I want to make a simple wrapper B around a complex class A. A has many different constructors. The class B does not have any constructors, so how can I automatically pass the constructor arguments to the base class A, without needing to implement them all in B?  Here is a simple example of what I want to do:  class A { public:    A(int a);    A(const&amp; A);    // etc ... };  class B : public A {    int b; };  void main() {    B b(0);  // Since B does not have a constructor, I want it to dispatch to A::A(int) }   note: A is a class from some package so I can not simply add my int b to A.
Why does this code:  class A {     public:          explicit A(int x) {} };  class B: public A { };  int main(void) {     B *b = new B(5);     delete b; }   Result in these errors:   main.cpp: In function ‘int main()’: main.cpp:13: error: no matching function for call to ‘B::B(int)’ main.cpp:8: note: candidates are: B::B() main.cpp:8: note:                 B::B(const B&)   Shouldn't B inherit A's constructor?  (this is using gcc)
I would like to try a different video display driver, but I'm not sure which one I'm currently using.    What's the simple way to see what driver my system is using currently? How to read from two input files using while loop I wanted to know if there is any way of reading from two input files in a nested while loop one line at a time. For example, lets say I have two files FileA and FileB.   FileA:  [jaypal:~/Temp] cat filea this is File A line1 this is File A line2 this is File A line3   FileB:  [jaypal:~/Temp] cat fileb this is File B line1 this is File B line2 this is File B line3   Current Sample Script:  [jaypal:~/Temp] cat read.sh  #!/bin/bash while read lineA     do echo $lineA      while read lineB         do echo $lineB          done &lt; fileb done &lt; filea   Execution:  [jaypal:~/Temp] ./read.sh  this is File A line1 this is File B line1 this is File B line2 this is File B line3 this is File A line2 this is File B line1 this is File B line2 this is File B line3 this is File A line3 this is File B line1 this is File B line2 this is File B line3   Problem and desired output:  This loops over FileB completely for each line in FileA. I tried using continue, break, exit but none of them are meant for achieving the output I am looking for. I would like the script to read just one line from File A and then one line from FileB and exit the loop and continue with second line of File A and second line of File B. Something similar to the following script -  [jaypal:~/Temp] cat read1.sh  #!/bin/bash count=1 while read lineA     do echo $lineA          lineB=`sed -n "$count"p fileb`         echo $lineB         count=`expr $count + 1` done &lt; filea  [jaypal:~/Temp] ./read1.sh  this is File A line1 this is File B line1 this is File A line2 this is File B line2 this is File A line3 this is File B line3   Is this possible to achieve with while loop? I want to create a wave made out of particles/dots. The wave should look like this:  I tried to achieve this effect by adding an ocean modifier to a plane. Then I added a particle system to the plane but now I don't know how to go on. How can I make the particles lay on the 'ocean' and move when the ocean is moving? PS: I know there is a way to do this with a material in the Blender Render. But firstly I want to create the whole thing in Cycles and secondly I want to have particles. Highly unbalanced test data set and balanced training data in classification I have a training set with about 3000 positive instances and 3000 negative instances. But my test data set is pretty much un-balanced. The positive set only has 50 instances and negative has 1500 instances.This causes the precision very low. Are there any approaches to solve this problem? I use SVM to build classifier. Maybe the underlying question is what the Voltage-Current curve looks like. Can I drive it from a voltage source (like you drive a heater) or from a current source (like you drive an LED)? Or even different than those two options?  ADDITIONAL1: Say (hypothetically) I have two commercially available identical Peltier's, they are spec'd 6V/3A. Can I connect these in series to a 12Vdc power supply without any worries?  