Replaced implicit trivial_value_is_null tag for columns with explicit tvin method

This isn't database vendor specific, but library vendor specific, as I
used this implicit behaviour quite a lot, but it is utterly confusing
when mixed with prepared statements. Explicit is better here.

include/sqlpp11/boolean.h

@@ -63,26 +63,24 @@ namespace sqlpp
 				using _value_type = boolean;
 
 				_parameter_t(const std::true_type&):
-					_trivial_value_is_null(true),
 					_value(false),
-					_is_null(_trivial_value_is_null and _is_trivial())
+					_is_null(false)
 					{}
 
 				_parameter_t(const std::false_type&):
-					_trivial_value_is_null(false),
 					_value(false),
-					_is_null(_trivial_value_is_null and _is_trivial())
+					_is_null(false)
 					{}
 
 				_parameter_t(const _cpp_value_type& value):
 					_value(value),
-					_is_null(_trivial_value_is_null and _is_trivial())
+					_is_null(false)
 					{}
 
 				_parameter_t& operator=(const _cpp_value_type& value)
 				{
 					_value = value;
-					_is_null = (_trivial_value_is_null and _is_trivial());
+					_is_null = (false);
 					return *this;
 				}
 
@@ -99,8 +97,6 @@ namespace sqlpp
 						os << value();
 					}
 
-				bool _is_trivial() const { return value() == false; }
-
 				bool is_null() const
 			 	{ 
 					return _is_null; 
@@ -120,7 +116,6 @@ namespace sqlpp
 					}
 
 			private:
-				bool _trivial_value_is_null;
 				signed char _value;
 				bool _is_null;
 			};
@@ -164,8 +159,6 @@ namespace sqlpp
 						os << value();
 					}
 
-				bool _is_trivial() const { return value() == false; }
-
 				bool is_null() const
 			 	{ 
 					if (not _is_valid)

include/sqlpp11/column.h

@@ -75,7 +75,7 @@ namespace sqlpp
 			-> typename std::enable_if<not std::is_same<column_t, typename std::decay<T>::type>::value, 
 			     assignment_t<column_t, typename _value_type::template _constraint<T>::type>>::type
 			{
-				return { *this, std::forward<T>(t) };
+				return { *this, {std::forward<T>(t)} };
 			}
 	};
 

include/sqlpp11/detail/basic_operators.h

@@ -155,8 +155,6 @@ namespace sqlpp
 					static_assert(not is_multi_expression_t<Base>::value, "multi-expression cannot have a name");
 					return { *static_cast<const Base*>(this) };
 				}
-
-			constexpr bool _is_trivial() const { return false; }
 		};
 	}
 

include/sqlpp11/expression.h

@@ -31,6 +31,7 @@
 #include <sqlpp11/boolean.h>
 #include <sqlpp11/noop.h>
 #include <sqlpp11/expression_fwd.h>
+#include <sqlpp11/tvin.h>
 #include <sqlpp11/interpreter.h>
 #include <sqlpp11/detail/wrap_operand.h>
 #include <sqlpp11/detail/serialize_tuple.h>
@@ -42,10 +43,22 @@ namespace sqlpp
 		{
 			using _is_assignment = std::true_type;
 			using column_type = Lhs;
-			using value_type = Rhs;
+			using value_type = tvin_wrap_t<Rhs>;
+			// FIXME: Need parameter_tuple back
+
+			assignment_t(Lhs lhs, Rhs rhs):
+				_lhs(lhs), 
+				_rhs(rhs)
+			{}
+
+			assignment_t(const assignment_t&) = default;
+			assignment_t(assignment_t&&) = default;
+			assignment_t& operator=(const assignment_t&) = default;
+			assignment_t& operator=(assignment_t&&) = default;
+			~assignment_t() = default;
 
 			Lhs _lhs;
-			Rhs _rhs;
+			tvin_wrap_t<Rhs> _rhs;
 		};
 
 	template<typename Context, typename Lhs, typename Rhs>
@@ -56,7 +69,7 @@ namespace sqlpp
 			static Context& _(const T& t, Context& context)
 			{
 				interpret(t._lhs, context);
-				if (trivial_value_is_null_t<Lhs>::value and t._rhs._is_trivial())
+				if (t._rhs._is_trivial())
 				{
 					context << "=NULL";
 				}
@@ -87,7 +100,7 @@ namespace sqlpp
 		~equal_t() = default;
 
