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  • How does Ruby's Enumerator object iterate externally over an internal iterator?

    - by Salman Paracha
    As per Ruby's documentation, the Enumerator object uses the each method (to enumerate) if no target method is provided to the to_enum or enum_for methods. Now, let's take the following monkey patch and its enumerator, as an example o = Object.new def o.each yield 1 yield 2 yield 3 end e = o.to_enum loop do puts e.next end Given that the Enumerator object uses the each method to answer when next is called, how do calls to the each method look like, every time next is called? Does the Enumeartor class pre-load all the contents of o.each and creates a local copy for enumeration? Or is there some sort of Ruby magic that hangs the operations at each yield statement until next is called on the enumeartor? If an internal copy is made, is it a deep copy? What about I/O objects that could be used for external enumeration? I'm using Ruby 1.9.2.

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  • Python file iterator over a binary file with newer idiom.

    - by drewk
    In Python, for a binary file, I can write this: buf_size=1024*64 # this is an important size... with open(file, "rb") as f: while True: data=f.read(buf_size) if not data: break # deal with the data.... With a text file that I want to read line-by-line, I can write this: with open(file, "r") as file: for line in file: # deal with each line.... Which is shorthand for: with open(file, "r") as file: for line in iter(file.readline, ""): # deal with each line.... This idiom is documented in PEP 234 but I have failed to locate a similar idiom for binary files. I have tried this: >>> with open('dups.txt','rb') as f: ... for chunk in iter(f.read,''): ... i+=1 >>> i 1 # 30 MB file, i==1 means read in one go... I tried putting iter(f.read(buf_size),'') but that is a syntax error because of the parens after the callable in iter(). I know I could write a function, but is there way with the default idiom of for chunk in file: where I can use a buffer size versus a line oriented? Thanks for putting up with the Python newbie trying to write his first non-trivial and idiomatic Python script.

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  • How can I make an iterator that never ends?

    - by Soldier.moth
    I was just wondering what the easiest way to iterate over a set indefinitely, i.e. when it reaches the end it next(); calls the first object. I'm assuming that this is not an already predefined function in Java, so just looking for the easiest way to implement this in Java.

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  • How can I have a Foo* iterator to a vector of Foo?

    - by mghie
    If I have a class that contains a std::list<Foo>, how can I implement iterators to a Foo* collection, preferably without using boost? I'd rather not maintain a parallel collection of pointers. For now I have std::list<Foo>, mostly so that removing or inserting an element does not invalidate all other iterators, but would it be possible to implement other iterators too, so that the collection type used in the implementation is opaque to the user of the class?

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  • Having trouble compiling with GDI+ (VC++ 2008)

