Re: Repeat and chunks

[Saurabh Das via Digitalmars-d-learn]

On Monday, 24 October 2016 at 15:28:50 UTC, Saurabh Das wrote:
On Monday, 24 October 2016 at 14:25:46 UTC, Dorian Haglund 
wrote:
Hey,
The following code crashes with DMD64 D Compiler v2.071.2:

import std.algorithm;
import std.stdio;
import std.range;

int main()
{
  repeat(8, 10).chunks(3).writeln();

  return 0;
}

Error message:

pure nothrow @nogc @safe 
std.range.Take!(std.range.Repeat!(int).Repeat).Take 
std.range.Repeat!(int).Repeat.opSlice(ulong, ulong)

If I replace repeat with iota, or a literal range (like [1, 2 
,3, 4]), I don't get the crash.

I don't see why I should not be able to use chunks with repeat.
If some property of repeat's range is missing to use chunks, 
shouldn't I get an error message ?

Am I missing something ?

PS: the behavior has been reproduced on someone else computer.

Cheers :)

This works:

repeat(8, 12).chunks(3).writeln;

The documentation of 
https://dlang.org/phobos/std_range.html#.chunks mentions 
something about evenly divisible by chunkSize – perhaps that is 
the cause of the assert fail. Not 100% sure why that's there 
though.

Thanks,
Saurabh

Some more cases, perhaps someone more knowledgeable can help:

import std.algorithm;
import std.stdio;
import std.range;

int main()
{
    [8, 8, 8, 8, 8, 8].chunks(3).writeln; // prints [[8, 8, 8], 
[8, 8, 8]]
    repeat(8, 6).writeln;                 // prints [8, 8, 8, 8, 
8, 8]
    repeat(8, 6).chunks(3).writeln;       // prints [[8, 8, 8]]. 
Why?

    assert([8, 8, 8, 8, 8, 8] == repeat(8, 6).array); // Passes
    assert([8, 8, 8, 8, 8, 8].chunks(3).array == repeat(8, 
6).array.chunks(3).array); // Passes
    assert([8, 8, 8, 8, 8, 8].chunks(3).array == repeat(8, 
6).chunks(3).map!(a => a.array).array); // Fails

    return 0;
}