global vs context variable

[Artur Skawina]

On 12/11/13 09:21, luka8088 wrote:
> Hi everyone!
> 
> I would like to address the issue of global variables (or states). In
> general my opinion is that they are bad solely because they (in most
> cases) lack the ability of alternative values (or states) or ability to
> alter them in user friendly way.
> 
> For example, take write function from std.stdio. For a third party

[...]

> void writeOutput () {
>   writeln("example output");
> }
> 
> void main () {
>   writeOutput();
> 
>   standardOutputContext(file("example.txt"), {
>     writeOutput();
>   });
> }

   import std.stdio;

   void writeOutput () {
      writeln("example output");
   }

   void main () {
      writeOutput();

      {
         auto ex = Push!stdout(File("example.txt", "w"));
         writeOutput();
      }

      writeOutput();
   }

   struct Push(alias A, T=typeof(A)) {
      T old;
      this(T a) { old = A; A = a; }
      ~this()   { A = old; }
   }


Last time I checked, 'with' was still broken (the object is destroyed
too soon), but once that is fixed you should be able to do:

         with (Push!stdout(File("example.txt", "w")))
            writeOutput();

artur