Compile-time:

Is there a 'foo1' that yields 1 from the snippet below?

void main() {

   import std.stdio;
   size_t var1 = 1;

   char[4] Txt = cast(char[4])("var1");
   writeln(foo1(Txt));
}

Similarly, execution-time, is there a foo2 that wields 2 from the snippet below:

void main() {

   import std.stdio;
   size_t var2 = 2;

   char[4] Txt;

// Txt = various things at run-time;
// But finally:
   Txt = cast(char[4])("var2");
   writeln(foo2(Txt));
}

On Friday, 29 December 2023 at 17:11:49 UTC, DLearner wrote:

compile-tome

void main() {

    import std.stdio;

    size_t var1 = 1;
    size_t var2 = 8;

    writeln(mixin(var1.stringof));
    writeln(mixin(var2.stringof));
}

run-tome

Given the information you provide I'd say you can use an associative array:

size_t*[string] registry;

void main() {

    import std.stdio;

    size_t var1 = 1;
    size_t var2 = 8;

    registry[var1.stringof] = &var1;
    registry[var2.stringof] = &var2;

    writeln(*registry[var1.stringof]);
    writeln(*registry[var2.stringof]);
}

but take care to the entries lifetime, that's basically not safe as this escapes stack addresses.

On Friday, 29 December 2023 at 21:25:44 UTC, user1234 wrote:

void main() {

   size_t var1 = 1;
   size_t var2 = 3;
   size_t var3 = 5;
// ... Many other variables defined.

   char[4] VarName;
//   ...

// And some complicated logic finishes:
   VarName = cast(char[4])("var2");

// _Without_ previously storing the addresses of
// all the 'var' variables, how do I get access
// to the variable currently (run-time) named in VarName?
//
// Is there a compiler-provided
// 'introspection' function that would do this?
//
// Labouring the point: If there is an int variable intVar,
// whose name ("intVar") is held in a string variable strVar,
// then there is a compiler function __fnAddrVar() such that
// assert(__fnAddrVar(strVar) == &intVar)
// is true?
}