    - by user146780
    I just simply include gdiplus.h and get all these errors: Warning 32 warning C4229: anachronism used : modifiers on data are ignored c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1133 Warning 38 warning C4229: anachronism used : modifiers on data are ignored c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1139 Warning 49 warning C4229: anachronism used : modifiers on data are ignored c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1286 Warning 55 warning C4229: anachronism used : modifiers on data are ignored c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1292 Warning 61 warning C4229: anachronism used : modifiers on data are ignored c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2224 Warning 68 warning C4229: anachronism used : modifiers on data are ignored c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2262 Warning 74 warning C4229: anachronism used : modifiers on data are ignored c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2310 Warning 82 warning C4229: anachronism used : modifiers on data are ignored c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2321 Error 112 fatal error C1003: error count exceeds 100; stopping compilation c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 236 Error 1 error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft sdks\windows\v7.0\include\gdiplusimaging.h 74 Error 7 error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft sdks\windows\v7.0\include\gdiplusimaging.h 280 Error 8 error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft sdks\windows\v7.0\include\gdiplusimaging.h 280 Error 94 error C2761: '{ctor}' : member function redeclaration not allowed c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 195 Error 102 error C2761: '{ctor}' : member function redeclaration not allowed c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 212 Error 110 error C2761: '{ctor}' : member function redeclaration not allowed c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 231 Error 21 error C2535: 'Gdiplus::Metafile::Metafile(void)' : member function already defined or declared c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 813 Error 23 error C2535: 'Gdiplus::Metafile::Metafile(void)' : member function already defined or declared c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 820 Error 25 error C2535: 'Gdiplus::Metafile::Metafile(void)' : member function already defined or declared c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 829 Error 27 error C2535: 'Gdiplus::Metafile::Metafile(void)' : member function already defined or declared c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 923 Error 16 error C2535: 'Gdiplus::Image::Image(void)' : member function already defined or declared c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 471 Error 4 error C2470: 'IImageBytes' : looks like a function definition, but there is no parameter list; skipping apparent body c:\program files\microsoft sdks\windows\v7.0\include\gdiplusimaging.h 74 Error 89 error C2448: 'Gdiplus::Metafile::{ctor}' : function-style initializer appears to be a function definition c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 76 Error 97 error C2447: '{' : missing function header (old-style formal list?) c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 199 Error 105 error C2447: '{' : missing function header (old-style formal list?) c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 218 Error 2 error C2440: 'initializing' : cannot convert from 'const char [37]' to 'int' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusimaging.h 74 Error 72 error C2275: 'HDC' : illegal use of this type as an expression c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2310 Error 76 error C2275: 'HDC' : illegal use of this type as an expression c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2310 Error 80 error C2275: 'HDC' : illegal use of this type as an expression c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2321 Error 84 error C2275: 'HDC' : illegal use of this type as an expression c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2321 Error 92 error C2275: 'HDC' : illegal use of this type as an expression c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 195 Error 100 error C2275: 'HDC' : illegal use of this type as an expression c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 212 Error 108 error C2275: 'HDC' : illegal use of this type as an expression c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 231 Error 60 error C2275: 'Gdiplus::MetafileHeader' : illegal use of this type as an expression c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2224 Error 67 error C2275: 'Gdiplus::GpMetafile' : illegal use of this type as an expression c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2262 Error 31 error C2275: 'Gdiplus::GpImage' : illegal use of this type as an expression c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1133 Error 37 error C2275: 'Gdiplus::GpImage' : illegal use of this type as an expression c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1139 Error 48 error C2275: 'Gdiplus::GpBitmap' : illegal use of this type as an expression c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1286 Error 54 error C2275: 'Gdiplus::GpBitmap' : illegal use of this type as an expression c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1292 Error 3 error C2146: syntax error : missing ';' before identifier 'IImageBytes' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusimaging.h 74 Error 6 error C2146: syntax error : missing ';' before identifier 'id' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusimaging.h 280 Error 73 error C2146: syntax error : missing ')' before identifier 'referenceHdc' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2310 Error 81 error C2146: syntax error : missing ')' before identifier 'referenceHdc' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2321 Error 93 error C2146: syntax error : missing ')' before identifier 'referenceHdc' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 195 Error 101 error C2146: syntax error : missing ')' before identifier 'referenceHdc' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 212 Error 109 error C2146: syntax error : missing ')' before identifier 'referenceHdc' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 231 Error 96 error C2143: syntax error : missing ';' before '{' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 199 Error 104 error C2143: syntax error : missing ';' before '{' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 