CONCLUSION1: Current/Voltage load curve is reasonably linear, both driving from current or voltage source will do fine as long as the device is operated within its spec. (Olin Lathrop, Russell McMahon)  CONCLUSION2: Don't drive a Peltier from PWM, power loss due to current increase, grows more rapidly than cooling power. (Olin Lathrop)  CONCLUSION3: Beware the mechanical wear of the device with continues cycling. Eg. don't use a thermostat on/off controller. (Russell McMahon) I have this new problem since 2014 begin. I cant remotely login to this enterprise network for giving them support. Its keep showing this new error.  How to fix it please?    EDIT: How can I distribute a native executable for a Python program? What would be the effects of warp collisions? Triggered by a  I was wondering what actually would happen to a ship (e.g. the Enterprise-D NCC-1701) that collides with a stationary object such as a) another ship of a similar configuration or b) a gigantic structure like a moon or even a planet.  We know the deflector is supposed to keep interstellar dust (not to be confused with ordinary dust, which is a different thing) from ripping large holes in the ship.  At first, one thinks "Obvious. ." But does it really? Would the deflector manage to actually deflect both masses? If not, where is the threshold of what a deflector can handle? Would the ship maybe tunnel right through the object, because of wibbly-wobbly space wobblification by the warp field? It does do some weird things to the space right in front and behind the vessel.  Important remark: We cannot approach this with what we know about physics at all. For all intents and purposes, both ships must measure the other ship travelling faster than light, resulting in it having infinite (or rather undefined) mass and by extension momentum. If we start with that reasoning any ship jumping to warp would suck in the entire universe (it takes a moment, but think about it). So, obviously we cannot apply our intuition (even our relativistic intuition) here. Sums and products of algebraic numbers How does one go about proving that the sums and products of two algebraic numbers over a field $F$ (say $a,b\in K$, where $K/F$ is a field extension) is also algebraic?   If we call $f_a$ and $f_b$ the min. poly's of $a$ and $b$, then I'm assuming the answer involves such polynomials. Perhaps looking at their roots in splitting fields for both of them? And finding a "big" splitting field, constructed from those two other ones?      In particular, I'd like a way of explicitly constructing the minimal polynomials $\ f_{ab}$ of $ab$ and $f_{a+b}$ of $a+b$.     I read somewhere that $g(x)=\Pi_j\Pi_i (x-\alpha_i\beta_j)$ works for $ab$, where the $\alpha_i$ and $\beta_j$ are the roots of $f_a$ and $f_b$, respectively, but I do not know why $g(x)\in F[x]$.  Similar remarks for $a+b$ Java FileReader encoding issue I tried to use java.io.FileReader to read some text files and convert them into a string, but I found the result is wrongly encoded and not readable at all.  Here's my environment:   Windows 2003, OS encoding: CP1252 Java 5.0   My files are UTF-8 encoded or CP1252 encoded, and some of them (UTF-8 encoded files)  may contain Chinese (non-Latin) characters.  I use the following code to do my work:     private static String readFileAsString(String filePath)     throws java.io.IOException{         StringBuffer fileData = new StringBuffer(1000);         FileReader reader = new FileReader(filePath);         //System.out.println(reader.getEncoding());         BufferedReader reader = new BufferedReader(reader);         char[] buf = new char[1024];         int numRead=0;         while((numRead=reader.read(buf)) != -1){             String readData = String.valueOf(buf, 0, numRead);             fileData.append(readData);             buf = new char[1024];         }         reader.close();         return fileData.toString();     }   The above code doesn't work. I found the FileReader's encoding is CP1252 even if the text is UTF-8 encoded. But the JavaDoc of java.io.FileReader says that:     The constructors of this class assume   that the default character encoding   and the default byte-buffer size are   appropriate.   Does this mean that I am not required to set character encoding by myself if I am using FileReader? But I did get wrongly encoded data currently, what's the correct way to deal with my situtaion? Thanks. Probability of an even number of sixes We throw a fair die $n$ times, show that the probability that there are an even number of sixes is $\frac{1}{2}[1+(\frac{2}{3})^n]$. For the purpose of this question, 0 is even.   