 		Lhs _lhs;
-		Rhs _rhs;
+		tvin_wrap_t<Rhs> _rhs;
 	};
 
 	template<typename Context, typename Lhs, typename Rhs>
@@ -99,9 +112,9 @@ namespace sqlpp
 			{
 				context << "(";
 				interpret(t._lhs, context);
-				if (trivial_value_is_null_t<Lhs>::value and t._rhs._is_trivial())
+				if (t._rhs._is_trivial())
 				{
-					context << "IS NULL";
+					context << " IS NULL";
 				}
 				else
 				{
@@ -130,7 +143,7 @@ namespace sqlpp
 		~not_equal_t() = default;
 
 		Lhs _lhs;
-		Rhs _rhs;
+		tvin_wrap_t<Rhs> _rhs;
 	};
 
 	template<typename Context, typename Lhs, typename Rhs>
@@ -142,9 +155,9 @@ namespace sqlpp
 			{
 				context << "(";
 				interpret(t._lhs, context);
-				if (trivial_value_is_null_t<Lhs>::value and t._rhs._is_trivial())
+				if (t._rhs._is_trivial())
 				{
-					context << "IS NOT NULL";
+					context << " IS NOT NULL";
 				}
 				else
 				{
@@ -182,16 +195,8 @@ namespace sqlpp
 			static Context& _(const T& t, Context& context)
 			{
 				context << "(";
-				if (trivial_value_is_null_t<Lhs>::value and t._lhs._is_trivial())
-				{
-					interpret(t._lhs, context);
-					context << "IS NULL";
-				}
-				else
-				{
 				context << "NOT ";
 				interpret(t._lhs, context);
-				}
 				context << ")";
 				return context;
 			}

include/sqlpp11/floating_point.h

@@ -52,27 +52,20 @@ namespace sqlpp
 			{
 				using _value_type = integral;
 
-				_parameter_t(const std::true_type&):
+				_parameter_t():
-					_trivial_value_is_null(true),
 					_value(0),
-					_is_null(_trivial_value_is_null	and _is_trivial())
+					_is_null(false)
-					{}
-
-				_parameter_t(const std::false_type&):
-					_trivial_value_is_null(false),
-					_value(0),
-					_is_null(_trivial_value_is_null	and _is_trivial())
 					{}
 
 				_parameter_t(const _cpp_value_type& value):
 					_value(value),
-					_is_null(_trivial_value_is_null and _is_trivial())
+					_is_null(false)
 					{}
 
 				_parameter_t& operator=(const _cpp_value_type& value)
 				{
 					_value = value;
-					_is_null = (_trivial_value_is_null and _is_trivial());
+					_is_null = false;
 					return *this;
 				}
 
@@ -89,8 +82,6 @@ namespace sqlpp
 						os << value();
 					}
 
-				bool _is_trivial() const { return value() == 0; }
-
 				bool is_null() const
 			 	{ 
 					return _is_null; 
@@ -110,7 +101,6 @@ namespace sqlpp
 					}
 
 			private:
-				bool _trivial_value_is_null;
 				_cpp_value_type _value;
 				bool _is_null;
 			};
@@ -156,8 +146,6 @@ namespace sqlpp
 						os << value();
 					}
 
-				bool _is_trivial() const { return value() == 0; }
-
 				bool is_null() const
 			 	{ 
 					if (not _is_valid)

include/sqlpp11/having.h

@@ -48,7 +48,6 @@ namespace sqlpp
 			static_assert(_valid_expressions::size::value == sizeof...(Expr), "at least one argument is not an expression in having()");
 
 			using _parameter_list_t = typename make_parameter_list_t<_parameter_tuple_t>::type;
-			static_assert(not _parameter_list_t::_contains_trivial_value_is_null_t::value, "must not use trivial_value_is_null in parameters of having expression, use where_parameter() instead of parameter() to turn off automatic conversion");
 
 			template<typename E>
 				void add(E&& expr)

include/sqlpp11/integral.h

@@ -52,26 +52,24 @@ namespace sqlpp
 				using _value_type = integral;
 
 				_parameter_t(const std::true_type&):
-					_trivial_value_is_null(true),
 					_value(0),
-					_is_null(_trivial_value_is_null	and _is_trivial())
+					_is_null(false)
 					{}
 