218 Error 33 error C2078: too many initializers c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1133 Error 39 error C2078: too many initializers c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1139 Error 50 error C2078: too many initializers c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1286 Error 56 error C2078: too many initializers c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1292 Error 62 error C2078: too many initializers c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2224 Error 69 error C2078: too many initializers c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2262 Error 75 error C2078: too many initializers c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2310 Error 83 error C2078: too many initializers c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2321 Error 29 error C2065: 'stream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1133 Error 35 error C2065: 'stream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1139 Error 46 error C2065: 'stream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1286 Error 52 error C2065: 'stream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1292 Error 58 error C2065: 'stream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2222 Error 65 error C2065: 'stream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2262 Error 71 error C2065: 'stream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2309 Error 79 error C2065: 'stream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2320 Error 88 error C2065: 'stream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 75 Error 91 error C2065: 'stream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 194 Error 99 error C2065: 'stream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 211 Error 107 error C2065: 'stream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 230 Error 66 error C2065: 'metafile' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2262 Error 28 error C2065: 'IStream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1133 Error 34 error C2065: 'IStream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1139 Error 45 error C2065: 'IStream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1286 Error 51 error C2065: 'IStream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1292 Error 57 error C2065: 'IStream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2222 Error 64 error C2065: 'IStream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2262 Error 70 error C2065: 'IStream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2309 Error 78 error C2065: 'IStream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2320 Error 87 error C2065: 'IStream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 75 Error 90 error C2065: 'IStream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 194 Error 98 error C2065: 'IStream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 211 Error 106 error C2065: 'IStream' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 230 Error 30 error C2065: 'image' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1133 Error 36 error C2065: 'image' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1139 Error 59 error C2065: 'header' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2224 Error 47 error C2065: 'bitmap' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1286 Error 53 error C2065: 'bitmap' : undeclared identifier c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1292 Error 12 error C2061: syntax error : identifier 'PROPID' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 443 Error 13 error C2061: syntax error : identifier 'PROPID' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 444 Error 14 error C2061: syntax error : identifier 'PROPID' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 445 Error 15 error C2061: syntax error : identifier 'PROPID' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 453 Error 41 error C2061: syntax error : identifier 'PROPID' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1244 Error 42 error C2061: syntax error : identifier 'PROPID' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1247 Error 43 error C2061: syntax error : identifier 'PROPID' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1250 Error 44 error C2061: syntax error : identifier 'PROPID' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1262 Error 9 error C2061: syntax error : identifier 'IStream' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 384 Error 10 error C2061: syntax error : identifier 'IStream' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 395 Error 11 error C2061: syntax error : identifier 'IStream' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 405 Error 17 error C2061: syntax error : identifier 'IStream' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 505 Error 18 error C2061: syntax error : identifier 'IStream' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 516 Error 19 error C2061: syntax error : identifier 'IStream' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 758 Error 20 error C2061: syntax error : identifier 'IStream' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 813 Error 22 error C2061: syntax error : identifier 'IStream' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 820 Error 24 error C2061: syntax error : identifier 'IStream' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 829 Error 26 error C2061: syntax error : identifier 'IStream' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusheaders.h 855 Error 40 error C2061: syntax error : identifier 'IStream' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 1156 Error 63 error C2061: syntax error : identifier 'IStream' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2242 Error 86 error C2061: syntax error : identifier 'byte' c:\program files\microsoft sdks\windows\v7.0\include\gdipluspath.h 133 Error 5 error C2059: syntax error : 'public' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusimaging.h 74 Error 77 error C2059: syntax error : ')' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2316 Error 85 error C2059: syntax error : ')' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusflat.h 2327 Error 95 error C2059: syntax error : ')' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 198 Error 103 error C2059: syntax error : ')' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 217 Error 111 error C2059: syntax error : ')' c:\program files\microsoft sdks\windows\v7.0\include\gdiplusmetafile.h 236 I tried updating my sdk to 7.0 but it did not help. I'm not even making any calls to the API. Thanks

