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• Using string constants in implicit conversion

  - by kornelijepetak

  Consider the following code: public class TextType { public TextType(String text) { underlyingString = text; } public static implicit operator String(TextType text) { return text.underlyingString; } private String underlyingString; } TextType text = new TextType("Something"); String str = text; // This is OK. But I want to be able do the following, if possible. TextType textFromStringConstant = "SomeOtherText"; I can't extend the String class with the TextType implicit operator overload, but is there any way to assign a literal string to another class (which is handled by a method or something)? String is a reference type so when they developed C# they obviously had to use some way to get a string literal to the class. I just hope it's not hardcoded into the language.

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• C++, how implicit conversion/constructor are determined?

  - by aaa

  hello How does C++ determine implicit conversion/construction of objects few levels deep? for example: struct A; struct B: A {}; struct C { operator B(); } void f(A a); f(C()); Does it create tree of all possible conversions and chooses appropriate terminal? Something else? Thanks

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• Type classes or implicit parameters? What do you prefer and why? [closed]

  - by Petr Pudlák

  I was playing a bit with Scalaz and I realized that Haskell's type classes are very similar to Scala's implicit parameters. While Haskell passes the methods defined by a type class using hidden dictionaries, Scala allows a similar thing using implicit parameters. For example, in Haskell, one could write: incInside :: (Functor f) => f Int -> f Int incInside = fmap (+ 1) and the same function using Scalaz: import scalaz._; import Scalaz._; def incInside[F[_]](x: F[Int])(implicit fn: Functor[F]): F[Int] = fn.fmap(x, (_:Int) + 1); I wonder: If you could choose (i.e. your favorite language would offer both), what would you pick - implicits or type classes? And what are your pros/cons?

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• defining a simple implicit Arbitary

  - by FredOverflow

  I have a type Foo with a constructor that takes an Int. How do I define an implicit Arbitrary for Foo to be used with scalacheck? implicit def arbFoo: Arbitrary[Foo] = ??? I came up with the following solution, but it's a bit too "manual" and low-level for my taste: val fooGen = for (i <- Gen.choose(Int.MinValue, Int.MaxValue)) yield new Foo(i) implicit def arbFoo: Arbitrary[Foo] = Arbitrary(fooGen) Ideally, I would want a higher-order function where I just have to plug in an Int => Foo function. I managed to cut it down to: implicit def arbFoo = Arbitrary(Gen.resultOf((i: Int) => new Foo(i))) But I still feel like there has got to be a slightly simpler way.

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• Scala traits and implicit conversion confusion

  - by pr1001

  The following lines work when I enter them by hand on the Scala REPL (2.7.7): trait myTrait { override def toString = "something" } implicit def myTraitToString(input: myTrait): String = input.toString object myObject extends myTrait val s: String = myObject However, if I try to compile file with it I get the following error: [error] myTrait.scala:37: expected start of definition [error] implicit def myTraitToString(input: myTrait): String = input.toString [error] ^ Why? Thanks!

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• Can someone explain me implicit conversions in Scala?

  - by Oscar Reyes

  And more specifically how does the BigInt works for convert int to BigInt? In the source code it reads: ... implicit def int2bigInt(i: Int): BigInt = apply(i) ... How is this code invoked? I can understand how this other sample: "Date literals" works. In. val christmas = 24 Dec 2010 Defined by: implicit def dateLiterals(date: Int) = new { import java.util.Date def Dec(year: Int) = new Date(year, 11, date) } When int get's passed the message Dec with an int as parameter, the system looks for another method that can handle the request, in this case Dec(year:Int) Q1. Am I right in my understanding of Date literals? Q2. How does it apply to BigInt? Thanks

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• C# implicit conversions

  - by Chris Boden

  Hello, I'm currently working on an application where I need to load data from an SQL database and then assign the retrieved values into the properties of an object. I'm doing this by using reflection since the property names and column names are the same. However, many of the properties are using a custom struct type that is basically a currency wrapper for the decimal type. I have defined an implicit conversion in my struct: public static implicit operator Currency(decimal d) { return new Currency(d); } This works fine when I use it in code. However, when I have this: foreach (PropertyInfo p in props) { p.SetValue(this, table.Rows[0][p.Name], null); } It throws an ArgumentException stating that it cannot convert from System.Decimal to Currency. I'm confused since it works fine in any other circumstance.

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• Can someone exaplain me implicit parameters in Scala?

  - by Oscar Reyes

  And more specifically how does the BigInt works for convert int to BigInt? In the source code it reads: ... implicit def int2bigInt(i: Int): BigInt = apply(i) ... How is this code invoked? I can understand how this other sample: "Date literals" works. In. val christmas = 24 Dec 2010 Defined by: implicit def dateLiterals(date: Int) = new { import java.util.Date def Dec(year: Int) = new Date(year, 11, date) } When int get's passed the message Dec with an int as parameter, the system looks for another method that can handle the request, in this case Dec(year:Int) Q1. Am I right in my understanding of Date literals? Q2. How does it apply to BigInt? Thanks

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• Implicit array casting in C#

  - by Malki

  Hi, I have the following classes with an implicit cast operator defined: class A { ... } class B { private A m_a; public B(A a) { this.m_a = a; } public static implicit operator B(A a) { return new B(a); } } Now, I can implicitly cast A to B. But why can't I implicitly cast A[] to B[] ? static void Main(string[] args) { // compiles A a = new A(); B b = a; // doesn't compile A[] arrA = new A[] {new A(), new A()}; B[] arrB = arrA; } Thanks, Malki.

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• Question about implicit operator overloading in c#

  - by devoured elysium

  MyClass c = 10; Is there any way to make this code work? I know that through the implicit operator overloading you can get the opposite to work: int i = instanceOfMyClass; Thanks

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• Polymorphism, Autoboxing, and Implicit Conversions

  - by dbyrne

  Would you consider autoboxing in Java to be a form of polymorphism? Put another way, do you think autoboxing extends the polymorphic capabilities of Java? What about implicit conversions in Scala? My opinion is that they are both examples of polymorphism. Both features allow values of different data types to be handled in a uniform manner. My colleague disagrees with me. Who is right?

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• C#: Interfaces - Implicit and Explicit implementation

  - by Seb Nilsson

  What are the differences in implementing interfaces implicitly and explicitly in C#? When should you use implicit and when should you use explicit? Are there any pros and/or cons to one or the other?

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• Using implicit conversion as a substitute for multiple inheritance in .NET

  - by Daniel Plaisted

  I have a situation where I would like to have objects of a certain type be able to be used as two different types. If one of the "base" types was an interface this wouldn't be an issue, but in my case it is preferable that they both be concrete types. I am considering adding copies of the methods and properties of one of the base types to the derived type, and adding an implicit conversion from the derived type to that base type. Then users will be able treat the derived type as the base type by using the duplicated methods directly, by assigning it to a variable of the base type, or by passing it to a method that takes the base type. It seems like this solution will fit my needs well, but am I missing anything? Is there a situation where this won't work, or where it is likely to add confusion instead of simplicity when using the API?

