I often need to iterate through a filtered collection (associative array) as following:

string strComputerIDunwanted = "WS2"; /// associative array key to exclude

foreach (strComputerID, udtComputer; udtComputers) { /// .remove!(a => a == strComputerIDunwanted) ... ?

   if (strComputerID != strComputerIDunwanted) {

      ...

   }

}

Is there a way to filter the collection at the foreach-level to avoid the inner if ?

On Monday, 21 June 2021 at 03:59:10 UTC, someone wrote:

string strComputerIDunwanted = "WS2"; /// associative array key to exclude

foreach (strComputerID, udtComputer; udtComputers) { /// .remove!(a => a == strComputerIDunwanted) ... ?

   if (strComputerID != strComputerIDunwanted) {

      ...

   }

}

An associative array is not a range but a struct, so it is extra work to create a range from the AA to apply range functions.

You can get a range from it by using something like std.array.byPair() but for this usage you would be better of with your own function or template.

On Monday, 21 June 2021 at 08:35:19 UTC, frame wrote:

Crystal-clear. Thanks !

On Monday, 21 June 2021 at 03:59:10 UTC, someone wrote:

string strComputerIDunwanted = "WS2"; /// associative array key to exclude

foreach (strComputerID, udtComputer; udtComputers) { /// .remove!(a => a == strComputerIDunwanted) ... ?

   if (strComputerID != strComputerIDunwanted) {

      ...

   }

}

something like this ?

import std.array;
import std.algorithm;

    udtComputers.byPair
        .filter!(p => p.key != strComputerIDunwanted)
        .each!( (p) { /* foreach body */ } );

On 6/21/21 5:00 PM, Elronnd wrote:

Alternatively (if you're ok with this sort of thing):

foreach (k, v; coll) if (k != unwanted) {
}

It's actually visually shorter than doing the filter.

And the benefit to using the if statement over the filter wrapper is that the compiler has to do a lot less work.

-Steve

On Monday, 21 June 2021 at 22:08:56 UTC, Steven Schveighoffer wrote:

Indeed; in a few very-specific situations I usually write code like this since it allows me to concentrate on the task at hand and not on the details to access the needed data, but for the clarity of the example I reformatted my code :)

Same when I code RO properties for classes, I usually do:

private pxxxWhatever1; public whatever() @property { return pxxxWhatever1; }
private pxxxWhatever2; public whatever() @property { return pxxxWhatever2; }
private pxxxWhatever3; public whatever() @property { return pxxxWhatever3; }

It is far easier to read large chunk of similar constructs alongside than one below the other, at least, to me.

On Monday, 21 June 2021 at 15:32:09 UTC, wjoe wrote:

import std.array;
import std.algorithm;

    udtComputers.byPair
        .filter!(p => p.key != strComputerIDunwanted)
        .each!( (p) { /* foreach body */ } );

This seems really interesting :)

Almost three weeks with D and I still must learn a lot of things, there's a lot to :) !

Thanks for your tip !