filtered imports

[rikki cattermole]

On 13/09/2018 11:54 PM, Jonathan Marler wrote:
> "Selective imports" limit the symbols imported from a module by 
> providing a list of all the symbols to include:
> 
> import std.stdio : writeln, writefln;
> 
> The complement of this would be a "Filtered import", meaning, import all 
> the symbols except the ones in the provided list. I imagine the syntax 
> would look something like:
> 
> import std.stdio ~ writeln, writefln;
> 
> 
> To provide a use case for this, say you have a module that uses a fair 
> amount of symbols from `std.file` but you want to make sure that all 
> calls to `chdir` are logged.  Using a filtered import would allow you to 
> exclude `chdir` from being available globally so you could create a 
> wrapper that all code is forced to go through.
> 
> import std.stdio;
> import std.file ~ chdir;
> 
> void chdir(R)(R path)
> {
>      writefln("chdir '%s'", path);
>      from!"std.file".chdir(path);
> }
> 
> It's an interesting variation on D's current repertoire of import 
> semantics. Possibly worth consideration as an addition to the language.
> 
> Grammar Changes:
> -----------------------------------------------------
> ImportBindings:                    (existing rule)
>      Import : ImportBindList        (existing rule)
>      Import ~ ImportExcludeList     (new rule)
> 
> ImportExcludeList:                 (new rule)
>      Identifier, ImportExcludeList  (new rule)
> -----------------------------------------------------

import std.stdio;
import std.file;

void chdir(R)(R path) {
	writeln("changing dir to ", path);
     std.file.chdir(path);
}


void main()
{
     chdir("/tmp");
}