000)] 0x00007fac0c01f800 JavaThread "Signal Dispatcher" daemon [_thread_blocked, id=11921, stack(0x00007fac11835000,0x00007fac11936000)] 0x00007fac0c001000 JavaThread "Finalizer" daemon [_thread_blocked, id=11920, stack(0x00007fac11e2d000,0x00007fac11f2e000)] 0x0000000000e36000 JavaThread "Reference Handler" daemon [_thread_blocked, id=11919, stack(0x00007fac11f2e000,0x00007fac1202f000)] =>0x0000000000dbf000 JavaThread "main" [_thread_in_native, id=11909, stack(0x00007fac61920000,0x00007fac61a21000)] Other Threads: 0x0000000000e2f800 VMThread [stack: 0x00007fac1202f000,0x00007fac12130000] [id=11918] 0x00007fac0c02b000 WatcherThread [stack: 0x00007fac11431000,0x00007fac11532000] [id=11925] ... Heap PSYoungGen total 18432K, used 632K [0x00007fac47210000, 0x00007fac486a0000, 0x00007fac5bc10000) eden space 15808K, 4% used [0x00007fac47210000,0x00007fac472ae188,0x00007fac48180000) from space 2624K, 0% used [0x00007fac48410000,0x00007fac48410000,0x00007fac486a0000) to space 2624K, 0% used [0x00007fac48180000,0x00007fac48180000,0x00007fac48410000) PSOldGen total 42240K, used 0K [0x00007fac1de10000, 0x00007fac20750000, 0x00007fac47210000) object space 42240K, 0% used [0x00007fac1de10000,0x00007fac1de10000,0x00007fac20750000) PSPermGen total 21248K, used 2831K [0x00007fac13810000, 0x00007fac14cd0000, 0x00007fac1de10000) object space 21248K, 13% used [0x00007fac13810000,0x00007fac13ad3d80,0x00007fac14cd0000) Dynamic libraries: ... VM Arguments: jvm_args: -Dfile.encoding=UTF-8 java_command: test.Main Launcher Type: SUN_STANDARD Environment Variables: PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games USERNAME=hjed LD_LIBRARY_PATH=/usr/lib/jvm/java-6-openjdk/jre/lib/amd64/server:/usr/lib/jvm/java-6-openjdk/jre/lib/amd64:/usr/lib/jvm/java-6-openjdk/jre/../lib/amd64 SHELL=/bin/bash DISPLAY=:0.0 Signal Handlers: ... --------------- S Y S T E M --------------- OS:Ubuntu 10.10 (maverick) uname:Linux 2.6.35-24-generic #42-Ubuntu SMP Thu Dec 2 02:41:37 UTC 2010 x86_64 libc:glibc 2.12.1 NPTL 2.12.1 rlimit: STACK 8192k, CORE 0k, NPROC infinity, NOFILE 1024, AS infinity load average:0.27 0.31 0.30 /proc/meminfo: MemTotal: 4048200 kB MemFree: 106552 kB Buffers: 838212 kB Cached: 1172496 kB SwapCached: 0 kB Active: 1801316 kB Inactive: 1774880 kB Active(anon): 1224708 kB Inactive(anon): 355012 kB Active(file): 576608 kB Inactive(file): 1419868 kB Unevictable: 64 kB Mlocked: 64 kB SwapTotal: 7065596 kB SwapFree: 7065596 kB Dirty: 20 kB Writeback: 0 kB AnonPages: 1565608 kB Mapped: 213424 kB Shmem: 14216 kB Slab: 164812 kB SReclaimable: 102576 kB SUnreclaim: 62236 kB KernelStack: 4784 kB PageTables: 44908 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 9089696 kB Committed_AS: 3676872 kB VmallocTotal: 34359738367 kB VmallocUsed: 332952 kB VmallocChunk: 34359397884 kB HardwareCorrupted: 0 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB DirectMap4k: 48704 kB DirectMap2M: 4136960 kB CPU:total 8 (4 cores per cpu, 2 threads per core) family 6 model 26 stepping 5, cmov, cx8, fxsr, mmx, sse, sse2, sse3, ssse3, sse4.1, sse4.2, popcnt, ht Memory: 4k page, physical 4048200k(106552k free), swap 7065596k(7065596k free) vm_info: OpenJDK 64-Bit Server VM (19.0-b09) for linux-amd64 JRE (1.6.0_20-b20), built on Dec 10 2010 19:45:55 by "buildd" with gcc 4.4.5 main.cpp: jobject toJava(std::auto_ptr<Exiv2::Value> v, const char * type, JNIEnv * env) { jclass stringClass; jmethodID cid; jobject result; stringClass = env->FindClass("photo/exiv2/Value"); cid = env->GetMethodID(stringClass, "<init>", "(Ljava/lang/String;Ljava/lang/Object;)V"); jvalue val; if ((strcmp(type, "String") == 0) || (strcmp(type, "String") == 0)) { val.l = env->NewStringUTF(v->toString().c_str()); } else if (strcmp(type, "Short") == 0) { val.s = v->toLong(0); } else if (strcmp(type, "Long") == 0) { val.j = v->toLong(0); } result = env->NewObject(stringClass, cid, env->NewStringUTF(v->toString().c_str()), val); return result; } void inLoop(std::auto_ptr<MetadataContainer> md, JNIEnv * env, jmethodID mid, jobject obj) { jvalue values[2]; const char* key = md->key().c_str(); values[0].l = env->NewStringUTF(key); /** md->value().toString().c_str(); const char* value = md->typeName(); values[1].l = env->NewStringUTF(value); TODO: do type conversions */ //std::cout << md->typeName() << std::endl; /** const char* type = md->value().toString().c_str(); values[1].l = env->NewStringUTF(type);*/ values[1].l = toJava(md->getValue(), md->typeName(), env); env->CallVoidMethodA(obj, mid, values); } void getVars(const char* path, JNIEnv * env, jobject obj) { //Load image Exiv2::Image::AutoPtr image = Exiv2::ImageFactory::open(path); assert(image.get() != 