I have a list that contains arguments I want to pass to a function. How do I call that function? For example, imagine I had this function: sub foo { my ($arg0, $arg1, $arg2) = @_; print "$arg0 $arg1 $arg2\n"; } And let's say I have: my $args = [ "la", "di", "da" ]; How do I call foo without writing foo($$args[0], $$args[1], $$...
NSDecimalNumber *lat = [[NSDecimalNumber alloc]initWithDouble:sqlite3_column_double(selectStatement, 1)]; [latt addObject:lat]; [lat release]; CLLocationCoordinate2D annot; annot.latitude = [[latt objectAtIndex:k]doubleValue]; The above 2 codes shows the creation and retrieving of double valu...
Hi, I'm a programming student trying to better understand pointers, one of the things I learned is that you can set a pointer to NULL. My question is, what's the difference between these two statements? When would each of them return true/false? if (some_ptr == NULL) if (*some_ptr == NULL) Thanks! ...
I have a class with a method that returns a hash. Ordinarily, I would get the result like so: %resp = $myclass->sub($foo); And then access members of the returned hash like this: $resp{key}{subkey}; in the case of a 2d hash. I figure there must be a way to combine this into a single, elegant line, something like this: $myclass->...
I'm trying to debug a program I've written. According to the debugger a particular void * holds the value 0x804b008. I'd like to be able to dereference this value (cast it to an int * and get it's value). I'm getting a Segmentation Error with this code. (The program with the void * is still running in the background btw - it's 'paused')...
I'm still trying to sort out my hash dereferencing. My current problem is I am now passing a hashref to a sub, and I want to dereference it within that sub. But I'm not finding the correct method/syntax to do it. Within the sub, I want to iterate the hash keys, but the syntax for a hashref is not the same as a hash, which I know how t...
I have 2 arrays. $result = array(); $row = array(); Row's elements are all references and is constantly changing. For each iteration of $row I want to copy the values of row into an entry of $result and not the references. I have found a few solutions but they all seem rather awful. $result[] = unserialize(serialize($row)); $result[...
Is there any difference in performance - or otherwise - between: ptr->a(); and (*ptr).a(); ? ...
The standard says that dereferencing the null pointer leads to undefined behaviour. But what is "the null pointer"? In the following code, what we call "the null pointer": struct X { static X* get() { return reinterpret_cast<X*>(1); } void f() { } }; int main() { X* x = 0; (*x).f(); // the null pointer? (1) x = X::get(); ...
How do I create a reference to the value in a specific hash key. I tried the following but $$foo is empty. Any help is much appreciated. $hash->{1} = "one"; $hash->{2} = "two"; $hash->{3} = "three"; $foo = \${$hash->{1}}; $hash->{1} = "ONE"; #I want "MONEY: ONE"; print "MONEY: $$foo\n"; ...
Hi, I am pretty rusty at C, and I'm getting a dereferencing error. Hopefully someone can help me with this? ^_^ I have a struct defined as: struct { char name[32]; int size; int start; int popularity; } stasher_file; and an array of pointers to those structs: struct stasher_file *files[TOTAL_STORAGE_SIZE]; In my code, I'm ...
Hi, I have simplified an issue that I've been having trying to isolate the problem, but it is not helping. I have a 2 dimensional char array to represent memory. I want to pass a reference to that simulation of memory to a function. In the function to test the contents of the memory I just want to iterate through the memory and print o...
Hi, I have this destructor that create error at runtime "vector iterator not dereferencable". The gridMatrix is a std::vector<std::vector<std::vector<AtomsCell< Atom<T> * > * > * > * > I added the typename and also the typedef but I still have the error. I will move for this idea of vect of vect* of vect* to use boost::multi_array I ...
Why is dereferencing called dereferencing? I'm just learning pointers properly, and I'd like to know why dereferencing is called that. It confused me as it sounds like you are removing a reference, rather than going via the pointer to the destination. Can anyone explain why it is called this? To me something like destination or pointe...
Suppose I have the following C++ class: class Foo { double bar(double sth); }; double Foo::bar(double sth) { double a,b,c,d,e,f a = b = c = d = e = f = 0; /* do stuff with a..f and sth */ } The function bar() will be called millions of times in a loop. Obviously, each time it's called, the variables a..f have to be allocated....
Hi, This code works: my $href = shift @_; # get reference to hash my %h = %{$href}; # dereference hash This one does not: my %h = %{shift @_}; As well as this one: my %h = ${$_[0]} Why? ============================= One more time to be precisly: 1 #!/usr/bin/perl -w 2 use strict; 3 use warnings; 4 ...
Hi, I the code bellow line 9 creates a local copy of a hash. Any changes to the %d will not provide changes to global %h variable (line: 5). I have to use reference (line: 8) to provide changes to %h. Is there any way to dereference hash in a sub without creating a local copy? I am asking since I have complicated record with many refer...
This should be super simple, but I'm not sure why the compiler is complaining here. #include <stdio.h> #include <stdlib.h> int main(int argc, char *argv[]) { int *n = 5; printf ("n: %d", *n); exit(0); } Getting the following complaints: foo.c: In function ‘main’: foo.c:6: warning: initialization makes pointer from i...
i have a complex program with weird bug that some int value is down to zero unexpectedly. so i want tracking this built-in type value, then i could debug easily. to do that, i made following ValueWatcher template class so i could track almost changes of value except when ValueWatcher is dereferencing. (i made these dereferencing operat...
I'm trying to access the object (called a Vector) pointed to by a pointer held in a vector container, but I can't seem to get to it. Here are the important code snippets: int main{ Vector<double>* test = new Vector<double>(randvec<double>()); test->save(); cout << Element::vectors[0]; return 0; } Where Vector is a templ...