Re: how to filter associative arrays with foreach ?
On Monday, 21 June 2021 at 08:31:16 UTC, Ali Çehreli wrote:
Two options for byKey and byKeyValue:
import std;
void main() {
auto aa = [ "WS2" : 42, "WS3" : 43 ];
string strComputerIDunwanted = "WS2";
foreach (key; aa.byKey.filter!(k => k !=
strComputerIDunwanted)) {
writeln(key, ' ', aa[key]);
}
// 't' is the tuple of key and value
foreach (t; aa.byKeyValue.filter!(t => t.key !=
strComputerIDunwanted)) {
writeln(t.key, ' ', t.value);
}
}
Like 'em both, very flexible indeed, I think there are a couple
of places I could implement this. Thanks for your good advice as
usual Ali :) !
Re: how to filter associative arrays with foreach ?
On Monday, 21 June 2021 at 15:32:09 UTC, wjoe wrote:
something like this ?
``` D
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 !
Re: how to filter associative arrays with foreach ?
On Monday, 21 June 2021 at 22:08:56 UTC, Steven Schveighoffer
wrote:
It's actually visually shorter than doing the filter.
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:
```d
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.
Re: how to filter associative arrays with foreach ?
On Monday, 21 June 2021 at 21:00:42 UTC, Elronnd wrote:
Here's how I would do it:
foreach (k, v; coll) {
if (k == unwanted) continue;
...
}
You still have an if, but the actual loop body doesn't have to
be nested, so it's easy to follow the control flow.
almost the same
Re: how to filter associative arrays with foreach ?
On 6/21/21 5:00 PM, Elronnd wrote:
On Monday, 21 June 2021 at 03:59:10 UTC, someone wrote:
Is there a way to filter the collection at the foreach-level to avoid
the inner if ?
Here's how I would do it:
foreach (k, v; coll) {
if (k == unwanted) continue;
...
}
You still have an if, but the actual loop body doesn't have to be
nested, so it's easy to follow the control flow.
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
Re: how to filter associative arrays with foreach ?
On Monday, 21 June 2021 at 03:59:10 UTC, someone wrote:
Is there a way to filter the collection at the foreach-level to
avoid the inner if ?
Here's how I would do it:
foreach (k, v; coll) {
if (k == unwanted) continue;
...
}
You still have an if, but the actual loop body doesn't have to be
nested, so it's easy to follow the control flow.
Re: how to filter associative arrays with foreach ?
On Monday, 21 June 2021 at 03:59:10 UTC, someone wrote:
I often need to iterate through a filtered collection
(associative array) as following:
```d
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 ?
something like this ?
``` D
import std.array;
import std.algorithm;
udtComputers.byPair
.filter!(p => p.key != strComputerIDunwanted)
.each!( (p) { /* foreach body */ } );
```
Re: how to filter associative arrays with foreach ?
On Monday, 21 June 2021 at 08:35:19 UTC, frame wrote: 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. Crystal-clear. Thanks !
Re: how to filter associative arrays with foreach ?
On Monday, 21 June 2021 at 03:59:10 UTC, someone wrote:
I often need to iterate through a filtered collection
(associative array) as following:
```d
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 ?
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.
Re: how to filter associative arrays with foreach ?
On 6/20/21 8:59 PM, someone wrote:
I often need to iterate through a filtered collection (associative
array) as following:
```d
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 ?
Two options for byKey and byKeyValue:
import std;
void main() {
auto aa = [ "WS2" : 42, "WS3" : 43 ];
string strComputerIDunwanted = "WS2";
foreach (key; aa.byKey.filter!(k => k != strComputerIDunwanted)) {
writeln(key, ' ', aa[key]);
}
// 't' is the tuple of key and value
foreach (t; aa.byKeyValue.filter!(t => t.key != strComputerIDunwanted)) {
writeln(t.key, ' ', t.value);
}
}
Ali
