Angel Angel's questions

Grades:

• I am not asking what are the differences between dynamically typed and statically typed, be they advantages or disadvantages.

Can someone tell me how dynamic typing works in relation to the memory manager?

How the memory manager (or the part in charge) works to decide if it needs another memory address etc. (to store the data), creating it or expanding the current one if possible (speculation) etc.

For example (speculation): when the variable x = 5is initialized and assigned to it x = "dynamically", the Zmanager part verifies that there is space for the new type, and acts accordingly, reserving a new memory address for the new type and assigning the new address to the initial variable. This is speculation because I don't know how it works exactly "I know there will be different implementations for the same thing" depending on the interpreter/compiler/etc.

What I would like to know is the general idea of Z​​-> interpreter/compiler/etc. and the code in charge of such a task.

I've looked at some projects, including Google's V8 , but it's not a small project and I haven't been able to find the part that deals with such an issue, to figure out what the idea is of how it works Zfor the case of V8.

The answer does not have to be based on V8it can be on another language, interpreter etc, what interests me is the idea of ​​how it works in x case, or in most cases, (but not a speculation about how it works) , and if possible I would like a reference to the part of the code that reflects the above idea.

I'm trying to use something similar to interpolateProviderin AngularJS 2but I can't find something similar to this:

AngularJS 1.x $interpolateProvider

$interpolateProvider.startSymbol('//');
$interpolateProvider.endSymbol('//');

Looking at the documentation for AngularJS 2I couldn't find anything like the above.

How can I add one libraryusing gradleor not, in this particular case it is about adding the library to be able to use objects of the type JSONObjectto be able to test a code.

Question made based on this answer/question:

How to unescape a JSON string in Android Java?

What are the keyboard shortcuts to comment the code in Android Studio, both for one line or several selected lines //,

//Comentar lineas seleccionadas 1
//Comentar lineas seleccionadas

as for a selected code block /* */.

/*Comentar lineas seleccionadas
  Comentar lineas seleccionadas
  Comentar lineas seleccionadas*/

I am getting the following message in Android Studio 1.5.1:

Error: Not debuggable applications

I try to restart it and it still doesn't work. But before it did work and no plugin or library has been installed or changes have been made to the OS. View image:

How can I solve that?

Part of an application that I am developing, has to obtain the metadata of the images for its later use in it, so far what I am using is ExifInterface , with something similar to the following:

//..

String filename = "DirectorioDondeEstaElFichero/DSC_.JPG";

  try {
   ExifInterface exif = new ExifInterface(filename);
   FiltroExif(exif);
   //ShowExif(exif);
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();

   //..
  }

  //..

  private void FiltroExif(ExifInterface exif){
     String attr="attr ---\n";

     attr += getTagString(ExifInterface.TAG_DATETIME,         exif);
     attr += getTagString(ExifInterface.TAG_GPS_LATITUDE,     exif);
     attr += getTagString(ExifInterface.TAG_GPS_LATITUDE_REF, exif);
  }

  //..

But as the documentation says at some point:

This is a class for reading and writing Exif tags in a JPEG file.

There is some known way to read the metadata of an image PNGif it is possible without using any library not provided by android, although this is not a requirement , it would also be worth it if it was not provided by android.

This is commented in case someone has done something similar or helps provide a solution:

As a last option, it would be to review the SKIA code and try to do something there "although if possible I don't know if that would be muddying my hands at least in my case "

UPDATE :

• I don't need to write metadata to the image just read it.
• If it is an external library that has time to be created or used, to avoid bugs that may appear in the process of using it (but it is not a requirement).
• An example of its use or a link to some type of documentation that indicates that it works for the purpose would also be appreciated (but it is not a requirement).

Trying to connect an android device I am having errors of the type:

command shell:

./adb devices
List of devices attached
* daemon not running. starting it now on port 5037 *
* daemon started successfully *

command shell:

./adb devices
List of devices attached
xxxxxxxxxxxx    no permissions

After generating a test project in android studio, there comes a time when I get the following error message:

After clicking on the message, it starts the installation, but it turns out that the same error still appears.

android studio 1.5.1

I am (migrating to Android Studio) and getting failed downloads when trying to download the images dispositivos virtualesand I would like to be able to delete them, because they take up a lot and I have to download several images, I imagine they will be stored in some temporary directory or something like that, the question is, on a system GNU/Linuxwhere Android studio saves these images.

