Re: ranges.chunks and map! does not work
On Thursday, 5 July 2018 at 12:00:03 UTC, vit wrote:
On Thursday, 5 July 2018 at 09:47:32 UTC, Andre Pany wrote:
[...]
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");
Thanks a lot for all the answers.
Kind regards
Andre
Re: ranges.chunks and map! does not work
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");
Re: ranges.chunks and map! does not work
On Thursday, 5 July 2018 at 09:47:32 UTC, Andre Pany wrote:
Is it correct that I need to call ".map!(c => c.array)"?
Kind regards
André
Well, no. It depends on how you define the formatting string.
This would also work:
´´´
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 => "%(%g,%)".format(c))
.join("\n");
writeln(content);
}
´´´
Re: ranges.chunks and map! does not work
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);
}
I always find this kind of confusing as well. What kind of ranges
are returned by functions handling ranges and returning another
range?
It is clear what type of range can be passed by looking at the
constraint for chunks[1]:
Chunks!Source chunks(Source)(Source source, size_t chunkSize)
if (isInputRange!Source);
It would be awesome to have something like and output constraint:
out(Output; isForwardRange!Output &&
isInputRange!(ElementType!Output))
or something similar to know what the function will return..
In your case it seems like the typeof(c.front) is not a random
access range:
auto c = roundRobin(timestamps, temperatures, pressures)
.chunks(3);
pragma(msg, isRandomAccessRange!(typeof(c.front)));
// prints false
So you could do
auto content = roundRobin(timestamps, temperatures, pressures)
.evenChunks(timestamps.length)
.map!(c =>
c.map!(a => format("%.10g", a))
.join(",")
)
.join("\n");
although there might be more elegant solutions.
[1]: https://dlang.org/phobos/std_range.html#chunks
ranges.chunks and map! does not work
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
