Re: Convert array of tuples into array of arrays.

[Salih Dincer via Digitalmars-d-learn]

On Wednesday, 31 August 2022 at 17:26:56 UTC, Ali Çehreli wrote:
[...] You can make an array of arrays from those with the 
following syntax:


  auto arrayOfArrays = [ keys, values ];

Then I wrote a more general program after this first one:


I really like the generic methods. Because we can use enums for 
field names;  e.g:


```d
import std;

void main()
{
  enum {
key = "productCode",
val = "priceDolar"
  }

  auto makeTestTuple(int i)
  {
return tuple!(key, val)((i * 2).to!string,
   (double(i) / 10).to!string);
  }

  auto memberTuple(string member, T)(T tuples)
  {
return mixin("tuples." ~ member);
  }

  auto tuples = 1.iota(10)
 .map!makeTestTuple
 .array;

  string[string] myList;

  foreach(t; tuples)
  {
  const keys = memberTuple!key(t);
myList[keys] = memberTuple!val(t);
keys.writeln(": ", myList[keys]);
  }
} /*
2: 0.1
4: 0.2
6: 0.3
8: 0.4
10: 0.5
12: 0.6
14: 0.7
16: 0.8
18: 0.9
*/
```

SDB@79

Re: Convert array of tuples into array of arrays.

[Ali Çehreli via Digitalmars-d-learn]

On 8/31/22 07:34, musculus wrote:
> Hi. I have an array of tuples that I would like to convert to an array
> of arrays.

I misunderstood as well and wrote the following program which makes 
separate arrays. You can make an array of arrays from those with the 
following syntax:


  auto arrayOfArrays = [ keys, values ];

Then I wrote a more general program after this first one:

// Compiles slow but is convenient
import std;

auto makeTestTuple(int i) {
  return tuple!("key", "value")((i * 2).to!string,
(double(i) / 10).to!string);
}

void main() {
  auto tuples = iota(10)
.map!makeTestTuple
.array;

  string[] keys;
  string[] values;

  writeln("Imperative:");

  foreach (t; tuples) {
keys ~= t.key;
values ~= t.value;
  }

  writeln(keys);
  writeln(values);

  writeln("Alternative:");
  keys = tuples.map!(t => t.key).array;
  values = tuples.map!(t => t.value).array;
  writeln(keys);
  writeln(values);

  writeln("More generic:");
  keys = tuples.memberArray!"key";
  values = tuples.memberArray!"value";
  writeln(keys);
  writeln(values);
}

auto memberArray(string member, T)(T[] tuples) {
  return tuples.map!(t => mixin("t." ~ member)).array;
}

Here is the second program to have fun and "competitive advantage" with 
D. (That phrase came up recently, so I remembered it here. :) )


// Compiles slow but is convenient
import std;

auto makeTestTuple(int i) {
  return tuple!("key", "value", "somethingElse")(
(i * 2).to!string,
(double(i) / 10).to!string,
i * i);
}

mixin template matchingMember(string name, T) {
  mixin (T.stringof ~ "[] " ~ name ~ ';');
}

template TupleMemberArrays(T) {
  alias types = T.Types;
  alias fieldNames = T.fieldNames;
  enum memberCount = types.length;

  struct TupleMemberArrays {
static foreach (i; 0 .. memberCount) {
  mixin matchingMember!(fieldNames[i], types[i]);
}

this(T[] tuples) {
  foreach (t; tuples) {
static foreach (i; 0 .. memberCount) {
  mixin (format!q{
  %s ~= t.%s = t[%s];
}(fieldNames[i], fieldNames[i], i));
}
  }
}
  }
}

void main() {
  auto tuples = iota(10)
.map!makeTestTuple
.array;

  alias S = TupleMemberArrays!(ElementType!(typeof(tuples)));
  auto s = S(tuples);
  writeln(s.key);
  writeln(s.value);
  writeln(s.somethingElse);
}

That second program defines a type that matches the members of a tuple. 
Given a tuple with member names "key", "value", and "somethingElse"; and 
types string, string, int; it generates a struct similar to the following:


struct YourAliasHere {
  string[] key;
  string[] value;
  int[] somethingElse;
}

Limitation: That implementation uses field names, which not all tuples 
use. But it can be changed to generate names file field0, field1, etc. 
when needed.


Ali

Re: Convert array of tuples into array of arrays.

[Nick Treleaven via Digitalmars-d-learn]

On Wednesday, 31 August 2022 at 14:34:50 UTC, musculus wrote:
Hi. I have an array of tuples that I would like to convert to 
an array of arrays.

All of the elements in the tuples have matching types (string).
How would I go about doing this? Thanks!


Assuming std.typecons.Tuple, you can use `[tup.expand]` to make 
an array from a tuple.

If you mean a value sequence, you can use `[valSeq]`.

Convert array of tuples into array of arrays.

[musculus via Digitalmars-d-learn]

Hi. I have an array of tuples that I would like to convert to an 
array of arrays.

All of the elements in the tuples have matching types (string).
How would I go about doing this? Thanks!