Hi,

As an experiment I have implemented the following kind of pattern matching
(by parsing the part of the string before '=').

struct S {
int x;
int y;
}

struct T {
    int w;
    S s;
}
void main()
{
    mixin(matchAssign(q{auto T(first,S(second,third)) = T(1,S(2,3));}));
    first.writeln;  // 1
    second.writeln; // 2
    third.writeln;  // 3
}

In doing so I wanted to produce unique identifiers (something like gensym in racket.) I did this in a very hacky way:

auto hopefullyUniqueName(size_t n, size_t line=__LINE__) {
    return format!"____________________________var___________________________%s%s"(n,line);
}

where I pass in the hash of the right hand side in the assignment in place of n.

Is there some way to ask the compiler for a unique name or a better way of achieving this?

There's been attempts to expose it, exactly so that users can generate unique names, but that did not found its path in the compiler.

On Thursday, 9 June 2022 at 23:50:10 UTC, user1234 wrote:

You can generate unique names actually by using CTFE RNG, so it's not really necessary to have it exposed to achieve that.

See my hacky example of hidden class members here:

https://forum.dlang.org/thread/siczwzlbpikwlevviwxt@forum.dlang.org

In doing so I wanted to produce unique identifiers (something like gensym in racket.) I did this in a very hacky way:
[...]
Is there some way to ask the compiler for a unique name or a better way of achieving this?

On Thursday, 9 June 2022 at 21:20:27 UTC, JG wrote:

Here's a gensym implementation I came up with a while back:

enum gensym = q{"_gensym" ~ __traits(identifier, {})["__lambda".length .. $]};

// Works multiple times on the same line
pragma(msg, mixin(gensym)); pragma(msg, mixin(gensym));

This takes advantage of the fact that the compiler generates a unique identifier for every lambda function it encounters. While you can't actually use those identifiers in your code, they are visible in error messages and can be accessed via __traits(identifier).

On Thursday, 9 June 2022 at 21:20:27 UTC, JG wrote:

No, for now there if there are other ways they are as hacky as yours.

The compiler usually uses a global counter to generate temporaries.
There's been attempts to expose it, exactly so that users can generate unique names, but that did not found its path in the compiler.

On Thursday, 9 June 2022 at 23:50:10 UTC, user1234 wrote:

Here's another one. That's nice if people are able to find tricks but there's a need to have a clean way to do that. i.e language feature.