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  • C++ Template Iterator error

    - by gprime
    I am going over some code i wrote in 2006 as an undergrad. It's a simple genetic algorithm library written in C++ using templates. It use to work in 2006 when i coded it with visual studio, but now when i am trying to run it in xcode i get compile errors. This function is giving me errors: friend bool operator==(const TSPGenome<T> & t1, const TSPGenome<T> & t2) { // loop through each interator and check to see if the two genomes have the same values if(t1.genome_vec->size() != t2.genome_vec->size()) return false; else { // iterate through each vector<T>::iterator it_t1; vector<T>::iterator it_t2; it_t1 = t1.genome_vec->begin(); for(it_t2 = t2.genome_vec->begin(); it_t2 != t2.genome_vec->end(); ++it_t2, ++it_t1) { if(*it_t2 != *it_t1) return false; } } // everything seems good return true; } xcode complains about these two lines not having ; before it_t1 and it_t2. vector<T>::iterator it_t1; vector<T>::iterator it_t2; Is it because the vector type it T? I declared it in the class as follows: template <typename T> class TSPGenome : public Genome { Any help would be appreciated. Thanks!

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  • Read from cin or a file

    - by m42a
    When I try to compile the code istream in; if (argc==1) in=cin; else { ifstream ifn(argv[1]); in=ifn; } gcc fails, complaining that operator= is private. Is there any way to set an istream to different values based on a condition?

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  • PHP, when to use iterators, how to buffer results?

    - by Jon L.
    When is it best to use Iterators in PHP, and how can they be implemented to best avoid loading all objects into memory simultaneously? Do any constructs exist in PHP so that we can queue up results of an operation for use with an Iterator, while again avoiding loading all objects into memory simultaneously? An example would be a curl HTTP request against a REST server In the case of an HTTP request that returns all results at once (a la curl), would we be better off to go with streaming results, and if so, are there any limitations or pitfalls to be aware of? If using streaming, is it better to replace curl with a PHP native stream/socket? My intention is to implement Iterators for a REST client, and separately a document ORM that I'm maintaining, but only if I can do so while gaining benefits from reduced memory usage, increased performance, etc. Thanks in advance for any responses :-)

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  • Java->Scala Remove Iterator<T>-Element from a JavaConversions-wrapped Iterable

    - by ifischer
    I have to translate the following code from Java to Scala: for (Iterator<ExceptionQueuedEvent> i = getUnhandledExceptionQueuedEvents().iterator(); i.hasNext();) { ExceptionQueuedEvent event = i.next(); try { //do something } finally { i.remove(); } } I'm using the JavaConversions library to wrap the Iterable. But as i'm not using the original Iterator, i don't know how to remove the current element correctly from the collection the same way as i did in Java: import scala.collection.JavaConversions._ (...) for (val event <- events) { try { //do something } finally { //how can i remove the current event from events? } } Can someone help me? I guess it's easy, but i'm still kinda new to Scala and don't understand what's going on when Scala wraps something of Java.

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  • StreamTokenizer Iterator Adapter help

    - by alpdog14
    I have this StreamTokenizer Iterator Adapter that is suppose to create a Tokenizer Iterator Index Builder then build the index from a STIA wrapped around a StreamTokenizer. I am having trouble implementing the hasNext and Next for my STIA, can anyone help me, here is my class: public class StreamTokenizerIteratorAdapter implements Iterator<Token> { DefaultIndexImpl index; StreamTokenizer source; public StreamTokenizerIteratorAdapter(final StreamTokenizer source) { if (source == null) throw new IllegalArgumentException("source == null"); } @Override public boolean hasNext() { return !index.isEmpty(); } public Token next() { if(!index.isEmpty()) return next(); else return null; } @Override public void remove() { throw new UnsupportedOperationException(); } } Should I be using the source element in the hasNext() and next()?

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  • Internal class and access to external members.

    - by Knowing me knowing you
    I have question with this same title here but now as I'll present in code below this seems to behave in the opposite way to the way explained to me in my first question with the same title. Ok code: class LINT_rep { private: char* my_data_; //stores separately every single digit from a number public: class Iterator:public iterator<bidirectional_operator_tag,char*> { Iterator(const LINT_rep&); }; }; #include "StdAfx.h" #include "LINT_rep.h" LINT_rep::Iterator::Iterator(const LINT_rep& owner):myData_(nullptr) { myData_ = owner.my_data_; /* HERE I'M ACCESSING my_data WHICH IS PRIVATE AND THIS CODE COMPILES ON VS2010 ULTIMATE BUT IT SHOULDN'T BECAUSE my_data IS PRIVATE AND OTHER CLASS SHOULDN'T HAVE ACCESS TO IT'S PRIVATE MEMB. AS EXPLAINED TO ME IN QUESTION TO WHICH I;VE PROVIDED LINK. */ } Question in the code. Thanks.