I tried doing this problem with induction, but I have problem with induction so I was wondering if my solution was correct:   The base case: For $n=0$, our formula gives us $\frac{1}{2}[1+(\frac{2}{3})^0] =1$. This is true, because if we throw the die zero times, we always get zero sixes.  Suppose it's true for $n=k$. Then the odds of an even number of sixes is $\frac{1}{2}[1+(\frac{2}{3})^n]$, and thus the odds of an odd number of sixes is $1 - \frac{1}{2}[1+(\frac{2}{3})^n]$.    For $n=k+1$, there are two ways the number of sixes are even:  a. The number of sixes for $n=k$ was even, and we do not throw a six for $n=k+1$: $ \frac{5}{6} \cdot  \frac{1}{2}[1+(\frac{2}{3})^n]$  b. The number of sixes for $n=k$ was odd, and we throw a six for $n=k+1$: $\frac{1}{6}(1 - \frac{1}{2}[1+(\frac{2}{3})^n])$  So the probability $p$ for an even number of sixes at $n=k+1$ is $ \frac{5}{6} \cdot  \frac{1}{2}[1+(\frac{2}{3})^n] + \frac{1}{6}(1 - \frac{1}{2}[1+(\frac{2}{3})^n])$  I have two questions   How do I get from $ \frac{5}{6} \cdot  \frac{1}{2}[1+(\frac{2}{3})^n] + \frac{1}{6}(1 - \frac{1}{2}[1+(\frac{2}{3})^n])$ to $\frac{1}{2}[1+(\frac{2}{3})^n]$? I seem to have done something wrong, I can't get the algebra correct, I get $p = \frac{1}{3}[1+(\frac{2}{3})^n] + \dfrac{1}{6}$ Other than that, is my use of induction correct? Is it rigorous enough to prove the formula? Let $a_n=\cos(a_{n-1}), L=[a_1,a_2,...,a_n,...].$ Is there an $a_0$ such that $L$ is dense in$[-1,1]?$ Possible Duplicate:          Let $X$ be a compact metric space and $f$ be an isometric map from $X$ to $X$. Prove $f$ is a surjective map. Pick random row from a file Proof a set cannot contain its own powerset - Russell's Paradox Using naive set theory and not using the cardinal number of a power set, how can you prove a set cannot contain its own power set? Is this connected to Russell's Paradox? When to use ' (or quote) in Lisp? After making it through the major parts of an introductory Lisp book, I still couldn't understand what the special operator (quote) (or equivalent ') function does, yet this has been all over Lisp code that I've seen.    What does it do? Dimensionality of null space when Trace is Zero This is the fourth part of a four-part problem in Charles W. Curtis's book entitled Linear Algebra, An Introductory Approach (p. 216).  I've succeeded in proving the first three parts, but the most interesting part of the problem eludes me.  Part (a) requires the reader to prove that $\operatorname{Tr}{(AB)} = \operatorname{Tr}{(BA)}$, which I was able to show by writing out each side of the equation using sigma notation.  Part (b) asks the reader to use part (a) to show that similar matrices have the same trace.  If $A$ and $B$ are similar, then  $\operatorname{Tr}{(A)} = \operatorname{Tr}{(S^{-1}BS)}$  $= \operatorname{Tr}(BSS^{-1})$  $= \operatorname{Tr}(B)$,  which completes part (b).  Part (c) asks the reader to show that the vector subspace of matrices with trace equal to zero have dimension $n^2 - 1$.  Curtis provides the hint that the map from $M_n(F)$ to $F$ is a linear transformation.  From this, I used the theorem that $\dim T(V) + \dim n(T) = \dim V$ to obtain the dimension of the null space.  Part (d), however, I'm stuck on.  It asks the reader to show that subspace described in part (c) is generated by matrices of the form $AB - BA$, where $A$ and $B$ are arbitrary $n \times n$ matrices.  I tried to form a basis for the subspace, but wasn't really sure what it would look like since an $n \times n$ matrix has $n^2$ entries in it, but the basis would need $n^2 - 1$ matrixes.  I also tried to think of a linear transformation whose image would have the form of $AB - BA$, but this also didn't help me.  I'm kind of stuck...  Many thanks in advance! Is it possible to reconstruct the Hamiltonian from knowledge of its ground state wave function? Is it possible to "construct" the Hamiltonian of a system if its ground state wave function (or functional) is known? I understand one should not expect this to be generically true since the Hamiltonian contains more information (the full spectrum) than a single state vector. But are there any special cases where it's possible to obtain the Hamiltonian? Some examples would be really helpful. How can I increase my Vault Dweller's Happiness? Show question ID When I want to close a question as duplicate using the app, I have to enter the question ID as usual. Problem is, as far as I can tell, the question IDs are shown nowhere! Please add the ID somewhere.