Hi everyone,

Technically r1 and r2 are different types of range. Isn't it inconsistent to chain both? If not, why is the char type converted to int?

import std.stdio,
       std.range;

void main() {
  auto r1 = N!size_t(10, 1, 1);
  auto r2 = N!real(15, .5, 10);

  r1.chain(r2).writeln;
  // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5]

  auto a = [97, 98, 99];
  auto b = ['d', 'e', 'f'];

  a.chain(b).writeln;
  // [97, 98, 99, 100, 101, 102]
}

struct N(T)
{
  T last, step, first;
  bool empty() => first >= last;
  T front() => first;
  auto popFront() => first += step;
}
void main() {
  auto r1 = N!size_t(10, 1, 1);
  auto r2 = N!real(15, .5, 10);

  r1.chain(r2).writeln;
  // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5]

  auto a = [97, 98, 99];
  auto b = ['d', 'e', 'f'];

  a.chain(b).writeln;
  // [97, 98, 99, 100, 101, 102]
}

struct N(T)
{
  T last, step, first;
  bool empty() => first >= last;
  T front() => first;
  auto popFront() => first += step;
}

SDB@79

On Friday, 5 April 2024 at 16:05:20 UTC, H. S. Teoh wrote:

  auto a = [97, 98, 99];
  auto b = ['d', 'e', 'f'];

  a.chain(b).map!(chr => chr.to!char).writeln;
  // abcdef

Nice, there is a solution that requires memory allocation, but it still makes you think!

However, they can fix this in Phobos3 because now we have this too: https://dlang.org/changelog/2.108.0.html#range_predicate_element

PS. I think I unintentionally made a chain by repeating the source code above, sorry :)

SDB@79

On Friday, 5 April 2024 at 21:26:10 UTC, Salih Dincer wrote:

I checked:

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

struct N(T)
{
  T last, step, first;
  bool empty() => first >= last;
  T front() => first;
  auto popFront() => first += step;
}

void main() {
  auto r1 = N!size_t(10, 1, 1);
  auto r2 = N!real(15, .5, 10);

  // r1.chain(r2).writeln;
  // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5]
  r1.chain(r2).map!(x => typeid(x)).writeln;
  // [real, real, . . . , real]
}

and it seems to work as I said.

On Saturday, 6 April 2024 at 09:21:34 UTC, rkompass wrote:

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

struct N(T)
{
  T last, step, first;
  bool empty() => first >= last;
  T front() => first;
  auto popFront() => first += step;
}

void main() {
  auto r1 = N!size_t(10, 1, 1);
  auto r2 = N!real(15, .5, 10);

Thank you for checking again, but it is important to be solution oriented. How about Tuple?

Yes, it might be wise to use a tuple in this case:

  //...
  auto tuple = a.zip(b);
  tuple.writeln;
  // [Tuple!(int, dchar)(97, 'd'), Tuple!(int, dchar)(98, 'e'), Tuple!(int, dchar)(99, 'f')]

  tuple.map!(num => num[0].to!dchar).write;
  tuple.map!"a[1]".writeln; // abcdef
}

SDB@79