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  • enumerate all combinations in c++

    - by BCS
    My question is similar to this combinations question but in my case I have N (N 4) small sets (1-2 items per set for now might go to 3 maybe 4) and want to generate each combination of one item from each set. The current solution looks somethinging along the lines of this for(T:: iterator a = setA.begin(); a != setA.end(); ++a) for(T:: iterator b = setB.begin(); b != setB.end(); ++b) for(T:: iterator c = setC.begin(); c != setC.end(); ++c) for(T:: iterator d = setD.begin(); d != setD.end(); ++d) for(T:: iterator e = setE.begin(); e != setE.end(); ++e) something(*a,*b,*c,*d,*e); Simple, effective, probably reasonably efficient, but ugly and not very extensible. Does anyone know of a better/cleaner way to do this?

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  • More advanced usage of interfaces

    - by owca
    To be honest I'm not quite sure if I understand the task myself :) I was told to create class MySimpleIt, that implements Iterator and Iterable and will allow to run the provided test code. Arguments and variables of objects cannot be either Collections or arrays. The code : MySimpleIt msi=new MySimple(10,100, MySimpleIt.PRIME_NUMBERS); for(int el: msi) System.out.print(el+" "); System.out.println(); msi.setType(MySimpleIterator.ODD_NUMBERS); msi.setLimits(15,30); for(int el: msi) System.out.print(el+" "); System.out.println(); msi.setType(MySimpleIterator.EVEN_NUMBERS); for(int el: msi) System.out.print(el+" "); System.out.println(); The result I should obtain : 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 15 17 19 21 23 25 27 29 16 18 20 22 24 26 28 30 And here's my code : import java.util.Iterator; interface MySimpleIterator{ static int ODD_NUMBERS=0; static int EVEN_NUMBERS = 1; static int PRIME_NUMBERS = 2; int setType(int i); } public class MySimpleIt implements Iterable, Iterator, MySimpleIterator { public MySimple my; public MySimpleIt(MySimple m){ my = m; } public int setType(int i){ my.numbers = i; return my.numbers; } public void setLimits(int d, int u){ my.down = d; my.up = u; } public Iterator iterator(){ Iterator it = this.iterator(); return it; } public void remove(){ } public Object next(){ Object o = new Object(); return o; } public boolean hasNext(){ return true; } } class MySimple { public int down; public int up; public int numbers; public MySimple(int d, int u, int n){ down = d; up = u; numbers = n; } } In the test code I have error in line when creating MySimpleIt msi object, as it finds MySimple instead of MySimpleIt. Also I have errors in for-each loops, because compiler wants 'ints' there instead of Object. Anyone has any idea on how to solve it ?

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  • When to write an iterator?

    - by Jon
    I know this is probably a silly question.. When would I need to write my own iterator? Is it just when designing my own container class? Are there any other times when I would want to create my own iterator? Examples would be appropriated. -Jon

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  • How to read the whole istream correctly?

    - by L.Lawliet
    Here is a simple code to print all characters of a txt file on screen: #include <iostream> #include <fstream> #include <string> using namespace std; int main() { int **i; int j,k; char a; ifstream test("test.txt", ios::binary); while((a=test.get())!=-1)//if I use "while(!test.eof())" here, how to avoid the output of the last character(-1) to std::cout, or any ostream objects? { putchar(a);//also change this to putchar(test.get()); } getchar(); } As I noted in the code, if I use "test.eof()" to judge the end of test.txt, I'll always get an extra blank at the end of the output. How to avoid it?