Android Studio 1.5.1

Update: I already found it with what I expanded the question, they can be deleted without further ado or android studio, it has some record elsewhere and they have to be deleted from the IDE itself

After downloading and running Android Studio bundle (for Linux)I get the following error after launching RUN(Mayus+F10):

Unable to obtain debug bridge

Android Studio 1.5.1

I'm digging through some files from Mesa 3-D graphics libraryand came across this code:

gl.h

//..
#if defined(__WIN32__) && !defined(__CYGWIN__)
#  if (defined(_MSC_VER) || defined(__MINGW32__)) && defined(BUILD_GL32) /* tag specify we're building mesa as a DLL */
#    define GLAPI __declspec(dllexport)
#  elif (defined(_MSC_VER) || defined(__MINGW32__)) && defined(_DLL) /* tag specifying we're building for DLL runtime support */
#    define GLAPI __declspec(dllimport)
//..

My question is what function does it have __declspec(dllexport)and __declspec(dllimport)when should they be used?

This is what I've used to call non-member functions in C++ from C code and it works fine.

file.cpp

extern  "C" void f(int);

    void f(int i){

        printf("c++!\n");
    }

main.c

#include <stdio.h>
#include <stdlib.h>

void f(int);

int main()
{
    printf("Hello world!\n");

    f(1);
    return 0;
}

shell:

Hello world!
c++!

How can I call member functions from C?

I use:

template<class T>
Arbol<T>::Arbol(){

}

when Tyou are going to do a class.

and use:

template<typename T>
Arbol<T>::Arbol(){

}

when it is going Tto be a type, for example bool, that is, charfundamental types.

But looking at a code fragment of a program (not created by me) I saw that it used typenamewhere I usually use class, and until now I had not noticed that. if now you ask me why, well, I wouldn't be able to say one hundred percent why, but perhaps somehow I (imagine) that the compiler differentiated when it was a type included in the language and acted accordingly.

My question is:

Is it the same to use one or the other?

Well, now I've tested both of them and they work fine, but I don't know if I'm missing something, or maybe there's some subtle difference between classand typenamein this context.

I have a char[] , named buffer , the data is stored using an ifstream in mode binary mode,

void File::mostrarBuffer(){
  for (int a = 0; a < std::strlen(buffer); a++){
    std::cout << std::hex << ((int)buffer[a]) << std::endl;
  }

  std::cout <<  "==="  << std::endl;

  for (int a = 0; a < std::strlen(buffer); a++){
    std::cout <<  buffer[a] << std::endl;
  }

  char charTest = '\211';

  std::cout <<  "==="  << std::endl;

  std::cout << std::hex << (int)charTest  << std::endl;
  std::cout << std::hex << (int)buffer[0] << std::endl;
}

The shell displays the following:

ffffff89
50
4e
47
===
\211
P
N
G
===
ffffff89
ffffff89

File part in hexdump (" little-endian"):

0000000 5089 474e 0a0d 0a1a 0000 0d00 4849 5244

Why does it print ffffff89and not 89, and only on the first element of the char []?

original question author

https://stackoverflow.com/questions/114180/pointer-vs-reference

Jack Reza https://stackoverflow.com/users/20349/jack-reza

What would be best practice when passing the original variable to the function to work with it by:

unsigned long x = 4;

void func1(unsigned long& val) {
     val = 5;            
}
func1(x);

or by:

unsigned long x = 4;

void func2(unsigned long* val) {
     *val = 5;
}
func2(&x);

Is there any reason to choose one over the other?

I was practicing with lambdas and came across the following code:

auto make_fibo() {
    return [](int n) {
        std::function<int(int)> recurse;

        recurse = [&](int n) {
            return (n <= 2) ? 1 : recurse(n - 1) + recurse(n - 2);
        };

        return recurse(n);
    };
}

I did not know what it was functionor how it worked after searching and reading several texts, for example the following:

http://www.cplusplus.com/reference/functional/function/

My question is yes, it std::functionis similar to the following for example:

typedef int (*FredMemFn)(int i);