0); image->readMetadata(); //load method jclass cls = env->GetObjectClass(obj); jmethodID mid = env->GetMethodID(cls, "exiv2_reciveElement", "(Ljava/lang/String;Lphoto/exiv2/Value;)V"); //Load IPTC data /**loadIPTC(image, path, env, obj, mid); loadEXIF(image, path, env, obj, mid);*/ Exiv2::IptcData &iptcData = image->iptcData(); if (mid != NULL) { //is there any IPTC data AND check that method exists if (iptcData.empty()) { std::string error(path); error += ": failed loading IPTC data, there may not be any data"; } else { Exiv2::IptcData::iterator end = iptcData.end(); for (Exiv2::IptcData::iterator md = iptcData.begin(); md != end; ++md) { std::auto_ptr<MetadataContainer> meta(new MetadataContainer(md)); inLoop(meta, env, mid, obj); } } Exiv2::ExifData &exifData = image->exifData(); //is there any Exif data AND check that method exists if (exifData.empty()) { //error occurs here (main.cpp:146) std::string error(path); error += ": failed loading Exif data, there may not be any data"; } else { Exiv2::ExifData::iterator end = exifData.end(); for (Exiv2::ExifData::iterator md = exifData.begin(); md != end; ++md) { std::auto_ptr<MetadataContainer> meta(new MetadataContainer(md)); inLoop(meta, env, mid, obj); } } } else { std::string error(path); error += ": failed to load method"; } } JNIEXPORT void JNICALL Java_photo_exiv2_Exiv2MetaDataStore_impl_1loadFromExiv(JNIEnv * env, jobject obj, jstring path, jobject obj2) { const char* path2 = env->GetStringUTFChars(path, NULL); getVars(path2, env, obj); env->ReleaseStringUTFChars(path, path2); } Thanks for any help, HJED EDIT This is the output when runing the jvm with the -cacao option: run: null:/usr/local/lib Error: Directory Olympus2 with 1536 entries considered invalid; not read. LOG: [0x00007ff005376700] We received a SIGSEGV and tried to handle it, but we were LOG: [0x00007ff005376700] unable to find a Java method at: LOG: [0x00007ff005376700] LOG: [0x00007ff005376700] PC=0x00007feffe4ee67d LOG: [0x00007ff005376700] LOG: [0x00007ff005376700] Dumping the current stacktrace: at photo.exiv2.Exiv2MetaDataStore.impl_loadFromExiv(Ljava/lang/String;Lphoto/exiv2/Exiv2MetaDataStore;)V(Native Method) at photo.exiv2.Exiv2MetaDataStore.loadFromExiv2()V(Exiv2MetaDataStore.java:38) at photo.exiv2.Exiv2MetaDataStore.loadData()V(Exiv2MetaDataStore.java:29) at photo.exiv2.MetaDataStore.<init>(Lphoto/ImageFile;)V(MetaDataStore.java:33) at photo.exiv2.Exiv2MetaDataStore.<init>(Lphoto/ImageFile;)V(Exiv2MetaDataStore.java:20) at photo.ImageFile.<init>(Ljava/lang/String;)V(ImageFile.java:22) at test.Main.main([Ljava/lang/String;)V(Main.java:28) LOG: [0x00007ff005376700] vm_abort: WARNING, port me to C++ and use os::abort() instead. LOG: [0x00007ff005376700] Exiting... LOG: [0x00007ff005376700] Backtrace (15 stack frames): LOG: [0x00007ff005376700] /usr/lib/jvm/java-6-openjdk/jre/lib/amd64/cacao/libjvm.so(+0x4ff54) [0x7ff004306f54] LOG: [0x00007ff005376700] /usr/lib/jvm/java-6-openjdk/jre/lib/amd64/cacao/libjvm.so(+0x5ac01) [0x7ff004311c01] LOG: [0x00007ff005376700] /usr/lib/jvm/java-6-openjdk/jre/lib/amd64/cacao/libjvm.so(+0x66e9a) [0x7ff00431de9a] LOG: [0x00007ff005376700] /usr/lib/jvm/java-6-openjdk/jre/lib/amd64/cacao/libjvm.so(+0x76408) [0x7ff00432d408] LOG: [0x00007ff005376700] /usr/lib/jvm/java-6-openjdk/jre/lib/amd64/cacao/libjvm.so(+0x79a4c) [0x7ff004330a4c] LOG: [0x00007ff005376700] /lib/libpthread.so.0(+0xfb40) [0x7ff004d53b40] LOG: [0x00007ff005376700] /home/hjed/libExiff2-binding.so(_ZNSt20_List_const_iteratorIN5Exiv29ExifdatumEEppEv+0xf) [0x7feffe4ee67d] LOG: [0x00007ff005376700] /home/hjed/libExiff2-binding.so(_ZSt10__distanceISt20_List_const_iteratorIN5Exiv29ExifdatumEEENSt15iterator_traitsIT_E15difference_typeES5_S5_St18input_iterator_tag+0x26) [0x7feffe4ee62a] LOG: [0x00007ff005376700] /home/hjed/libExiff2-binding.so(_ZSt8distanceISt20_List_const_iteratorIN5Exiv29ExifdatumEEENSt15iterator_traitsIT_E15difference_typeES5_S5_+0x36) [0x7feffe4ee567] LOG: [0x00007ff005376700] /home/hjed/libExiff2-binding.so(_ZNKSt4listIN5Exiv29ExifdatumESaIS1_EE4sizeEv+0x33) [0x7feffe4ee22b] LOG: [0x00007ff005376700] /home/hjed/libExiff2-binding.so(_ZNK5Exiv28ExifData5countEv+0x18) [0x7feffe4ee054] LOG: [0x00007ff005376700] /home/hjed/libExiff2-binding.so(_ZNK5Exiv28ExifData5emptyEv+0x18) [0x7feffe4ee034] LOG: [0x00007ff005376700] /home/hjed/libExiff2-binding.so(_Z7getVarsPKcP7JNIEnv_P8_jobject+0x3d7) [0x7feffe4ed947] LOG: [0x00007ff005376700] /home/hjed/libExiff2-binding.so(Java_photo_exiv2_Exiv2MetaDataStore_impl_1loadFromExiv+0x4b) [0x7feffe4edcdc] LOG: [0x00007ff005376700] [0x7feffe701ccd] Java Result: 134 BUILD SUCCESSFUL (total time: 0 seconds)