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  • Correct way of setting a custom FileInfo class to an Iterator

    - by Gordon
    I am trying to set a custom class to an Iterator through the setInfoClass method: Use this method to set a custom class which will be used when getFileInfo and getPathInfo are called. The class name passed to this method must be derived from SplFileInfo. My class is like this (simplified example): class MyFileInfo extends SplFileInfo { public $props = array( 'foo' => '1', 'bar' => '2' ); } The iterator code is this: $rit = new RecursiveIteratorIterator( new RecursiveDirectoryIterator('/some/file/path/'), RecursiveIteratorIterator::SELF_FIRST); Since RecursiveDirectoryIterator is by inheritance through DirectoryIterator also an SplFileInfo object, it provides the setInfoClass method (it's not listed in the manual, but reflection shows it's there). Thus I can do: $rit->getInnerIterator()->setInfoClass('MyFileInfo'); All good up to here, but when iterating over the directory with foreach($rit as $file) { var_dump( $file ); } I get the following weird result object(MyFileInfo)#4 (3) { ["props"]=>UNKNOWN:0 ["pathName":"SplFileInfo":private]=>string(49) "/some/file/path/someFile.txt" ["fileName":"SplFileInfo":private]=>string(25) "someFile.txt" } So while MyFileInfo is picked up, I cannot access it's properties. If I add custom methods, I can invoke them fine, but any properties are UNKNOWN. If I don't set the info class to the iterator, but to the SplFileInfo object (like shown in the example in the manual), it will give the same UNKNOWN result: foreach($rit as $file) { // $file is a SplFileInfo instance $file->setInfoClass('MyFileInfo'); var_dump( $file->getFileInfo() ); } However, it will work when I do foreach($rit as $file) { $file = new MyFileInfo($file); var_dump( $file ); } Unfortunately, the code I a want to use this in is somewhat more complicated and stacks some more iterators. Creating the MyFileInfo class like this is not an option. So, does anyone know how to get this working or why PHP behaves this weird? Thanks.

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  • How to access valuestack objects within struts iterator?

    - by Monika Michael
    I have following code - <s:iterator value="reviews"> <img src="<s:property value="#request.restaurant.portalImage.url" />" /> <s:property value="user.firstName" /> <s:property value="user.lastName" /> <s:property value="rating" /> <s:property value="review" /> </s:iterator> reviews is a list of review objects which contain details of a review, such as rating and name of user. My problem is that i'm not able to access any of the objects present on the valuestack within the loop. Outside the loop <s:property value="#request.restaurant.portalImage.url" /> works correctly. But within the loop it prints null. AFAIK an iterator pushes it's collection on the valuestack so that all ognl expressions resolve against it. But I've used # which means I'm explicitly specifying the root object for resolution. Why is it still not working?

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  • Overloading operator>> for case insensitive string

    - by TheSOFan
    Given the definition of ci_string from cpp.reference.com, how would we go about implementing operator? My attempts at it involved std::read, but it doesn't seem to work (that is, gcount() properly counts the number of characters entered, but there is no output) #include <iostream> #include <cctype> #include <string> // ci_string definition goes here std::istream& operator>>(std::istream& in, ci_string& str) { return in.read(&*str.begin(), 4); } int main() { ci_string test_str; std::cin >> test_str; std::cout << test_str; return 0; }

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  • Cocoa NSStream works with SSL, with socks5, but not at the same time

    - by Evan D
    Upon connecting (to an FTP, at first without SSL) I run: NSArray *objects = [NSArray arrayWithObjects:@"proxy.ip", [NSNumber numberWithInt:1080], NSStreamSOCKSProxyVersion5, @"user", @"pass", nil]; NSArray *keys = [NSArray arrayWithObjects:NSStreamSOCKSProxyHostKey, NSStreamSOCKSProxyPortKey, NSStreamSOCKSProxyVersionKey, NSStreamSOCKSProxyUserKey, NSStreamSOCKSProxyPasswordKey, nil]; NSDictionary *proxyDictionary = [NSDictionary dictionaryWithObjects:objects forKeys:keys]; [iStream retain]; [iStream setDelegate:self]; [iStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [iStream setProperty:proxyDictionary forKey:NSStreamSOCKSProxyConfigurationKey]; [iStream open]; same for iStream. This allows me to connect succesfully through a socks5 proxy. If I continue without setProperty:proxyDictionary... (socks5 disabled) I would tell the server to switch to SSL, and then successfully apply these settings to the in/output streams, thus giving me a SSL connection: NSMutableDictionary *settings = [NSMutableDictionary dictionaryWithCapacity:1]; [settings setObject:(NSString *)NSStreamSocketSecurityLevelTLSv1 forKey:(NSString *)kCFStreamSSLLevel]; // to allow selfsigned certificates: [settings setObject:[NSNumber numberWithBool:YES] forKey:(NSString *)kCFStreamSSLAllowsAnyRoot]; [iStream retain]; [iStream setDelegate:self]; [iStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; CFReadStreamSetProperty((CFReadStreamRef)iStream, kCFStreamPropertySSLSettings, (CFTypeRef)settings); [iStream setProperty:NSStreamSocketSecurityLevelTLSv1 forKey:NSStreamSocketSecurityLevelKey]; same for oStream. All of which works fine if I disable socks5. If I turn it on (line 7 in the first snippit) I lose contact when applying the SSL settings. If I had to guess, I'd think it's losing some properties when applying (ssl) "settings"? Please help :) Evan