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• MySQL 5.1 implicit cast from now() to a date field

  - by Savageman

  Hello, I have an issue with MySQL 5.1. A datetime data type isn't implicitly casted to match a date column. SELECT * FROM my_table WHERE my_date_field = NOW() This request doesn't return any rows using MySQL 5.1, but works well with version 5.0. If we use CURDATE() instead of NOW() it works both in MySQL 5.0 and MySQL 5.1. If the cast is explicit (CAST(NOW() AS DATE)), it also works both in MySQL 5.0 and MySQL 5.1. The problem only appears with implicit cast from datetime to date. Doesn't anyone already encountered this issue or has a clue about how to solve this problem? I know it's not the best to use NOW() instead of CURTIME(), but this isn't the question here. It is currently used in an application and the purpose is to avoid rewriting everything. Thanks!

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• Compiling a program with a legacy version of gcc

  - by wyatt

  This is probably a very difficult problem to troubleshoot with the information I can practically provide, but I'm hoping someone might be able to at least point me in a possible direction. I'm trying to install HTK (http://htk.eng.cam.ac.uk/), which, according to this page needs to be installed using gcc 3.4. Their method of implementing backwards compatibility: #yum install compat-gcc-34-c++ compat-gcc-34 won't work for me as I'm running Ubuntu (On that note, I take it I can't simply install YUM and the subsequent package, since it's an entirely different distro, but if I'm wrong I'd love to hear it). I instead installed two versions of gcc 3.4 - 3.4.0 and 3.4.6 using instructions from this site. I then added the lines suggested by that page to the top of the makefile (on this note, what's the difference between makefile and makefile.in? I tried adding the lines to the top of both files regardless), both for version 3.4.0 and 3.4.6, but both failed. I also tried, on the off-chance, compiling it with my current version (4.4.1), but that also failed. I got the errors: (cd HTKLib && make HTKLib.a) \ || case "" in k) fail=yes;; ) exit 1;; esac; make1: Entering directory /home/charles/bin/htk-3.4/HTKLib' gcc -ansi -D_SVID_SOURCE -DOSS_AUDIO -D'ARCH="i686"' -Wall -Wno-switch -g -O2 -I. -c -o HGraf.o HGraf.c HGraf.c:73:77: error: X11/Xlib.h: No such file or directory HGraf.c:74:23: error: X11/Xutil.h: No such file or directory HGraf.c:75:21: error: X11/Xos.h: No such file or directory HGraf.c:77:27: error: X11/keysymdef.h: No such file or directory HGraf.c:87: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘*’ token HGraf.c:88: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘rootW’ HGraf.c:91: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘theCmap’ HGraf.c:92: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘theGC’ HGraf.c:93: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘gcs’ HGraf.c:95: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘*’ token HGraf.c:96: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘report’ HGraf.c:97: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘hints’ HGraf.c:111: error: ‘GXcopy’ undeclared here (not in a function) HGraf.c:111: error: ‘GXor’ undeclared here (not in a function) HGraf.c:111: error: ‘GXxor’ undeclared here (not in a function) HGraf.c:111: error: ‘GXinvert’ undeclared here (not in a function) HGraf.c:151: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘*’ token HGraf.c: In function ‘InstallFonts’: HGraf.c:164: error: ‘FontInfo’ undeclared (first use in this function) HGraf.c:164: error: (Each undeclared identifier is reported only once HGraf.c:164: error: for each function it appears in.) HGraf.c:164: warning: implicit declaration of function ‘XLoadQueryFont’ HGraf.c:164: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:167: error: ‘DefaultFont’ undeclared (first use in this function) HGraf.c: At top level: HGraf.c:176: error: expected ‘)’ before ‘*’ token HGraf.c: In function ‘HGetEvent’: HGraf.c:219: error: ‘XEvent’ undeclared (first use in this function) HGraf.c:219: error: expected ‘;’ before ‘xev’ HGraf.c:223: warning: implicit declaration of function ‘XFlush’ HGraf.c:223: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:225: warning: implicit declaration of function ‘XEventsQueued’ HGraf.c:225: error: ‘QueuedAfterFlush’ undeclared (first use in this function) HGraf.c:226: warning: implicit declaration of function ‘XNextEvent’ HGraf.c:226: error: ‘xev’ undeclared (first use in this function) HGraf.c:228: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:230: error: ‘ButtonPress’ undeclared (first use in this function) HGraf.c:235: error: ‘ButtonRelease’ undeclared (first use in this function) HGraf.c:240: error: ‘MotionNotify’ undeclared (first use in this function) HGraf.c:245: error: ‘KeyPress’ undeclared (first use in this function) HGraf.c:249: warning: implicit declaration of function ‘DecodeKeyPress’ HGraf.c:251: error: ‘KeyRelease’ undeclared (first use in this function) HGraf.c:257: error: ‘Expose’ undeclared (first use in this function) HGraf.c: In function ‘HEventsPending’: HGraf.c:281: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:281: error: ‘QueuedAfterFlush’ undeclared (first use in this function) HGraf.c: In function ‘HMousePos’: HGraf.c:288: error: ‘Window’ undeclared (first use in this function) HGraf.c:288: error: expected ‘;’ before ‘root’ HGraf.c:293: warning: implicit declaration of function ‘XQueryPointer’ HGraf.c:293: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:293: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:293: error: ‘root’ undeclared (first use in this function) HGraf.c:293: error: ‘child’ undeclared (first use in this function) HGraf.c: In function ‘InstallColours’: HGraf.c:311: error: ‘XColor’ undeclared (first use in this function) HGraf.c:311: error: expected ‘;’ before ‘greyDef’ HGraf.c:317: warning: implicit declaration of function ‘XParseColor’ HGraf.c:317: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:317: error: ‘theCmap’ undeclared (first use in this function) HGraf.c:317: error: ‘colourDef’ undeclared (first use in this function) HGraf.c:320: warning: implicit declaration of function ‘XAllocColor’ HGraf.c:334: error: ‘whiteDef’ undeclared (first use in this function) HGraf.c:334: warning: implicit declaration of function ‘XQueryColor’ HGraf.c:335: error: ‘blackDef’ undeclared (first use in this function) HGraf.c:341: error: ‘greyDef’ undeclared (first use in this function) HGraf.c: In function ‘HSetColour’: HGraf.c:361: warning: implicit declaration of function ‘XSetForeground’ HGraf.c:361: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:361: error: ‘gcs’ undeclared (first use in this function) HGraf.c: In function ‘HSetGrey’: HGraf.c:370: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:370: error: ‘gcs’ undeclared (first use in this function) HGraf.c: In function ‘HDrawLines’: HGraf.c:388: warning: implicit declaration of function ‘XDrawLines’ HGraf.c:388: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:388: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:388: error: ‘theGC’ undeclared (first use in this function) HGraf.c:388: error: ‘XPoint’ undeclared (first use in this function) HGraf.c:388: error: expected expression before ‘)’ token HGraf.c: In function ‘HDrawRectangle’: HGraf.c:395: warning: implicit declaration of function ‘XDrawRectangle’ HGraf.c:395: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:395: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:395: error: ‘theGC’ undeclared (first use in this function) HGraf.c: In function ‘HFillRectangle’: HGraf.c:402: warning: implicit declaration of function ‘XFillRectangle’ HGraf.c:402: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:402: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:402: error: ‘theGC’ undeclared (first use in this function) HGraf.c: In function ‘HDrawLine’: HGraf.c:408: warning: implicit declaration of function ‘XDrawLine’ HGraf.c:408: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:408: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:408: error: ‘theGC’ undeclared (first use in this function) HGraf.c: In function ‘HFillPolygon’: HGraf.c:414: warning: implicit declaration of function ‘XFillPolygon’ HGraf.c:414: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:414: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:414: error: ‘theGC’ undeclared (first use in this function) HGraf.c:414: error: ‘XPoint’ undeclared (first use