On Sunday, 1 September 2019 at 20:42:28 UTC, Jabari Zakiya wrote:
> It still won't compile, with this error.
>
> Error: AliasSeq!(modpg, res_0, restwins, resinvrs) is not an lvalue and cannot be modified
>
> Here's a gist of the code.
>
> Top functions in code with issues are genPgParameters and selectPG
>
> https://gist.github.com/jzakiya/9227e4810e1bd5b4b31e949d1cbd5c5d

You can't do multiple assignments at once using AliasSeq; you have to assign each variable individually:

auto parameters = genPgParameters(pg);
modpg = parameters[0];
res_0 = parameters[1];
restwins = parameters[2];
resinvrs = parameters[3];

On Sunday, 1 September 2019 at 20:50:42 UTC, Paul Backus wrote:
> On Sunday, 1 September 2019 at 20:42:28 UTC, Jabari Zakiya wrote:
>> It still won't compile, with this error.
>>
>> Error: AliasSeq!(modpg, res_0, restwins, resinvrs) is not an lvalue and cannot be modified
>>
>> Here's a gist of the code.
>>
>> Top functions in code with issues are genPgParameters and selectPG
>>
>> https://gist.github.com/jzakiya/9227e4810e1bd5b4b31e949d1cbd5c5d
>
> You can't do multiple assignments at once using AliasSeq; you have to assign each variable individually:
>
> auto parameters = genPgParameters(pg);
> modpg = parameters[0];
> res_0 = parameters[1];
> restwins = parameters[2];
> resinvrs = parameters[3];

There's still are problem When I do this.

auto parameters = genPgParameters(pg);
  modpg = parameters[0];
  res_0 = parameters[1];
  restwins = parameters[2];
  resinvrs = parameters[3];

The compiler says this:

Error: cannot implicitly convert expression parameters.__expand_field_3 of type uint[] to shared(uint[])

If I comment out the last line the programs compiles (and crashes when run since all the parameters aren't available).

So why does it accept parameter[2] but not [3] as they are both defined the same?

Is this a compiler bug?

I have to say, getting this simple parameter passing to work in D has been an infuriating experience. :-(

On 08/27/2019 10:17 PM, Jabari Zakiya wrote:

> I can't do (a, b, c,d) = func1(i) directly.
> What do I do to assign the output of func1 to the individual variables?

I had some time to play with the following syntax, similar usage of which has been proposed a number of times as a replacement for tuple expansion. Assuming that foo() returns a struct of int, double, string; the following expression will set the variables to those members:

  int i;
  double d;
  string s;

  foo(42).into!(i, d, s);

Here is the complete program:

import std.stdio;
import std.string;

struct S {
  int i;
  double d;
  string s;
}

S foo(int i) {
  return S(i, 1.5, "hi");
}

template into(args...) {
  auto into(From)(From from)
  if (is (From == struct))
  {
    static foreach (i, m; __traits(allMembers, From)) {{
      alias argT = typeof(args[i]);
      alias memT = typeof(__traits(getMember, from, m));
      static assert (is (argT == memT),
                     format!"Cannot expand '%s %s.%s' into '%s %s' argument."
                     (memT.stringof, From.stringof, m, argT.stringof, args[i].stringof));
      mixin (format!"args[%s] = from.%s;"(i, m));
    }}
  }
}

void main() {
  int i;
  double d;
  string s;

  foo(42).into!(i, d, s);

  writeln(i);
  writeln(d);
  writeln(s);
}

I know that it does not address attributes like shared, etc. but it shows how expressive nested templates can be.

Ali