Parameters: preliminary requirement analysis

In the current stage, a design-draft is required that is sufficiently adequate
to be used as code placeholder and to evolve into the full specification eventually.

 - we need a single parameter container type with value semantics
 - parameters must support a selection of basic value types, with conversions
 - the value range can be limited, and a parameter can be associated
   with a ''Scale'' (stepped, continuous, logarithmic)
 - a parameter can be linked to a functional source
 - parameters are (virtually) copyable

src/lib/par/domain.hpp

@@ -0,0 +1,63 @@
+/*
+  DOMAIN.hpp  -  represent the value domain of parameters
+
+   Copyright (C)
+     2026             Hermann Vosseler <Ichthyostega@web.de>
+
+  **Lumiera** is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by the
+  Free Software Foundation; either version 2 of the License, or (at your
+  option) any later version. See the file COPYING for further details.
+
+*/
+
+
+/** @file domain.hpp
+ ** Specification of a base type and a value domain for parameters.
+ ** A Domain descriptor implicitly also encodes the concrete value type
+ ** and exposes a set of virtual functions to handle all supported value conversions.
+ ** Implementing this interface creates a conversion matrix and allows to implement
+ ** generic conversions by double-dispatch. Since virtual interfaces must be complete
+ ** at compile time however, such an approach requires to define a finite set of
+ ** supported parameter value types, which seems adequate, since the universe
+ ** of possible values is limited anyway: elementary values in parameters
+ ** must be primitive base types that can be created and destroyed
+ ** without side effect. Relying on the further features of
+ ** the parameter type system, compound types (vectors)
+ ** and limited sub-scales can be defined.
+ ** 
+ ** @todo WIP-WIP-WIP this is a draft and placeholder, as of 2026
+ */
+
+
+#ifndef LIB_PAR_DOMAIN_H
+#define LIB_PAR_DOMAIN_H
+
+
+
+
+namespace lib {
+namespace par {
+  
+  
+  
+  /**
+   * Interface: mark the allowed value domain of a parameter value.
+   * The identity of the actual implementation can be used as type descriptor,
+   * since all concrete full base domains are registered at compile time; the
+   * virtual Domain interface exposes the possible conversions.
+   * @todo 7/2026 not clear if we can support all conversions unconditionally,
+   *       or if some notion of an _impossible conversion_ is required. It is
+   *       clear however, that the access to an actual parameter **must fail**
+   *       at compile time, if a sensible conversion can not be provided.
+   */
+  class Domain
+    {
+    public:
+      virtual ~Domain();  ///< this is an interface
+    };
+  
+  
+  
+}} // namespace lib::par
+#endif /*LIB_PAR_DOMAIN_H*/

src/lib/par/param-type.cpp

@@ -0,0 +1,37 @@
+/*
+  ParamType  -  parameter scale and type descriptor
+
+   Copyright (C)
+     2026             Hermann Vosseler <Ichthyostega@web.de>
+
+  **Lumiera** is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by the
+  Free Software Foundation; either version 2 of the License, or (at your
+  option) any later version. See the file COPYING for further details.
+
+* *****************************************************************/
+
+
+/** @file param-type.cpp
+ ** Implementation of parameter type registration.
+ ** 
+ ** @todo WIP-WIP-WIP can be considered an initial draft and placeholder, as of 2026
+ */
+
+
+#include "lib/error.hpp"
+#include "lib/par/parameter.hpp"
+#include "lib/par/param-type.hpp"
+
+namespace lib {
+namespace par {
+  
+  
+  /* emit VTables in this translation unit... */
+  
+  ParamType::~ParamType() { }
+  Domain::~Domain() { }
+  
+  
+  
+}} // namespace lib::par

src/lib/par/param-type.hpp

@@ -0,0 +1,52 @@
+/*
+  PARAM-TYPE.hpp  -  parameter scale and type descriptor
+
+   Copyright (C)
+     2026             Hermann Vosseler <Ichthyostega@web.de>
+
+  **Lumiera** is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by the
+  Free Software Foundation; either version 2 of the License, or (at your
+  option) any later version. See the file COPYING for further details.
+
+*/
+
+
+/** @file param-type.hpp
+ ** Specification of the value domain and scale of a parameter.
+ ** A ParamType descriptor implicitly also encodes the concrete value type, the
+ ** allowed value range, clipping behaviour and specifics of the scale (discrete,
+ ** stepping, continuous, logarithmic...).
+ ** 
+ ** @todo WIP-WIP-WIP can be considered an initial draft and placeholder, as of 2026
+ */
+
+
+#ifndef LIB_PAR_PARAM_TYPE_H
+#define LIB_PAR_PARAM_TYPE_H
+
+
+#include "lib/par/domain.hpp"
+
+
+namespace lib {
+namespace par {
+  
+  
+  
+  /**
+   * Interface: represent a specific configuration of parameter value type,
+   * range and scale. Every ParamType descriptor is also a _prototype_ and has
+   * an unique identity, ensured by registration, so that it acts as a type identifier. 
+   * Furthermore, the interface exposes allowed conversion and conforming operations.
+   */
+  class ParamType
+    {
+    public:
+      virtual ~ParamType();  ///< this is an interface
+    };
+  
+  
+  
+}} // namespace lib::par
+#endif /*LIB_PAR_PARAM_TYPE_H*/

tests/16parameter.tests

@@ -5,3 +5,8 @@ TESTING "Library Test Suite: parameters" ./test-suite --group=param
 PLANNED "Parameter Values" Parameter_test <<END
 return: 0
 END
+
+
+PLANNED "Parameter Domain Type" ParameterDomain_test << END
+return: 0
+END

tests/lib/par/parameter-domain-test.cpp

@@ -0,0 +1,94 @@
+/*
+  ParameterDomain(Test)  -  document the handling of parameter type domain
+
+   Copyright (C)
+     2026,            Hermann Vosseler <Ichthyostega@web.de>
+
+  **Lumiera** is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by the
+  Free Software Foundation; either version 2 of the License, or (at your
+  option) any later version. See the file COPYING for further details.
+
+* *****************************************************************/
+
+/** @file parameter-domain-test.cpp
+ ** unit test \ref ParameterDomain_test
+ */
+
+
+#include "test/run.hpp"
+//#include "test/test-helper.hpp"
+#include "lib/par/domain.hpp"
+//#include "lib/format-cout.hpp"
+
+//#include <utility>
+//#include <string>
+//#include <vector>
+
+//using std::string;
+//using std::vector;
+//using std::swap;
+
+
+namespace lib {
+namespace par {
+namespace test{
+  
+//  using lumiera::error::LUMIERA_ERROR_LOGIC;
+  
+  namespace {//Test fixture....
+    
+    class Thing
+      { };
+    
+    template<typename X>
+    struct Some
+      {
+        X x;
+      };
+    
+    typedef Some<Thing> SomeThing;
+    
+  }//(End)Test fixture
+  
+  
+  
+  
+  
+  
+  
+  
+  
+  /**************************************************************************//**
+   * @test cover properties of generic parameter containers.
+   */
+  class ParameterDomain_test : public Test
+    {
+      
+      virtual void
+      run (Arg)
+        {
+          simpleUsage();
+          verify_typeMarker();
+        }
+      
+      
+      void
+      simpleUsage()
+        {
+        }
+      
+      
+      void
+      verify_typeMarker()
+        {
+        }
+    };
+  
+  
+  /** Register this test class... */
+  LAUNCHER (ParameterDomain_test, "unit lib");
+  
+  
+  
+}}} // namespace lib::par::test