in this function) HGraf.c:414: error: expected expression before ‘)’ token HGraf.c: In function ‘HDrawArc’: HGraf.c:427: warning: implicit declaration of function ‘XDrawArc’ HGraf.c:427: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:427: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:427: error: ‘theGC’ undeclared (first use in this function) HGraf.c: In function ‘HFillArc’: HGraf.c:440: warning: implicit declaration of function ‘XFillArc’ HGraf.c:440: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:440: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:440: error: ‘theGC’ undeclared (first use in this function) HGraf.c: In function ‘HPrintf’: HGraf.c:451: warning: implicit declaration of function ‘XDrawString’ HGraf.c:451: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:451: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:451: error: ‘theGC’ undeclared (first use in this function) HGraf.c: In function ‘HCopyArea’: HGraf.c:457: warning: implicit declaration of function ‘XCopyArea’ HGraf.c:457: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:457: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:457: error: ‘theGC’ undeclared (first use in this function) HGraf.c: In function ‘HPlotVector’: HGraf.c:476: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:476: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:476: error: ‘theGC’ undeclared (first use in this function) HGraf.c: In function ‘HSetFontSize’: HGraf.c:490: error: ‘CurrentFont’ undeclared (first use in this function) HGraf.c:490: error: ‘DefaultFont’ undeclared (first use in this function) HGraf.c:499: error: ‘FontInfo’ undeclared (first use in this function) HGraf.c:502: warning: implicit declaration of function ‘XSetFont’ HGraf.c:502: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:502: error: ‘gcs’ undeclared (first use in this function) HGraf.c: In function ‘HSetLineWidth’: HGraf.c:511: warning: implicit declaration of function ‘XSetLineAttributes’ HGraf.c:511: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:511: error: ‘gcs’ undeclared (first use in this function) HGraf.c:511: error: ‘LineSolid’ undeclared (first use in this function) HGraf.c:511: error: ‘JoinRound’ undeclared (first use in this function) HGraf.c:511: error: ‘FillSolid’ undeclared (first use in this function) HGraf.c: In function ‘HSetXMode’: HGraf.c:517: error: ‘theGC’ undeclared (first use in this function) HGraf.c:517: error: ‘gcs’ undeclared (first use in this function) HGraf.c: In function ‘CentreX’: HGraf.c:523: warning: implicit declaration of function ‘XTextWidth’ HGraf.c:523: error: ‘CurrentFont’ undeclared (first use in this function) HGraf.c: In function ‘CentreY’: HGraf.c:529: error: ‘CurrentFont’ undeclared (first use in this function) HGraf.c: In function ‘HTextWidth’: HGraf.c:535: error: ‘CurrentFont’ undeclared (first use in this function) HGraf.c: In function ‘HTextHeight’: HGraf.c:541: error: ‘CurrentFont’ undeclared (first use in this function) HGraf.c: In function ‘HDrawImage’: HGraf.c:550: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘*’ token HGraf.c:550: error: ‘xi’ undeclared (first use in this function) HGraf.c:557: warning: implicit declaration of function ‘XDestroyImage’ HGraf.c:558: warning: implicit declaration of function ‘XGetImage’ HGraf.c:558: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:558: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:558: error: ‘AllPlanes’ undeclared (first use in this function) HGraf.c:558: error: ‘XYPixmap’ undeclared (first use in this function) HGraf.c:562: warning: implicit declaration of function ‘XPutPixel’ HGraf.c:564: warning: implicit declaration of function ‘XPutImage’ HGraf.c:564: error: ‘theGC’ undeclared (first use in this function) HGraf.c: In function ‘HFlush’: HGraf.c:570: error: ‘theDisp’ undeclared (first use in this function) HGraf.c: In function ‘InitGCs’: HGraf.c:780: error: ‘XGCValues’ undeclared (first use in this function) HGraf.c:780: error: expected ‘;’ before ‘values’ HGraf.c:783: error: ‘GCLineWidth’ undeclared (first use in this function) HGraf.c:783: error: ‘GCFunction’ undeclared (first use in this function) HGraf.c:783: error: ‘GCForeground’ undeclared (first use in this function) HGraf.c:785: error: ‘values’ undeclared (first use in this function) HGraf.c:788: error: ‘gcs’ undeclared (first use in this function) HGraf.c:788: warning: implicit declaration of function ‘XCreateGC’ HGraf.c:788: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:788: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:790: error: ‘GCPlaneMask’ undeclared (first use in this function) HGraf.c: In function ‘InitGlobals’: HGraf.c:800: warning: implicit declaration of function ‘DefaultScreen’ HGraf.c:800: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:801: error: ‘theCmap’ undeclared (first use in this function) HGraf.c:801: warning: implicit declaration of function ‘DefaultColormap’ HGraf.c:802: error: ‘rootW’ undeclared (first use in this function) HGraf.c:802: warning: implicit declaration of function ‘RootWindow’ HGraf.c:803: error: ‘theGC’ undeclared (first use in this function) HGraf.c:803: warning: implicit declaration of function ‘DefaultGC’ HGraf.c:804: error: ‘theVisual’ undeclared (first use in this function) HGraf.c:804: warning: implicit declaration of function ‘DefaultVisual’ HGraf.c:805: warning: implicit declaration of function ‘DisplayCells’ HGraf.c:806: warning: implicit declaration of function ‘DisplayWidth’ HGraf.c:807: warning: implicit declaration of function ‘DisplayHeight’ HGraf.c:808: warning: implicit declaration of function ‘DisplayPlanes’ HGraf.c:809: warning: implicit declaration of function ‘WhitePixel’ HGraf.c:810: warning: implicit declaration of function ‘BlackPixel’ HGraf.c: In function ‘MakeXGraf’: HGraf.c:817: error: ‘Window’ undeclared (first use in this function) HGraf.c:817: error: expected ‘;’ before ‘window’ HGraf.c:818: error: ‘XSetWindowAttributes’ undeclared (first use in this function) HGraf.c:818: error: expected ‘;’ before ‘setwinattr’ HGraf.c:823: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:823: warning: implicit declaration of function ‘XOpenDisplay’ HGraf.c:824: warning: implicit declaration of function ‘XDisplayName’ HGraf.c:828: error: ‘parent’ undeclared (first use in this function) HGraf.c:829: error: ‘window’ undeclared (first use in this function) HGraf.c:829: warning: implicit declaration of function ‘XCreateSimpleWindow’ HGraf.c:831: error: ‘CWBackingStore’ undeclared (first use in this function) HGraf.c:831: error: ‘setwinattr’ undeclared (first use in this function) HGraf.c:831: error: ‘WhenMapped’ undeclared (first use in this function) HGraf.c:832: warning: implicit declaration of function ‘XChangeWindowAttributes’ HGraf.c:834: error: ‘hints’ undeclared (first use in this function) HGraf.c:834: error: ‘PPosition’ undeclared (first use in this function) HGraf.c:834: error: ‘PSize’ undeclared (first use in this function) HGraf.c:834: error: ‘PMaxSize’ undeclared (first use in this function) HGraf.c:834: error: ‘PMinSize’ undeclared (first use in this function) HGraf.c:841: warning: implicit declaration of function ‘XSetStandardProperties’ HGraf.c:841: error: ‘None’ undeclared (first use in this function) HGraf.c:843: warning: implicit declaration of function ‘XSelectInput’ HGraf.c:843: error: ‘ExposureMask’ undeclared (first use in this function) HGraf.c:843: error: ‘KeyPressMask’ undeclared (first use in this function) HGraf.c:843: error: ‘ButtonPressMask’ undeclared (first use in this function) HGraf.c:844: error: ‘ButtonReleaseMask’ undeclared (first use in this function) HGraf.c:844: error: ‘PointerMotionHintMask’ undeclared (first use in this function) HGraf.c:844: error: ‘PointerMotionMask’ undeclared (first use in this function) HGraf.c:845: warning: implicit declaration of function ‘XMapWindow’ HGraf.c:845: error: ‘theWindow’ undeclared (first use in this function) HGraf.c:850: error: ‘report’ undeclared (first use in this function) HGraf.c:851: error: ‘Expose’ undeclared (first use in this function) HGraf.c:852: warning: implicit declaration of function ‘XSendEvent’ HGraf.c:852: error: ‘False’ undeclared (first use in this function) HGraf.c: In function ‘TermHGraf’: HGraf.c:861: error: ‘theDisp’ undeclared (first use in this function) HGraf.c:862: warning: implicit declaration of function ‘XCloseDisplay’ make[1]: *** [HGraf.o] Error 1 make[1]: Leaving directory/home/charles/bin/htk-3.4/HTKLib' make: ** [HTKLib/HTKLib.a] Error 1 Thank you for any help you can provide.

