Why is std.algorithm so complicated to use?

[Jacob Carlborg]

On 2012-07-10 14:53, Dmitry Olshansky wrote:

> Too bad, as there is no need to make an array when you map something.

How do you store your ranges in a struct or class? Most of them are 
voldemort types.

> Then you need something like transform. Anyway the result of map should
> be sortable it's a bug.

Thank you for clearing that up.

>>> Please count the number of allocations in your paste of Ruby.
>>
>> Probably four (if you count the initial allocation for the array
>> literal). Plus a couple for the "to_s" method.
>>
>
> Now scale the problem to at least ~ 10^6 ...
>
>> But I can use the same methods and modify the array in place instead:
>>
>> a = [5, 3, 5, 6, 8]
>> a.uniq!
>> a.map!{ |e| e.to_s }
>> a.sort!
>> p a
>>
>> Prints:
>>
>> ["3", "5", "6", "8"]
>>
>> The corresponding D version would be:
>>
>> auto a = [5, 3, 5, 6, 8].uniq.map!(x => x.to!(string)).array.sort.array;



> The last array is unnecessary as sort is in-place.

Again, I want an array, not a range.

> Also why would you not sort before map? It'd be faster this way as it's
> sorting integers.

Isn't it obvious that is just an example and not real code. I'm trying 
to keep the code as short as possible here.

> Thus it's only 2 and one of them is literal. The map can't be sorted
> because uniq produces lazy bidirectional range. Thus you turn it into
> array as simple as that.
>
> My version would be:
>
> auto a = [5, 3, 5, 6, 8].sort().uniq().map!(x => x.to!(string))();
>
> fixed?

Still need an array. Real code:

https://github.com/jacob-carlborg/dstep/blob/master/dstep/translator/IncludeHandler.d#L124

I want the end result to be sorted.

> Because uniq work only on sorted ranges? Have you tried reading docs?
> "
> Iterates unique consecutive elements of the given range (functionality
> akin to the uniq system utility). Equivalence of elements is assessed by
> using the predicate pred, by default "a == b". If the given range is
> bidirectional, uniq also yields a bidirectional range.
> "
> Though it doesn't explicitly mentions it, the example is:

Yes, exactly.

> int[] arr = [ 1, 2, 2, 2, 2, 3, 4, 4, 4, 5 ];
> assert(equal(uniq(arr), [ 1, 2, 3, 4, 5 ][]));

How should I know that from the example?

-- 
/Jacob Carlborg