guile-libgraph.c:25:10: fatal error: libguile.h: No such file or directory #include
trying to install libgraph
Accessing class members on a NULL pointer I was experimenting with C++ and found the below code as very strange.   class Foo{ public:     virtual void say_virtual_hi(){         std::cout &lt;&lt; "Virtual Hi";     }      void say_hi()     {         std::cout &lt;&lt; "Hi";     } };  int main(int argc, char** argv) {     Foo* foo = 0;     foo-&gt;say_hi(); // works well     foo-&gt;say_virtual_hi(); // will crash the app     return 0; }   I know that the virtual method call crashes because it requires a vtable lookup and can only work with valid objects.   I have the following questions    How does the non virtual method say_hi work on a NULL pointer? Where does the object foo get allocated?   Any thoughts? Given a simple graph and its complement, prove that either of them is always connected. I was tasked to prove that when given 2 graphs $G$ and $\bar{G}$ (complement), at least one of them is a always a connected graph.  Well, I always post my attempt at solution, but here I'm totally stuck. I tried to do raw algebraic manipulations with # of components, circuit ranks, etc, but to no avail. So I really hope someone could give me a hint on how to approach this problem. Smoothing/generalizing polygon in QGIS? Is it possible to smooth or generalize a polygon in QGIS, perhaps by using a plugin like the generalizer-plugin for lines?  I could convert my polygons to lines, smooth them and convert them back to polygons but this is not working for my polygons because of several reasons. How can I reflect a transparent background? I'd like to make a glossy surface which reflects objects above it, but that also reflects a transparent background in the final render.  So in effect, the final render would contain only the reflections, not the surface itself.  Is this possible please? Filling cells with sequential numbers in an Excel (2003) macro I need to fill an excel column with a sequential series, in this case from -500 to 1000.  I've got a macro to do it, but it takes a lot of lines for something that seems like it should be a single function [something like FillRange(A2:A1502, -500, 1000, 1)].  But if that function exists, I can't find it.  Is the following as simple and elegant as it gets?  'Draw X axis scale Cells(1, 1).Value = "mV" Cells(2, 1).Value = -500 Cells(3, 1).Value = -499 Cells(4, 1).Value = -498  Dim selection1 As Range, selection2 As Range  Set selection1 = Sheet1.Range("A2:A4") Set selection2 = Sheet1.Range("A2:A1502")  selection1.AutoFill Destination:=selection2 How to make pdfsam work in (L)ubuntu 18.04? memoryless property of exponential distributions with random variables It is true that $P(X&gt;t+s|X&gt;t)=P(X&gt;s)$ for certain values $t$ and $s$.  However, how can I show that this still holds if:   $T$ is a continuous random variable. That is $P(X&gt;T+s|X&gt;T)=P(X&gt;s)$ Both $T$ and $S$ are continuous RVs: $P(X&gt;T+S|X&gt;T)=P(X&gt;S)$   All the random variables are independent. In the comedic music video  there are many clips of vintage scifi films, some of which I recognize.  This one however, of a large blue floating holographic head talking to some kind of military installation does not look at all familiar.  Does anyone recognize this film? Automatically keep current version of config files when apt-get install Sum of digits of repunits Our company would like to understand the effects:   If we have single table with Primary Key Identity column, int primary key IDENTITY(1,1),  and the Application is conducting multi-threading parallel processing, trying to conducts 1000s of simultaneous inserts on one table.   Would the identity primary key column fail, with a primary key violation in any way, for example: processors are trying to input the same identity number?  Or was SQL designed to be successful even in multithreading parallel insert?  Note: IDENTITY_INSERT is OFF Cyclic Quadrilateral Problems Let ABCD be a cyclic quadrilateral. The diagonals AC and BD meet at P, and DA and CB produced meet at Q. The midpoint of AB is E. Prove that if PQ is perpendicular to AC, then PE is perpendicular to BC. "Literally" and "Decimate" misuse Recently I've heard American TV commentators say "[a person] was literally decimated" and "[a Senator] was literally thrown under the bus". In the first case I think the person was not actually 10% killed, but in the second, I believe they meant that 57 members of the US Senate carried #58 onto Constitution Avenue and threw him under a (hopefully moving) bus.  Are usages like these normal or acceptable now? I find them grating, myself. How to deal with high correlation among predictors in multiple regression? Why does Yoda speak the way he does? Someone is offering to pay me in a sort of sugar daddy/sugar baby arrangement. They want to make online deposits to me, and they're asking me for my online banking username and password. Is that information alone enough for them to be able to take my money out of my account, or am I safe? I have 13.04 installed from a DVD that I got on eBay but the application launcher is missing. I've tried CCSM but it won't work! count vs length vs size in a collection From using a number of programming languages and libraries I have noticed various terms used for the total number of elements in a collection.  The most common seem to be length, count, and size.  eg.  array.length vector.size() collection.count   Is there any preferred term to be used? Does it depend on what type of collection it is? ie. mutable/immutable  Is there a preference for it being a property instead of a method? mkdir -p will create a directory; it will also make parent directories as needed.  Does a similar command exist for files, that will create a file and parent directories as needed? Why does Yoda speak the way he does? Yoda's unique speech consisting of reversed grammar is iconic.  Is there any reason he has adopted this speech pattern?  All other alien species encountered seem to have no trouble speaking normally. Why does Yoda speak in this way?