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• Explicit behavior with checks vs. implicit behavior

  - by Silviu

  I'm not sure how to construct the question but I'm interested to know what do you guys think of the following situations and which one would you prefer. We're working at a client-server application with winforms. And we have a control that has some fields automatically calculated upon filling another field. So we're having a field currency which when filled by the user would determine an automatic filling of another field, maybe more fields. When the user fills the currency field, a Currency object would be retrieved from a cache based on the string introduced by the user. If entered currency is not found in the cache a null reference is returned by the cache object. Further down when asking the application layer to compute the other fields based on the currency, given a null currency a null specific field would be returned. This way the default, implicit behavior is to clear all fields. Which is the expected behavior. What i would call the explicit implementation would be to verify that the Currency object is null in which case the depending fields are cleared explicitly. I think that the latter version is more clear, less error prone and more testable. But it implies a form of redundancy. The former version is not as clear and it implies a certain behavior from the application layer which is not expressed in the tests. Maybe in the lower layer tests but when the need arises to modify the lower layers, so that given a null currency something else should be returned, i don't think a test that says just that without a motivation is going to be an impediment for introducing a bug in upper layers. What do you guys think?

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• MAMP + Python MySQLDB - trouble installing

  - by Frederico

  I'm currently running the latest version of MAMP on my Snow Leopard OSX, and I'm trying to install MySQLDB. Downloaded: MySQL-python-1.2.3c1 I went into the setup_posix.py and adjusted the location of the mysql_config to the one in MAMP: mysql_config.path = "/Applications/MAMP/Library/bin/mysql_config" When trying to build I get the error below. Could anyone give me a hand please: creating build/temp.macosx-10.6-universal-2.6 gcc-4.2 -fno-strict-aliasing -fno-common -dynamic -DNDEBUG -g -fwrapv -Os -Wall -Wstrict-prototypes -DENABLE_DTRACE -arch i386 -arch ppc -arch x86_64 -pipe -Dversion_info=(1,2,3,'gamma',1) -D_version_=1.2.3c1 -I/Applications/MAMP/Library/include/mysql -I/System/Library/Frameworks/Python.framework/Versions/2.6/include/python2.6 -c _mysql.c -o build/temp.macosx-10.6-universal-2.6/_mysql.o -fno-omit-frame-pointer -D_P1003_1B_VISIBLE -DSIGNAL_WITH_VIO_CLOSE -DSIGNALS_DONT_BREAK_READ -DIGNORE_SIGHUP_SIGQUIT -DDONT_DECLARE_CXA_PURE_VIRTUAL _mysql.c:36:23: error: my_config.h: No such file or directory _mysql.c:38:19: error: mysql.h: No such file or directory _mysql.c:39:26: error: mysqld_error.h: No such file or directory _mysql.c:40:20: error: errmsg.h: No such file or directory _mysql.c:76: error: expected specifier-qualifier-list before ‘MYSQL’ _mysql.c:90: error: expected specifier-qualifier-list before ‘MYSQL_RES’ _mysql.c: In function ‘_mysql_Exception’: _mysql.c:120: warning: implicit declaration of function ‘mysql_errno’ _mysql.c:120: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:123: error: ‘CR_MAX_ERROR’ undeclared (first use in this function) _mysql.c:123: error: (Each undeclared identifier is reported only once _mysql.c:123: error: for each function it appears in.) _mysql.c:131: error: ‘CR_COMMANDS_OUT_OF_SYNC’ undeclared (first use in this function) _mysql.c:132: error: ‘ER_DB_CREATE_EXISTS’ undeclared (first use in this function) _mysql.c:133: error: ‘ER_SYNTAX_ERROR’ undeclared (first use in this function) _mysql.c:134: error: ‘ER_PARSE_ERROR’ undeclared (first use in this function) _mysql.c:135: error: ‘ER_NO_SUCH_TABLE’ undeclared (first use in this function) _mysql.c:136: error: ‘ER_WRONG_DB_NAME’ undeclared (first use in this function) _mysql.c:137: error: ‘ER_WRONG_TABLE_NAME’ undeclared (first use in this function) _mysql.c:138: error: ‘ER_FIELD_SPECIFIED_TWICE’ undeclared (first use in this function) _mysql.c:139: error: ‘ER_INVALID_GROUP_FUNC_USE’ undeclared (first use in this function) _mysql.c:140: error: ‘ER_UNSUPPORTED_EXTENSION’ undeclared (first use in this function) _mysql.c:141: error: ‘ER_TABLE_MUST_HAVE_COLUMNS’ undeclared (first use in this function) _mysql.c:170: error: ‘ER_DUP_ENTRY’ undeclared (first use in this function) _mysql.c:213: warning: implicit declaration of function ‘mysql_error’ _mysql.c:213: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:213: warning: passing argument 1 of ‘PyString_FromString’ makes pointer from integer without a cast _mysql.c: In function ‘_mysql_server_init’: _mysql.c:308: warning: label ‘finish’ defined but not used _mysql.c:234: warning: unused variable ‘item’ _mysql.c:233: warning: unused variable ‘groupc’ _mysql.c:233: warning: unused variable ‘i’ _mysql.c:233: warning: unused variable ‘cmd_argc’ _mysql.c:232: warning: unused variable ‘s’ _mysql.c: In function ‘_mysql_ResultObject_Initialize’: _mysql.c:363: error: ‘MYSQL_RES’ undeclared (first use in this function) _mysql.c:363: error: ‘result’ undeclared (first use in this function) _mysql.c:368: error: ‘MYSQL_FIELD’ undeclared (first use in this function) _mysql.c:368: error: ‘fields’ undeclared (first use in this function) _mysql.c:377: error: ‘_mysql_ResultObject’ has no member named ‘use’ _mysql.c:380: warning: implicit declaration of function ‘mysql_use_result’ _mysql.c:380: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:382: warning: implicit declaration of function ‘mysql_store_result’ _mysql.c:382: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:383: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:386: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:389: warning: implicit declaration of function ‘mysql_num_fields’ _mysql.c:390: error: ‘_mysql_ResultObject’ has no member named ‘nfields’ _mysql.c:391: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:392: warning: implicit declaration of function ‘mysql_fetch_fields’ _mysql.c:438: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c: In function ‘_mysql_ResultObject_traverse’: _mysql.c:450: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:451: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c: In function ‘_mysql_ResultObject_clear’: _mysql.c:462: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:462: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:462: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:462: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:463: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c: In function ‘_mysql_ConnectionObject_Initialize’: _mysql.c:475: error: ‘MYSQL’ undeclared (first use in this function) _mysql.c:475: error: ‘conn’ undeclared (first use in this function) _mysql.c:500: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c:501: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:525: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c:547: warning: implicit declaration of function ‘mysql_init’ _mysql.c:547: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:550: warning: implicit declaration of function ‘mysql_options’ _mysql.c:550: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:550: error: ‘MYSQL_OPT_CONNECT_TIMEOUT’ undeclared (first use in this function) _mysql.c:554: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:554: error: ‘MYSQL_OPT_COMPRESS’ undeclared (first use in this function) _mysql.c:555: error: ‘CLIENT_COMPRESS’ undeclared (first use in this function) _mysql.c:558: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:558: error: ‘MYSQL_OPT_NAMED_PIPE’ undeclared (first use in this function) _mysql.c:560: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:560: error: ‘MYSQL_INIT_COMMAND’ undeclared (first use in this function) _mysql.c:562: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:562: error: ‘MYSQL_READ_DEFAULT_FILE’ undeclared (first use in this function) _mysql.c:564: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:564: error: ‘MYSQL_READ_DEFAULT_GROUP’ undeclared (first use in this function) _mysql.c:567: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:567: error: ‘MYSQL_OPT_LOCAL_INFILE’ undeclared (first use in this function) _mysql.c:575: warning: implicit declaration of function ‘mysql_real_connect’ _mysql.c:575: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:590: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c: In function ‘_mysql_ConnectionObject_traverse’: _mysql.c:671: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c:672: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c: In function ‘_mysql_ConnectionObject_clear’: _mysql.c:680: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c:680: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c:680: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c:680: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c:681: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c: In function ‘_mysql_ConnectionObject_close’: _mysql.c:696: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:698: warning: implicit declaration of function ‘mysql_close’ _mysql.c:698: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:700: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c: In function ‘_mysql_ConnectionObject_affected_rows’: _mysql.c:722: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:723: warning: implicit declaration of function ‘mysql_affected_rows’ _mysql.c:723: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_debug’: _mysql.c:739: warning: implicit declaration of function ‘mysql_debug’ _mysql.c: In function ‘_mysql_ConnectionObject_dump_debug_info’: _mysql.c:757: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:759: warning: implicit declaration of function ‘mysql_dump_debug_info’ _mysql.c:759: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ConnectionObject_autocommit’: _mysql.c:783: warning: implicit declaration of function ‘mysql_query’ _mysql.c:783: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ConnectionObject_commit’: _mysql.c:806: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ConnectionObject_rollback’: _mysql.c:828: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ConnectionObject_errno’: _mysql.c:940: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:941: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ConnectionObject_error’: _mysql.c:956: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:957: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:957: warning: passing argument 1 of ‘PyString_FromString’ makes pointer from integer without a cast _mysql.c: In function ‘_mysql_escape_string’: _mysql.c:981: warning: implicit declaration of function ‘mysql_escape_string’ _mysql.c: In function ‘_mysql_escape’: _mysql.c:1088: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c: In function ‘_mysql_ResultObject_describe’: _mysql.c:1168: error: ‘MYSQL_FIELD’ undeclared (first use in this function) _mysql.c:1168: error: ‘fields’ undeclared (first use in this function) _mysql.c:1171: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1172: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:1173: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:1184: warning: implicit declaration of function ‘IS_NOT_NULL’ _mysql.c: In function ‘_mysql_ResultObject_field_flags’: _mysql.c:1204: error: ‘MYSQL_FIELD’ undeclared (first use in this function) _mysql.c:1204: error: ‘fields’ undeclared (first use in this function) _mysql.c:1207: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1208: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:1209: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c: At top level: _mysql.c:1250: error: expected declaration specifiers or ‘...’ before ‘MYSQL_ROW’ _mysql.c: In function ‘_mysql_row_to_tuple’: _mysql.c:1256: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:1258: warning: implicit declaration of function ‘mysql_fetch_lengths’ _mysql.c:1258: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:1258: warning: assignment makes pointer from integer without a cast _mysql.c:1261: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:1262: error: ‘row’ undeclared (first use in this function) _mysql.c: At top level: _mysql.c:1275: error: expected declaration specifiers or ‘...’ before ‘MYSQL_ROW’ _mysql.c: In function ‘_mysql_row_to_dict’: _mysql.c:1280: error: ‘MYSQL_FIELD’ undeclared (first use in this function) _mysql.c:1280: error: ‘fields’ undeclared (first use in this function) _mysql.c:1282: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:1284: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:1284: warning: assignment makes pointer from integer without a cast _mysql.c:1285: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:1288: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:1289: error: ‘row’ undeclared (first use in this function) _mysql.c: At top level: _mysql.c:1314: error: expected declaration specifiers or ‘...’ before ‘MYSQL_ROW’ _mysql.c: In function ‘_mysql_row_to_dict_old’: _mysql.c:1319: error: ‘MYSQL_FIELD’ undeclared (first use in this function) _mysql.c:1319: error: ‘fields’ undeclared (first use in this function) _mysql.c:1321: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:1323: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:1323: warning: assignment makes pointer from integer without a cast _mysql.c:1324: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:1327: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:1328: error: ‘row’ undeclared (first use in this function) _mysql.c: At top level: _mysql.c:1350: error: expected declaration specifiers or ‘...’ before ‘MYSQL_ROW’ _mysql.c: In function ‘mysql_fetch_row’: _mysql.c:1361: error: ‘MYSQL_ROW’ undeclared (first use in this function) _mysql.c:1361: error: expected ‘;’ before ‘row’ _mysql.c:1365: error: ‘_mysql_ResultObject’ has no member named ‘use’ _mysql.c:1366: error: ‘row’ undeclared (first use in this function) _mysql.c:1366: warning: implicit declaration of function ‘mysql_fetch_row’ _mysql.c:1366: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:1369: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:1372: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:1380: error: too many arguments to function ‘convert_row’ _mysql.c: In function ‘_mysql_ResultObject_fetch_row’: _mysql.c:1404: error: expected declaration specifiers or ‘...’ before ‘MYSQL_ROW’ _mysql.c:1419: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1431: error: ‘_mysql_ResultObject’ has no member named ‘use’ _mysql.c:1445: warning: implicit declaration of function ‘mysql_num_rows’ _mysql.c:1445: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c: In function ‘_mysql_ConnectionObject_character_set_name’: _mysql.c:1512: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c: In function ‘_mysql_get_client_info’: _mysql.c:1603: warning: implicit declaration of function ‘mysql_get_client_info’ _mysql.c:1603: warning: passing argument 1 of ‘PyString_FromString’ makes pointer from integer without a cast _mysql.c: In function ‘_mysql_ConnectionObject_get_host_info’: _mysql.c:1617: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1618: warning: implicit declaration of function ‘mysql_get_host_info’ _mysql.c:1618: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:1618: warning: passing argument 1 of ‘PyString_FromString’ makes pointer from integer without a cast _mysql.c: In function ‘_mysql_ConnectionObject_get_proto_info’: _mysql.c:1632: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1633: warning: implicit declaration of function ‘mysql_get_proto_info’ _mysql.c:1633: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ConnectionObject_get_server_info’: _mysql.c:1647: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1648: warning: implicit declaration of function ‘mysql_get_server_info’ _mysql.c:1648: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:1648: warning: passing argument 1 of ‘PyString_FromString’ makes pointer from integer without a cast _mysql.c: In function ‘_mysql_ConnectionObject_info’: _mysql.c:1664: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1665: warning: implicit declaration of function ‘mysql_info’ _mysql.c:1665: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:1665: warning: assignment makes pointer from integer without a cast _mysql.c: In function ‘_mysql_ConnectionObject_insert_id’: _mysql.c:1697: error: ‘my_ulonglong’ undeclared (first use in this function) _mysql.c:1697: error: expected ‘;’ before ‘r’ _mysql.c:1699: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1701: error: ‘r’ undeclared (first use in this function) _mysql.c:1701: warning: implicit declaration of function ‘mysql_insert_id’ _mysql.c:1701: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ConnectionObject_kill’: _mysql.c:1718: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1720: warning: implicit declaration of function ‘mysql_kill’ _mysql.c:1720: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ConnectionObject_field_count’: _mysql.c:1739: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1741: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ResultObject_num_fields’: _mysql.c:1756: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1757: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c: In function ‘_mysql_ResultObject_num_rows’: _mysql.c:1772: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1773: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c: In function ‘_mysql_ConnectionObject_ping’: _mysql.c:1802: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1803: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:1805: warning: implicit declaration of function ‘mysql_ping’ _mysql.c:1805: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ConnectionObject_query’: _mysql.c:1826: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1828: warning: implicit declaration of function ‘mysql_real_query’ _mysql.c:1828: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ConnectionObject_select_db’: _mysql.c:1856: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1858: warning: implicit declaration of function ‘mysql_select_db’ _mysql.c:1858: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ConnectionObject_shutdown’: _mysql.c:1877: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1879: warning: implicit declaration of function ‘mysql_shutdown’ _mysql.c:1879: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ConnectionObject_stat’: _mysql.c:1904: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1906: warning: implicit