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  • Java - When to use Iterators?

    - by Walter White
    Hi all, I am trying to better understand when I should and should not use Iterators. To me, whenever I have a potentially large amount of data to iterate through, I write an Iterator for it. If it also lends itself to the Iterator interface, then it seems like a win. I was reading a little bit that there is a lot of overhead with using an Iterator. A good example of where I used an Iterator was to iterate through a bunch of SQL scripts to execute one query at a time, reading it in, then executing it. Is there another performance trade off I should be aware of? Before I used iterators, I would read the entire String of SQL commands to execute into an ArrayList, and the iterate through that. If the import is rather large (like for geolocation data, then the server tends to get bogged down). Walter

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  • How to iterate over modifed std::map values?

    - by Frank
    I have an std::map, and I would like to define an iterator that returns modified values. Typically, a std::map<int,double>::iterator iterates over std::pair<int,double>, and I would like the same behavior, just the double value is multiplied by a constant. I tried it with boost::transform_iterator, but it doesn't compile: #include <map> #include <boost/iterator/transform_iterator.hpp> #include <boost/functional.hpp> typedef std::map<int,double> Map; Map m; m[100] = 2.24; typedef boost::binder2nd< std::multiplies<double> > Function; typedef boost::transform_iterator<Function, Map::value_type*> MultiplyIter; MultiplyIter begin = boost::make_transform_iterator(m.begin(), Function(std::multiplies<double>(), 4)); // now want to similarly create an end iterator // and then iterate over the modified map The error is: error: conversion from 'boost ::transform_iterator< boost::binder2nd<multiplies<double> >, gen_map<int, double>::iterator , boost::use_default, boost::use_default >' to non-scalar type 'boost::transform_iterator< boost::binder2nd<multiplies<double> >, pair<const int, double> * , boost::use_default, boost::use_default >' requested What is gen_map and do I really need it? I adapted the transform_iterator tutorial code from here to write this code ...

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  • Java - Iterator: "Syntax error, parameterized types are only available if source level is 5.0"

    - by Helpme
    Hi! I'm purposely targeting Java OS 1.4.2 I'm trying to use an iterator combined with apache's POI to read an excel spreadsheet. The code runs perfectly in java 1.5, but in the 1.4.2 version I get the error listed in the question subject. the code is: Iterator myIter = null; it breaks on that line of code, which is clearly at the beginning of the application. I dont understand what needs to be done to correct this issue. Please let me know if you have any insight!

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  • Iterator for second to last element in a list

    - by BSchlinker
    I currently have the following for loop: for(list<string>::iterator jt=it->begin(); jt!=it->end()-1; jt++) I have a list of strings which is in a larger list (list<list<string> >). I want to loop through the contents of the innerlist until I get to the 2nd to last element. This is because I have already processed the contents of the final element, and have no reason to process them again. However, using it->end()-1 is invalid -- I cannot use the - operator here. While I could use the -- operator, this would decrement this final iterator on each cycle. I believe a STL list is a doubly linked list, so from my perspective, it should be possible to do this. Advice? Thanks in advance

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