ipr::Unit seems to be missing

[MathiasMagnus]

The very first example from the doc doesn't build. It seems to be out of date, as there is no struct called Unit in source code.

[GabrielDosReis]

Yes, the doc is outdated.

[MathiasMagnus]

Can you point towards some "Hello, IPR" code where one could dissect a simple function declaration?

// IPR includes
#include <ipr/impl>
#include <ipr/io>

// Standard C++ includes
#include <iostream>
#include <string>

template<class E>
void inspect(const E& e)        // Print a expression and its type.
{
   ipr::Printer pp(std::cout);  // Create an XPR pretty printer
                                // tied to std::cout.
   pp << ipr::xpr_expr(e);      // Output e in XPR notation.
   pp << " has type ";
   pp << ipr::xpr_expr(e.type()); // Output type of e in XPR notation.
   std::cout << std::endl;
}

constexpr auto code =
   "double add(double a, double b) { return a + b; }";

int main()
{
   ipr::??? expr{ code };
   
   inspect(expr);

   return 0;
}

I would very much like to experiment with IPR/XPR and potentially contribute. How much have the internals changed since the doc was last updated? I see there are references to modules and interfaces which hint at being used for the developement of the modules TS. Am I right, or are those different notions?