improve Core API doc

Author: jll63

doc/modules/ROOT/examples/CMakeLists.txt

@@ -26,10 +26,6 @@ foreach (cpp ${cpp_files})
     add_dependencies(tests ${stem})
 endforeach()
 
-if (NOT WIN32)
-  add_subdirectory(shared_libs)
-endif()
-
 function(add_step_by_step dir)
   set(add_test "")
   if(ARGC GREATER 1)
@@ -51,5 +47,10 @@ function(add_step_by_step dir)
   endforeach()
 endfunction()
 
+add_step_by_step(core_api)
 add_step_by_step(rolex)
 add_step_by_step(ambiguities OFF)
+
+if (NOT WIN32)
+  add_subdirectory(shared_libs)
+endif()

doc/modules/ROOT/examples/core_api.cpp

@@ -0,0 +1,99 @@
+// Copyright (c) 2018-2025 Jean-Louis Leroy
+// Distributed under the Boost Software License, Version 1.0.
+// See accompanying file LICENSE_1_0.txt
+// or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <iostream>
+
+#include <boost/openmethod/initialize.hpp>
+#include <boost/openmethod/core.hpp>
+
+struct Node {
+    virtual ~Node() {
+    }
+    virtual int value() const = 0;
+};
+
+struct Variable : Node {
+    Variable(int value) : v(value) {
+    }
+    int value() const override {
+        return v;
+    }
+    int v;
+};
+
+struct Plus : Node {
+    Plus(const Node& left, const Node& right) : left(left), right(right) {
+    }
+    int value() const override {
+        return left.value() + right.value();
+    }
+    const Node& left;
+    const Node& right;
+};
+
+struct Times : Node {
+    Times(const Node& left, const Node& right) : left(left), right(right) {
+    }
+    int value() const override {
+        return left.value() * right.value();
+    }
+    const Node& left;
+    const Node& right;
+};
+
+using namespace boost::openmethod;
+
+// tag::method[]
+#include <boost/openmethod/macros.hpp>
+
+struct BOOST_OPENMETHOD_ID(postfix);
+
+using postfix = method<
+    BOOST_OPENMETHOD_ID(postfix),
+    void(virtual_ptr<const Node> node, std::ostream& os)>;
+// end::method[]
+
+// tag::variable_overrider[]
+auto postfix_variable(virtual_ptr<const Variable> node, std::ostream& os) {
+    os << node->v;
+}
+
+static postfix::override<postfix_variable> override_postfix_variable;
+// end::variable_overrider[]
+
+// tag::binary_overriders[]
+#include <boost/openmethod/macros.hpp>
+
+auto postfix_plus(virtual_ptr<const Plus> node, std::ostream& os) {
+    postfix::fn(node->left, os);
+    os << ' ';
+    postfix::fn(node->right, os);
+    os << " +";
+}
+
+auto postfix_times(virtual_ptr<const Times> node, std::ostream& os) {
+    postfix::fn(node->left, os);
+    os << ' ';
+    postfix::fn(node->right, os);
+    os << " *";
+}
+
+BOOST_OPENMETHOD_REGISTER(postfix::override<postfix_plus, postfix_times>);
+// end::binary_overriders[]
+
+// tag::use_classes[]
+BOOST_OPENMETHOD_REGISTER(use_classes<Node, Variable, Plus, Times>);
+// end::use_classes[]
+
+// tag::main[]
+auto main() -> int {
+    boost::openmethod::initialize();
+    Variable a{2}, b{3}, c{4};
+    Plus d{a, b};
+    Times e{d, c};
+    postfix::fn(e, std::cout);
+    std::cout << " = " << e.value() << "\n"; // 2 3 + 4 * = 20
+}
+// end::main[]

doc/modules/ROOT/examples/core_api/1/core_api.cpp

@@ -0,0 +1,77 @@
+// Copyright (c) 2018-2025 Jean-Louis Leroy
+// Distributed under the Boost Software License, Version 1.0.
+// See accompanying file LICENSE_1_0.txt
+// or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// clang-format off
+
+#include <iostream>
+
+// tag::classes[]
+#include <boost/openmethod.hpp>
+#include <boost/openmethod/initialize.hpp>
+
+struct Node {
+    virtual ~Node() {}
+    virtual int value() const = 0;
+};
+
+struct Variable : Node {
+    Variable(int value) : v(value) {}
+    int value() const override { return v; }
+    int v;
+};
+
+template<typename Op>
+struct BinaryOp : Node {
+    BinaryOp(const Node& left, const Node& right) : left(left), right(right) {}
+    int value() const override { return Op()(left.value(), right.value()); }
+    const Node& left;
+    const Node& right;
+};
+// end::classes[]
+
+using namespace boost::openmethod;
+
+// tag::method[]
+BOOST_OPENMETHOD(
+    postfix, (virtual_ptr<const Node> node, std::ostream& os), void);
+
+BOOST_OPENMETHOD_OVERRIDE(
+    postfix, (virtual_ptr<const Variable> var, std::ostream& os), void) {
+    os << var->v;
+}
+// end::method[]
+
+// tag::postfix_binary[]
+template<class BinaryOp, char Op>
+auto postfix_binary(virtual_ptr<const BinaryOp> node, std::ostream& os) {
+    postfix(node->left, os);
+    os << ' ';
+    postfix(node->right, os);
+    os << " " << Op;
+}
+// end::postfix_binary[]
+
+// tag::add_postfix_binary[]
+BOOST_OPENMETHOD_TYPE(
+    postfix, (virtual_ptr<const Node> node, std::ostream& os), void)::
+    override<
+        postfix_binary<BinaryOp<std::plus<int>>, '+'>,
+        postfix_binary<
+            BinaryOp<std::multiplies<int>>, '*'>> add_binary_overriders;
+// end::add_postfix_binary[]
+
+// tag::main[]
+BOOST_OPENMETHOD_CLASSES(
+    Node, Variable, BinaryOp<std::plus<int>>, BinaryOp<std::multiplies<int>>);
+
+auto main() -> int {
+    boost::openmethod::initialize();
+    Variable a{2}, b{3}, c{4};
+    BinaryOp<std::plus<int>> d{a, b};
+    BinaryOp<std::multiplies<int>> e{d, c};
+    postfix(e, std::cout);
+    std::cout << " = " << e.value() << "\n"; // 2 3 + 4 * = 20
+}
+// end::main[]