Dynamic cast constraint (#5082)

* dynamic cast constraint
* cleanup HistogramWordStringKernel

Author: gf712

src/shogun/base/AnyParameter.h

@@ -14,6 +14,7 @@
 #include <list>
 #include <memory>
 #include <string_view>
+#include <optional>
 
 namespace shogun
 {
@@ -168,7 +169,7 @@ namespace shogun
 		}
 		AnyParameter(
 		    Any&& value, const AnyParameterProperties& properties,
-		    std::function<std::string(Any)> constrain_function)
+		    std::function<std::optional<std::string>(Any)> constrain_function)
 		    : m_value(std::move(value)), m_properties(properties),
 		      m_constrain_function(std::move(constrain_function))
 		{
@@ -218,7 +219,7 @@ namespace shogun
 			return m_init_function;
 		}
 
-		const std::function<std::string(Any)>& get_constrain_function() const
+		const std::function<std::optional<std::string>(Any)>& get_constrain_function() const
 		    noexcept
 		{
 			return m_constrain_function;
@@ -272,7 +273,7 @@ namespace shogun
 		Any m_value;
 		AnyParameterProperties m_properties;
 		std::shared_ptr<params::AutoInit> m_init_function;
-		std::function<std::string(Any)> m_constrain_function;
+		std::function<std::optional<std::string>(Any)> m_constrain_function;
 		std::vector<std::function<void()>> m_callback_functions;
 	};
 } // namespace shogun

src/shogun/base/SGObject.h

@@ -921,10 +921,8 @@ class SGObject: public std::enable_shared_from_this<SGObject>
 				BaseTag(name), AnyParameter(
 						make_any_ref(value), properties,
 						[constrain_function](const auto& val) {
-							std::string result;
 							auto casted_val = any_cast<T1>(val);
-							constrain_function.run(casted_val, result);
-							return result;
+							return constrain_function.check(casted_val);
 						}));
 		register_parameter_visitor<T1>();
 	}
@@ -1131,12 +1129,12 @@ class SGObject: public std::enable_shared_from_this<SGObject>
 
 		if (pprop.has_property(ParameterProperties::CONSTRAIN))
 		{
-			auto msg = param.get_constrain_function()(make_any(value));
-			if (!msg.empty())
+			const auto& val = param.get_constrain_function()(make_any(value));
+			if (val)
 			{
 				require(!do_checks,
 					"{}::{} cannot be updated because it must be: {}!",
-					get_name(), _tag.name().c_str(), msg.c_str());
+					get_name(), _tag.name().c_str(), *val);
 			}
 		}
 		if constexpr (std::is_same_v<T, Any>)

src/shogun/base/constraint.h

@@ -7,11 +7,16 @@
 #ifndef __CONSTRAINT_H__
 #define __CONSTRAINT_H__
 
+#include <shogun/io/SGIO.h>
+#include <shogun/util/traits.h>
+
 #include <string>
 #include <tuple>
 
 namespace shogun
 {
+	class SGObject;
+
 	namespace constraint_detail
 	{
 		template <typename T, typename... Args, std::size_t... Idx>
@@ -86,18 +91,80 @@ namespace shogun
 	template <typename T>
 	struct generic_checker
 	{
-	public:
-		generic_checker(T val) : m_val(val){};
-		bool operator()(T val) const
+		generic_checker() = default;
+		bool operator()(const T& val) const
 		{
 			return check(val);
 		};
 
 		virtual std::string error_msg() const = 0;
 