declaration of function ‘mysql_stat’ _mysql.c:1906: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:1906: warning: assignment makes pointer from integer without a cast _mysql.c: In function ‘_mysql_ConnectionObject_store_result’: _mysql.c:1927: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1928: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c:1937: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c: In function ‘_mysql_ConnectionObject_thread_id’: _mysql.c:1966: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1968: warning: implicit declaration of function ‘mysql_thread_id’ _mysql.c:1968: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ConnectionObject_use_result’: _mysql.c:1988: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:1989: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c:1998: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c: In function ‘_mysql_ConnectionObject_dealloc’: _mysql.c:2016: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c: In function ‘_mysql_ConnectionObject_repr’: _mysql.c:2028: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:2029: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c: In function ‘_mysql_ResultObject_data_seek’: _mysql.c:2047: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:2048: warning: implicit declaration of function ‘mysql_data_seek’ _mysql.c:2048: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c: In function ‘_mysql_ResultObject_row_seek’: _mysql.c:2061: error: ‘MYSQL_ROW_OFFSET’ undeclared (first use in this function) _mysql.c:2061: error: expected ‘;’ before ‘r’ _mysql.c:2063: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:2064: error: ‘_mysql_ResultObject’ has no member named ‘use’ _mysql.c:2069: error: ‘r’ undeclared (first use in this function) _mysql.c:2069: warning: implicit declaration of function ‘mysql_row_tell’ _mysql.c:2069: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:2070: warning: implicit declaration of function ‘mysql_row_seek’ _mysql.c:2070: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c: In function ‘_mysql_ResultObject_row_tell’: _mysql.c:2082: error: ‘MYSQL_ROW_OFFSET’ undeclared (first use in this function) _mysql.c:2082: error: expected ‘;’ before ‘r’ _mysql.c:2084: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:2085: error: ‘_mysql_ResultObject’ has no member named ‘use’ _mysql.c:2090: error: ‘r’ undeclared (first use in this function) _mysql.c:2090: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:2091: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c: In function ‘_mysql_ResultObject_dealloc’: _mysql.c:2099: warning: implicit declaration of function ‘mysql_free_result’ _mysql.c:2099: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c: At top level: _mysql.c:2330: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:2337: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c:2344: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:2351: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:2358: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:2421: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:2421: error: initializer element is not constant _mysql.c:2421: error: (near initialization for ‘_mysql_ResultObject_memberlist[0].offset’) _mysql.c: In function ‘_mysql_ConnectionObject_getattr’: _mysql.c:2443: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:36:23: error: my_config.h: No such file or directory _mysql.c:38:19: error: mysql.h: No such file or directory _mysql.c:39:26: error: mysqld_error.h: No such file or directory _mysql.c:40:20: error: errmsg.h: No such file or directory _mysql.c:76: error: expected specifier-qualifier-list before ‘MYSQL’ _mysql.c:90: error: expected specifier-qualifier-list before ‘MYSQL_RES’ _mysql.c: In function ‘_mysql_Exception’: _mysql.c:120: warning: implicit declaration of function ‘mysql_errno’ _mysql.c:120: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:123: error: ‘CR_MAX_ERROR’ undeclared (first use in this function) _mysql.c:123: error: (Each undeclared identifier is reported only once _mysql.c:123: error: for each function it appears in.) _mysql.c:131: error: ‘CR_COMMANDS_OUT_OF_SYNC’ undeclared (first use in this function) _mysql.c:132: error: ‘ER_DB_CREATE_EXISTS’ undeclared (first use in this function) _mysql.c:133: error: ‘ER_SYNTAX_ERROR’ undeclared (first use in this function) _mysql.c:134: error: ‘ER_PARSE_ERROR’ undeclared (first use in this function) _mysql.c:135: error: ‘ER_NO_SUCH_TABLE’ undeclared (first use in this function) _mysql.c:136: error: ‘ER_WRONG_DB_NAME’ undeclared (first use in this function) _mysql.c:137: error: ‘ER_WRONG_TABLE_NAME’ undeclared (first use in this function) _mysql.c:138: error: ‘ER_FIELD_SPECIFIED_TWICE’ undeclared (first use in this function) _mysql.c:139: error: ‘ER_INVALID_GROUP_FUNC_USE’ undeclared (first use in this function) _mysql.c:140: error: ‘ER_UNSUPPORTED_EXTENSION’ undeclared (first use in this function) _mysql.c:141: error: ‘ER_TABLE_MUST_HAVE_COLUMNS’ undeclared (first use in this function) _mysql.c:170: error: ‘ER_DUP_ENTRY’ undeclared (first use in this function) _mysql.c:213: warning: implicit declaration of function ‘mysql_error’ _mysql.c:213: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:213: warning: passing argument 1 of ‘PyString_FromString’ makes pointer from integer without a cast _mysql.c: In function ‘_mysql_server_init’: _mysql.c:308: warning: label ‘finish’ defined but not used _mysql.c:234: warning: unused variable ‘item’ _mysql.c:233: warning: unused variable ‘groupc’ _mysql.c:233: warning: unused variable ‘i’ _mysql.c:233: warning: unused variable ‘cmd_argc’ _mysql.c:232: warning: unused variable ‘s’ _mysql.c: In function ‘_mysql_ResultObject_Initialize’: _mysql.c:363: error: ‘MYSQL_RES’ undeclared (first use in this function) _mysql.c:363: error: ‘result’ undeclared (first use in this function) _mysql.c:368: error: ‘MYSQL_FIELD’ undeclared (first use in this function) _mysql.c:368: error: ‘fields’ undeclared (first use in this function) _mysql.c:377: error: ‘_mysql_ResultObject’ has no member named ‘use’ _mysql.c:380: warning: implicit declaration of function ‘mysql_use_result’ _mysql.c:380: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:382: warning: implicit declaration of function ‘mysql_store_result’ _mysql.c:382: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:383: error: ‘_mysql_ResultObject’ has no member named ‘result’ _mysql.c:386: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:389: warning: implicit declaration of function ‘mysql_num_fields’ _mysql.c:390: error: ‘_mysql_ResultObject’ has no member named ‘nfields’ _mysql.c:391: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:392: warning: implicit declaration of function ‘mysql_fetch_fields’ _mysql.c:438: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c: In function ‘_mysql_ResultObject_traverse’: _mysql.c:450: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:451: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c: In function ‘_mysql_ResultObject_clear’: _mysql.c:462: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:462: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:462: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:462: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c:463: error: ‘_mysql_ResultObject’ has no member named ‘converter’ _mysql.c: In function ‘_mysql_ConnectionObject_Initialize’: _mysql.c:475: error: ‘MYSQL’ undeclared (first use in this function) _mysql.c:475: error: ‘conn’ undeclared (first use in this function) _mysql.c:500: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c:501: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c:525: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c:547: warning: implicit declaration of function ‘mysql_init’ _mysql.c:547: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:550: warning: implicit declaration of function ‘mysql_options’ _mysql.c:550: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:550: error: ‘MYSQL_OPT_CONNECT_TIMEOUT’ undeclared (first use in this function) _mysql.c:554: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:554: error: ‘MYSQL_OPT_COMPRESS’ undeclared (first use in this function) _mysql.c:555: error: ‘CLIENT_COMPRESS’ undeclared (first use in this function) _mysql.c:558: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:558: error: ‘MYSQL_OPT_NAMED_PIPE’ undeclared (first use in this function) _mysql.c:560: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:560: error: ‘MYSQL_INIT_COMMAND’ undeclared (first use in this function) _mysql.c:562: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:562: error: ‘MYSQL_READ_DEFAULT_FILE’ undeclared (first use in this function) _mysql.c:564: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:564: error: ‘MYSQL_READ_DEFAULT_GROUP’ undeclared (first use in this function) _mysql.c:567: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:567: error: ‘MYSQL_OPT_LOCAL_INFILE’ undeclared (first use in this function) _mysql.c:575: warning: implicit declaration of function ‘mysql_real_connect’ _mysql.c:575: error: ‘_mysql_ConnectionObject’ has no member named ‘connection’ _mysql.c:590: error: ‘_mysql_ConnectionObject’ has no member named ‘open’ _mysql.c: In function ‘_mysql_ConnectionObject_traverse’: _mysql.c:671: error: ‘_mysql_ConnectionObject’ has no member named ‘converter’ _mysql.c:

