Removing an element from a list or array

[Patrick via Digitalmars-d-learn]

Thank you, that is a great sample.

On Wednesday, 6 August 2014 at 19:41:50 UTC, Jonathan M Davis 
wrote:
> On Wednesday, 6 August 2014 at 19:01:26 UTC, Patrick wrote:
>> I feel dumb.  I've been searching for how to do this, and each 
>> page or forum entry I read makes me more confused.
>>
>> Let's say I have a list of values (Monday, Tuesday, Wednesday, 
>> Thursday, Friday).  I can store this list in an Slist, Dlist, 
>> Array etc -- any collection is fine.
>>
>> I decide I want to remove Thursday from the list.
>>
>> How?  I see that linearRemove is meant to do this, but that 
>> takes a range.  How do I get a range of 'Thursday'?
>
> Slicing a container gives you a range for that container, and 
> it's that type that needs to be used to remove elements (either 
> that, or that type wrapped with std.range.Take), since 
> otherwise, the container wouldn't know which elements you were 
> trying to remove - just their values.
>
> You need to use std.algorithm.find to find the element that you 
> want to remove, in which case, you have a range starting at 
> that element (but it contains everything after it too). So, you 
> used std.range.take to take the number of elements that you 
> want from the range, and then you pass that result to 
> linearRemove. e.g.
>
> import std.algorithm;
> import std.container;
> import std.range;
>
> void main()
> {
>     auto arr = Array!string("Monday", "Tuesday", "Wednesday",
>                             "Thursday", "Friday");
>     auto range = arr[];
>     assert(equal(range, ["Monday", "Tuesday", "Wednesday",
>                          "Thursday", "Friday"]));
>     auto found = range.find("Thursday");
>     assert(equal(found, ["Thursday", "Friday"]));
>     arr.linearRemove(found.take(1));
>     assert(equal(arr[], ["Monday", "Tuesday", "Wednesday", 
> "Friday"]));
> }
>
> C++ does it basically the same way that D does, but it's 
> actually one place where iterators are cleaner, because you can 
> just pass the iterator to erase, whereas with a range, that 
> would remove all of the elements after that element, which is 
> why you need take, which makes it that much more complicated.
>
> Using opSlice like that along with range-based functions like 
> find which don't return a new range type will always be what 
> you'll need to do in the general case, but it would definitely 
> be nice if we added functions like removeFirst to remove 
> elements which matched a specific value so that the simple use 
> cases didn't require using find.
>
> - Jonathan M Davis