+	protected:
+		virtual bool check(const T& val) const = 0;
+	};
+
+	template <typename T>
+	struct custom_constraint: generic_checker<T>
+	{
+		template <typename Functor>
+		custom_constraint(Functor&& func): m_func(func) 
+		{
+		}
+
+		std::string error_msg() const override
+		{
+			return msg;
+		}
+
+	protected:
+		bool check(const T& val) const override 
+		{
+			try
+			{
+				m_func(val);
+			}
+			catch (const std::exception& e)
+			{
+				msg = std::string(e.what());
+				return false;
+			}
+
+			return true;
+		}
+
+	private:
+		std::string msg;
+		std::function<void(const T&)> m_func;
+	};
+
+
+	template <typename DerivedType>
+	struct castable: generic_checker<std::shared_ptr<SGObject>>
+	{
+		castable(): generic_checker<std::shared_ptr<SGObject>>()
+		{
+		}
+
+		std::string error_msg() const override
+		{
+			return "of type " + demangled_type<DerivedType>();
+		}
+
+	protected:
+		bool check(const std::shared_ptr<SGObject>& ptr) const override 
+		{
+			return static_cast<bool>(std::dynamic_pointer_cast<DerivedType>(ptr));
+		}
+	};
+
+	template <typename T>
+	struct comparisson_checker: generic_checker<T>
+	{
+		comparisson_checker(T val): generic_checker<T>() {
+			m_val = val;
+		}
 	protected:
 		T m_val;
-		virtual bool check(T val) const = 0;
 	};
 
 	/**
@@ -106,18 +173,17 @@ namespace shogun
 	 * @tparam T the type of val
 	 */
 	template <typename T>
-	struct less_than : generic_checker<T>
+	struct less_than : comparisson_checker<T>
 	{
-	public:
-		less_than(T val) : generic_checker<T>(val){};
+		less_than(T val) : comparisson_checker<T>(val){};
 
 		std::string error_msg() const override
 		{
 			return "less than " + std::to_string(this->m_val);
 		}
 
 	protected:
-		bool check(T val) const override
+		bool check(const T& val) const override
 		{
 			return val < this->m_val;
 		}
@@ -129,18 +195,17 @@ namespace shogun
 	 * @tparam T the type of val
 	 */
 	template <typename T>
-	struct less_than_or_equal : generic_checker<T>
+	struct less_than_or_equal : comparisson_checker<T>
 	{
-	public:
-		less_than_or_equal(T val) : generic_checker<T>(val){};
+		less_than_or_equal(T val) : comparisson_checker<T>(val){};
 
 		std::string error_msg() const override
 		{
 			return "less than " + std::to_string(this->m_val);
 		}
 
 	protected:
-		bool check(T val) const override
+		bool check(const T& val) const override
 		{
 			return val <= this->m_val;
 		}
@@ -152,17 +217,16 @@ namespace shogun
 	 * @tparam T the type of val
 	 */
 	template <typename T>
-	struct greater_than : generic_checker<T>
+	struct greater_than : comparisson_checker<T>
 	{
-	public:
-		greater_than(T val) : generic_checker<T>(val){};
+		greater_than(T val) : comparisson_checker<T>(val){};
 		std::string error_msg() const override
 		{
 			return "greater than " + std::to_string(this->m_val);
 		}
 
 	protected:
-		bool check(T val) const override
+		bool check(const T& val) const override
 		{
 			return val > this->m_val;
 		}
@@ -174,18 +238,17 @@ namespace shogun
 	 * @tparam T the type of val
 	 */
 	template <typename T>
-	struct greater_than_or_equal : generic_checker<T>
+	struct greater_than_or_equal : comparisson_checker<T>
 	{
-	public:
-		greater_than_or_equal(T val) : generic_checker<T>(val){};
+		greater_than_or_equal(T val) : comparisson_checker<T>(val){};
 
 		std::string error_msg() const override
 		{
 			return "less than " + std::to_string(this->m_val);
 		}
 
 	protected:
-		bool check(T val) const override
+		bool check(const T& val) const override
 		{
 			return val >= this->m_val;
 		}
@@ -237,14 +300,13 @@ namespace shogun
 		}
 
 		template <typename T>
-		bool run(T val, std::string& buffer) const
+		std::optional<std::string> check(const T& val) const
 		{
 			if (!constraint_detail::apply(val, m_funcs))
 			{
-				buffer = constraint_detail::get_error(m_funcs);
-				return false;
+				return constraint_detail::get_error(m_funcs);
 			}
-			return true;
+			return std::nullopt;
 		}
 
 	private: