ranges.chunks and map! does not work

[vit]

On Thursday, 5 July 2018 at 09:47:32 UTC, Andre Pany wrote:
> Hi,
>
> the purpose of this code is to generate CSV based on 3 double 
> arrays.
> I wonder why map cannot directly use the result of the chunks 
> function.
>
> import std.experimental.all;
>
> void main()
> {
>     double[] timestamps = [1.1];
>     double[] temperatures = [2.2];
>     double[] pressures = [3.3];
>
>     string content = roundRobin(timestamps, temperatures, 
> pressures)
>         .chunks(3)
>         //.map!(c => c.array)
>         .map!(c => "%.10g,%.10g,%.10g".format(c[0],c[1],c[2]))
>         .join("\n");
>
>     writeln(content);
> }
>
> The exact error message is (this line is 3 times repeated):
> app1.d(12): Error: no [] operator overload for type 
> Take!(Result)
> app1.d(12): Error: no [] operator overload for type 
> Take!(Result)
> app1.d(12): Error: no [] operator overload for type 
> Take!(Result)
> C:\SAPDevelop\D\dmd2\windows\bin\..\..\src\phobos\std\algorithm\iteration.d(499):        instantiated from here: MapResult!(__lambda1, Chunks!(Result))
> app1.d(12):        instantiated from here: map!(Chunks!(Result))
>
> Is it correct that I need to call ".map!(c => c.array)"?
>
> Kind regards
> André

roundRobin doesn't return RandomAccessRange => chunks doesn't 
return range of RandomAccessRange => Error: no [] operator 
overload

try this:

     string content = roundRobin(timestamps, temperatures, 
pressures)
         .array
         .chunks(3)
         //.map!(c => c.array)
         .map!(c => "%.10g,%.10g,%.10g".format(c[0],c[1],c[2]))
         .join("\n");