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• F# passing an operator with arguments to a function

  - by dan

  Can you pass in an operation like "divide by 2" or "subtract 1" using just a partially applied operator, where "add 1" looks like this: List.map ((+) 1) [1..5];; //equals [2..6] // instead of having to write: List.map (fun x-> x+1) [1..5] What's happening is 1 is being applied to (+) as it's first argument, and the list item is being applied as the second argument. For addition and multiplication, this argument ordering doesn't matter. Suppose I want to subtract 1 from every element (this will probably be a common beginners mistake): List.map ((-) 1) [1..5];; //equals [0 .. -4], the opposite of what we wanted 1 is applied to the (-) as its first argument, so instead of (list_item - 1), I get (1 - list_item). I can rewrite it as adding negative one instead of subtracting positive one: List.map ((+) -1) [1..5];; List.map (fun x -> x-1) [1..5];; // this works too I'm looking for a more expressive way to write it, something like ((-) _ 1), where _ denotes a placeholder, like in the Arc language. This would cause 1 to be the second argument to -, so in List.map, it would evaluate to list_item - 1. So if you wanted to map divide by 2 to the list, you could write: List.map ((/) _ 2) [2;4;6] //not real syntax, but would equal [1;2;3] List.map (fun x -> x/2) [2;4;6] //real syntax equivalent of the above Can this be done or do I have to use (fun x -> x/2)? It seems that the closest we can get to the placeholder syntax is to use a lambda with a named argument.

