I’m preparing for an upcoming C++ exam and came across this question about classes and constructors: How many constructors does the class Fraction have?” class Fraction { //… public: Fraction(int numerator = 0, int denominator = 1); //… }; I thought it’s only one, but they suggested there are three: Fraction(); Fraction(n); Fraction(n, d); Or … Read more
-put and -copyFromLocal are documented as identical, while most examples use the verbose variant -copyFromLocal. Why? Same thing for -get and -copyToLocal Answer -copyFromLocal is similar to -put command, except that the source is restricted to a local file reference. So basically, you can do with put, all that you do with -copyFromLocal, but not … Read more
Can some one explain to me the difference between categories and inheritance in Objective C? I’ve read the entry in Wikipedia and the discussion on categories there doesn’t look any different to that of inheritance. I also looked at the discussion on the topic in the book “Open iPhone Development” and I still don’t get … Read more
Something like var life= { users : { guys : function(){ this.SOMETHING.mameAndDestroy(this.girls); }, girls : function(){ this.SOMETHING.kiss(this.boys); }, }, mameAndDestroy : function(group){ }, kiss : function(group){ } }; this.SOMETHING is what I imagine the format is, but it might not be. What will step back up to the parent of an object? Answer I simply … Read more
I am getting this error on startup of Hadoop on OSX 10.7: Unable to load realm info from SCDynamicStore put: org.apache.hadoop.hdfs.server.namenode.SafeModeException: Cannot create directory /user/travis/input/conf. Name node is in safe mode. It doesn’t appear to be causing any issues with the functionality of Hadoop. Answer Matthew Buckett’s suggestion in HADOOP-7489 worked for me. Add the … Read more
I want to kill all my hadoop jobs automatically when my code encounters an unhandled exception. I am wondering what is the best practice to do it? Thanks Answer Depending on the version, do: version <2.3.0 Kill a hadoop job: hadoop job -kill $jobId You can get a list of all jobId’s doing: hadoop job … Read more
I am working on a collection of classes used for video playback and recording. I have one main class which acts like the public interface, with methods like play(), stop(), pause(), record() etc… Then I have workhorse classes which do the video decoding and video encoding. I just learned about the existence of nested classes … Read more
I have an OO hierarchy with docstrings that take as much maintenance as the code itself. E.g., class Swallow(object): def airspeed(self): “””Returns the airspeed (unladen)””” raise NotImplementedError class AfricanSwallow(Swallow): def airspeed(self): # whatever Now, the problem is that AfricanSwallow.airspeed does not inherit the superclass method’s docstring. I know I can keep the docstring using the … Read more
Crockford’s book, JavaScript: The Good Parts, says (on page 114) that constructor functions should always be given names with an initial capital letter (ie. Point), and that function names with initial capital letters should only be used with constructor functions (everything else should be lowerCase). This convention helps us avoid forgetting to use the new … Read more
There are some posts about this matter, but I didn’t clearly get when to use object-oriented coding and when to use programmatic functions in an include. Somebody also mentioned to me that OOP is very heavy to run, and makes more workload. Is this right? Let’s say I have a big file with 50 functions. … Read more