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• Automatic Properties, Collection Initializers, and Implicit Line Continuation support with VB 2010

  - by ScottGu

  [In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu] This is the eighteenth in a series of blog posts I’m doing on the upcoming VS 2010 and .NET 4 release. A few days ago I blogged about two new language features coming with C# 4.0: optional parameters and named arguments.  Today I’m going to post about a few of my favorite new features being added to VB with VS 2010: Auto-Implemented Properties, Collection Initializers, and Implicit Line Continuation support. Auto-Implemented Properties Prior to VB 2010, implementing properties within a class using VB required you to explicitly declare the property as well as implement a backing field variable to store its value.  For example, the code below demonstrates how to implement a “Person” class using VB 2008 that exposes two public properties - “Name” and “Age”:   While explicitly declaring properties like above provides maximum flexibility, I’ve always found writing this type of boiler-plate get/set code tedious when you are simply storing/retrieving the value from a field.  You can use VS code snippets to help automate the generation of it – but it still generates a lot of code that feels redundant.  C# 2008 introduced a cool new feature called automatic properties that helps cut down the code quite a bit for the common case where properties are simply backed by a field.  VB 2010 also now supports this same feature.  Using the auto-implemented properties feature of VB 2010 we can now implement our Person class using just the code below: When you declare an auto-implemented property, the VB compiler automatically creates a private field to store the property value as well as generates the associated Get/Set methods for you.  As you can see above – the code is much more concise and easier to read. The syntax supports optionally initializing the properties with default values as well if you want to: You can learn more about VB 2010’s automatic property support from this MSDN page. Collection Initializers VB 2010 also now supports using collection initializers to easily create a collection and populate it with an initial set of values.  You identify a collection initializer by declaring a collection variable and then use the From keyword followed by braces { } that contain the list of initial values to add to the collection.  Below is a code example where I am using the new collection initializer feature to populate a “Friends” list of Person objects with two people, and then bind it to a GridView control to display on a page: You can learn more about VB 2010’s collection initializer support from this MSDN page. Implicit Line Continuation Support Traditionally, when a statement in VB has been split up across multiple lines, you had to use a line-continuation underscore character (_) to indicate that the statement wasn’t complete.  For example, with VB 2008 the below LINQ query needs to append a “_” at the end of each line to indicate that the query is not complete yet: The VB 2010 compiler and code editor now adds support for what is called “implicit line continuation support” – which means that it is smarter about auto-detecting line continuation scenarios, and as a result no longer needs you to explicitly indicate that the statement continues in many, many scenarios.  This means that with VB 2010 we can now write the above code with no “_” at all: The implicit line continuation feature also works well when editing XML Literals within VB (which is pretty cool). You can learn more about VB 2010’s Implicit Line Continuation support and many of the scenarios it supports from this MSDN page (scroll down to the “Implicit Line Continuation” section to find details). Summary The above three VB language features are but a few of the new language and code editor features coming with VB 2010.  Visit this site to learn more about some of the other VB language features coming with the release.  Also subscribe to the VB team’s blog to learn more and stay up-to-date with the posts they the team regularly publishes. Hope this helps, Scott

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• Implicit casting in VB.NET

  - by Shimmy

  The question is intended for lazy VB programmers. Please. In vb I can do and I won't get any errors. Example 1 Dim x As String = 5 Dim y As Integer = "5" Dim b As Boolean = "True" Example 2 Dim a As EnumType = 4 Dim v As Integer = EnumType.EnumValue Example 3 Private Sub ButtonClick(sender As Object, e As EventArgs) Dim btn As Button = sender End Sub Example 4 Private Sub ButtonClick(sender As Button, e As EventArgs) Dim data As Contact = sender.Tag End Sub If I surely know the expected runtime type, is this 'forbidden' to rely on the vb-language built-in casting? When can I rely? Thanks

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• Implicit conversion : const reference vs non-const reference vs non-reference

  - by Nawaz

  Consider this code, struct A {}; struct B { B(const A&) {} }; void f(B) { cout << "f()"<<endl; } void g(A &a) { cout << "g()" <<endl; f(a); //a is implicitly converted into B. } int main() { A a; g(a); } This compiles fine, runs fine. But if I change f(B) to f(B&), it doesn't compile. If I write f(const B&), it again compiles fine, runs fine. Why is the reason and rationale? Summary: void f(B); //okay void f(B&); //error void f(const B&); //okay I would like to hear reasons, rationale and reference(s) from the language specification, for each of these cases. Of course, the function signatures themselves are not incorrect. Rather A implicitly converts into B and const B&, but not into B&, and that causes the compilation error.