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• ruby comma operator and step question

  - by ryan_m

  so, i'm trying to learn ruby by doing some project euler questions, and i've run into a couple things i can't explain, and the comma ?operator? is in the middle of both. i haven't been able to find good documentation for this, maybe i'm just not using the google as I should, but good ruby documentation seems a little sparse . . . 1: how do you describe how this is working? the first snippet is the ruby code i don't understand, the second is the code i wrote that does the same thing only after painstakingly tracing the first: #what is this doing? cur, nxt = nxt, cur + nxt #this, apparently, but how to describe the above? nxt = cur + nxt cur = nxt - cur 2: in the following example, how do you describe what the line with 'step' is doing? from what i can gather, the step command works like (range).step(step_size), but this seems to be doing (starting_point).step(ending_point, step_size). Am i right with this assumption? where do i find good doc of this? #/usr/share/doc/ruby1.9.1-examples/examples/sieve.rb # sieve of Eratosthenes max = Integer(ARGV.shift || 100) sieve = [] for i in 2 .. max sieve[i] = i end for i in 2 .. Math.sqrt(max) next unless sieve[i] (i*i).step(max, i) do |j| sieve[j] = nil end end puts sieve.compact.join(", ")

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• The new operator in C# isn't overriding base class member

  - by Dominic Zukiewicz

  I am confused as to why the new operator isn't working as I expected it to. Note: All classes below are defined in the same namespace, and in the same file. This class allows you to prefix any content written to the console with some provided text. public class ConsoleWriter { private string prefix; public ConsoleWriter(string prefix) { this.prefix = prefix; } public void Write(string text) { Console.WriteLine(String.Concat(prefix,text)); } } Here is a base class: public class BaseClass { protected static ConsoleWriter consoleWriter = new ConsoleWriter(""); public static void Write(string text) { consoleWriter.Write(text); } } Here is an implemented class: public class NewClass : BaseClass { protected new static ConsoleWriter consoleWriter = new ConsoleWriter("> "); } Now here's the code to execute this: class Program { static void Main(string[] args) { BaseClass.Write("Hello World!"); NewClass.Write("Hello World!"); Console.Read(); } } So I would expect the output to be Hello World! > Hello World! But the output is Hello World Hello World I do not understand why this is happening. Here is my thought process as to what is happening: The CLR calls the BaseClass.Write() method The CLR initialises the BaseClass.consoleWriter member. The method is called and executed with the BaseClass.consoleWriter variable Then The CLR calls the NewClass.Write() The CLR initialises the NewClass.consoleWriter object. The CLR sees that the implementation lies in BaseClass, but the method is inherited through The CLR executes the method locally (in NewClass) using the NewClass.consoleWriter variable I thought this is how the inheritance structure works? Please can someone help me understand why this is not working?

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• "The data types text and nvarchar are incompatible in the equal to operator" in SQL Query

  - by kenom

  Why i get this error: The data types text and nvarchar are incompatible in the equal to operator. The field of "username" in database is text type... This is my soruce: <%@ Control Language="C#" AutoEventWireup="true" CodeFile="my_answers.ascx.cs" Inherits="kontrole_login_my_answers" %> <div style=" margin-top:-1280px; float:left;"> <p></p> <div id="question"> Add question </div> </div> <asp:GridView ID="GridView1" runat="server" DataSourceID="SqlDataSource1" > </asp:GridView> <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:estudent_piooConnectionString %>" SelectCommand="SELECT * FROM [question] WHERE ([username] = @fafa)"> <SelectParameters> <asp:QueryStringParameter Name="fafa" QueryStringField="user" Type="String"/> </SelectParameters> </asp:SqlDataSource>

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• Ternary operator

  - by Antoine Leclair

  In PHP, I often use the ternary operator to add an attribute to an html element if it applies to the element in question. For example: <select name="blah"> <option value="1"<?= $blah == 1 ? ' selected="selected"' : '' ?>> One </option> <option value="2"<?= $blah == 2 ? ' selected="selected"' : '' ?>> Two </option> </select> I'm starting a project with Pylons using Mako for the templating. How can I achieve something similar? Right now, I see two possibilities that are not ideal. Solution 1: <select name="blah"> % if blah == 1: <option value="1" selected="selected">One</option> % else: <option value="1">One</option> % endif % if blah == 2: <option value="2" selected="selected">Two</option> % else: <option value="2">Two</option> % endif </select> Solution 2: <select name="blah"> <option value="1" % if blah == 1: selected="selected" % endif >One</option> <option value="2" % if blah == 2: selected="selected" % endif >Two</option> </select> In this particular case, the value is equal to the variable tested (value="1" = blah == 1), but I use the same pattern in other situations, like <?= isset($variable) ? ' value="$variable" : '' ?>. I am looking for a clean way to achieve this using Mako.

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