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• Implicit typing of arrays that implement interfaces

  - by Sir Psycho

  Hi, I was under the impression that the C# compiler will implicitly type an array based off a type that they can all be implicitly converted to. The compiler generates No best type found for implicitly-typed array public interface ISomething {} public interface ISomething2 {} public interface ISomething3 {} public class Foo : ISomething { } public class Bar : ISomething, ISomething2 { } public class Car : ISomething, ISomething3 { } void Main() { var obj1 = new Foo(); var obj2 = new Bar(); var obj3 = new Car(); var objects= new [] { obj1, obj2, obj3 }; } I know that the way to correct this is to declare the type like: new ISomething [] { obj1, ...} But I'm after an under the covers type help here :-) Thanks

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• Implicit casting Integer calculation to float in C++

  - by Ziddiri

  Is there any compiler that has a directive or a parameter to cast integer calculation to float implicitly. For example: float f = (1/3)*5; cout << f; the "f" is "0", because calculation's constants(1, 3, 10) are integer. I want to convert integer calculation with a compiler directive or parameter. I mean, I won't use explicit casting or ".f" prefix like that: float f = ((float)1/3)*5; or float f = (1.0f/3.0f)*5.0f; Do you know any c/c++ compiler which has any parameter to do this process without explicit casting or ".f" thing?

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• C# Implicit array declaration

  - by The.Anti.9

  Basically, I want to be able to use string.Split(char[]) without actually defining a char array as a separate variable. I know in other languages you could do like string.split([' ', '\n']); or something like that. How would I do this in C#?

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• Overloading generic implicit conversions

  - by raichoo

  Hi I'm having a little scala (version 2.8.0RC1) problem with implicit conversions. Whenever importing more than one implicit conversion the first one gets shadowed. Here is the code where the problem shows up: // containers class Maybe[T] case class Nothing[T]() extends Maybe[T] case class Just[T](value: T) extends Maybe[T] case class Value[T](value: T) trait Monad[C[_]] { def >>=[A, B](a: C[A], f: A => C[B]): C[B] def pure[A](a: A): C[A] } // implicit converter trait Extender[C[_]] { class Wrapper[A](c: C[A]) { def >>=[B](f: A => C[B])(implicit m: Monad[C]): C[B] = { m >>= (c, f) } def >>[B](b: C[B])(implicit m: Monad[C]): C[B] = { m >>= (c, { (x: A) => b } ) } } implicit def extendToMonad[A](c: C[A]) = new Wrapper[A](c) } // instance maybe object maybemonad extends Extender[Maybe] { implicit object MaybeMonad extends Monad[Maybe] { override def >>=[A, B](a: Maybe[A], f: A => Maybe[B]): Maybe[B] = { a match { case Just(x) => f(x) case Nothing() => Nothing() } } override def pure[A](a: A): Maybe[A] = Just(a) } } // instance value object identitymonad extends Extender[Value] { implicit object IdentityMonad extends Monad[Value] { override def >>=[A, B](a: Value[A], f: A => Value[B]): Value[B] = { a match { case Value(x) => f(x) } } override def pure[A](a: A): Value[A] = Value(a) } } import maybemonad._ //import identitymonad._ object Main { def main(args: Array[String]): Unit = { println(Just(1) >>= { (x: Int) => MaybeMonad.pure(x) }) } } When uncommenting the second import statement everything goes wrong since the first "extendToMonad" is shadowed. However, this one works: object Main { implicit def foo(a: Int) = new { def foobar(): Unit = { println("Foobar") } } implicit def foo(a: String) = new { def foobar(): Unit = { println(a) } } def main(args: Array[String]): Unit = { 1 foobar() "bla" foobar() } } So, where is the catch? What am I missing? Regards, raichoo

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• Implicit constructor available for all types derived from Base excepted the current type?

  - by Vincent

  The following code sum up my problem : template<class Parameter> class Base {}; template<class Parameter1, class Parameter2, class Parameter> class Derived1 : public Base<Parameter> { }; template<class Parameter1, class Parameter2, class Parameter> class Derived2 : public Base<Parameter> { public : // Copy constructor Derived2(const Derived2& x); // An EXPLICIT constructor that does a special conversion for a Derived2 // with other template parameters template<class OtherParameter1, class OtherParameter2, class OtherParameter> explicit Derived2( const Derived2<OtherParameter1, OtherParameter2, OtherParameter>& x ); // Now the problem : I want an IMPLICIT constructor that will work for every // type derived from Base EXCEPT // Derived2<OtherParameter1, OtherParameter2, OtherParameter> template<class Type, class = typename std::enable_if</* SOMETHING */>::type> Derived2(const Type& x); }; How to restrict an implicit constructor to all classes derived from the parent class excepted the current class whatever its template parameters, considering that I already have an explicit constructor as in the example code ? EDIT : For the implicit constructor from Base, I can obviously write : template<class OtherParameter> Derived2(const Base<OtherParameter>& x); But in that case, do I have the guaranty that the compiler will not use this constructor as an implicit constructor for Derived2<OtherParameter1, OtherParameter2, OtherParameter> ? EDIT2: Here I have a test : (LWS here : http://liveworkspace.org/code/cd423fb44fb4c97bc3b843732d837abc) #include <iostream> template<typename Type> class Base {}; template<typename Type> class Other : public Base<Type> {}; template<typename Type> class Derived : public Base<Type> { public: Derived() {std::cout<<"empty"<<std::endl;} Derived(const Derived<Type>& x) {std::cout<<"copy"<<std::endl;} template<typename OtherType> explicit Derived(const Derived<OtherType>& x) {std::cout<<"explicit"<<std::endl;} template<typename OtherType> Derived(const Base<OtherType>& x) {std::cout<<"implicit"<<std::endl;} }; int main() { Other<int> other0; Other<double> other1; std::cout<<"1 = "; Derived<int> dint1; // <- empty std::cout<<"2 = "; Derived<int> dint2; // <- empty std::cout<<"3 = "; Derived<double> ddouble; // <- empty std::cout<<"4 = "; Derived<double> ddouble1(ddouble); // <- copy std::cout<<"5 = "; Derived<double> ddouble2(dint1); // <- explicit std::cout<<"6 = "; ddouble = other0; // <- implicit std::cout<<"7 = "; ddouble = other1; // <- implicit std::cout<<"8 = "; ddouble = ddouble2; // <- nothing (normal : default assignment) std::cout<<"\n9 = "; ddouble = Derived<double>(dint1); // <- explicit std::cout<<"10 = "; ddouble = dint2; // <- implicit : WHY ?!?! return 0; } The last line worry me. Is it ok with the C++ standard ? Is it a bug of g++ ?

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