 				_parameter_t(const std::false_type&):
-					_trivial_value_is_null(false),
 					_value(0),
-					_is_null(_trivial_value_is_null	and _is_trivial())
+					_is_null(false)
 					{}
 
 				explicit _parameter_t(const _cpp_value_type& value):
 					_value(value),
-					_is_null(_trivial_value_is_null and _is_trivial())
+					_is_null(false)
 					{}
 
 				_parameter_t& operator=(const _cpp_value_type& value)
 				{
 					_value = value;
-					_is_null = (_trivial_value_is_null and _is_trivial());
+					_is_null = false;
 					return *this;
 				}
 
@@ -87,8 +85,6 @@ namespace sqlpp
 						os << value();
 					}
 
-				bool _is_trivial() const { return value() == 0; }
-
 				bool is_null() const
 			 	{ 
 					return _is_null; 
@@ -108,7 +104,6 @@ namespace sqlpp
 					}
 
 			private:
-				bool _trivial_value_is_null;
 				_cpp_value_type _value;
 				bool _is_null;
 			};
@@ -154,8 +149,6 @@ namespace sqlpp
 						os << value();
 					}
 
-				bool _is_trivial() const { return value() == 0; }
-
 				bool is_null() const
 			 	{ 
 					if (not _is_valid)

include/sqlpp11/limit.h

@@ -50,7 +50,7 @@ namespace sqlpp
 
 			static Context& _(const T& t, Context& context)
 			{
-				context << "LIMIT " << t._limit;
+				context << " LIMIT " << t._limit;
 				return context;
 			}
 		};

include/sqlpp11/offset.h

@@ -50,7 +50,7 @@ namespace sqlpp
 
 			static Context& _(const T& t, Context& context)
 			{
-				context << "OFFSET " << t._offset;
+				context << " OFFSET " << t._offset;
 				return context;
 			}
 		};

include/sqlpp11/parameter.h

@@ -33,16 +33,13 @@
 
 namespace sqlpp
 {
-	template<typename ValueType, typename NameType, typename TrivialValueIsNull>
+	template<typename ValueType, typename NameType>
-	struct parameter_t: public ValueType::template operators<parameter_t<ValueType, NameType, TrivialValueIsNull>>
+	struct parameter_t: public ValueType::template operators<parameter_t<ValueType, NameType>>
 	{
 		using _value_type = ValueType;
 		using _is_parameter = std::true_type;
 		using _is_expression_t = std::true_type;
 		using _instance_t = typename NameType::_name_t::template _member_t<typename ValueType::_parameter_t>;
-		using _trivial_value_is_null_t = TrivialValueIsNull;
-
-		static_assert(std::is_same<_trivial_value_is_null_t, std::true_type>::value or std::is_same<_trivial_value_is_null_t, std::false_type>::value, "Invalid template parameter TrivialValueIsNull");
 
 		parameter_t()
 		{}
@@ -52,17 +49,12 @@ namespace sqlpp
 		parameter_t& operator=(const parameter_t&) = default;
 		parameter_t& operator=(parameter_t&&) = default;
 		~parameter_t() = default;
-
-		constexpr bool _is_trivial() const
-		{
-			return false;
-		}
 	};
 
-	template<typename Context, typename ValueType, typename NameType, typename TrivialValueIsNull>
+	template<typename Context, typename ValueType, typename NameType>
-		struct interpreter_t<Context, parameter_t<ValueType, NameType, TrivialValueIsNull>>
+		struct interpreter_t<Context, parameter_t<ValueType, NameType>>
 		{
-			using T = parameter_t<ValueType, NameType, TrivialValueIsNull>;
+			using T = parameter_t<ValueType, NameType>;
 
 			static Context& _(const T& t, Context& context)
 			{
@@ -71,16 +63,9 @@ namespace sqlpp
 			}
 		};
 
-	template<typename NamedExpr, typename TrivialValueIsNull = trivial_value_is_null_t<typename std::decay<NamedExpr>::type>>
-		auto parameter(NamedExpr&& namedExpr)
-		-> parameter_t<typename std::decay<NamedExpr>::type::_value_type, typename std::decay<NamedExpr>::type, TrivialValueIsNull>
-		{
-			return {};
-		}
-
 	template<typename NamedExpr>
-		auto where_parameter(NamedExpr&& namedExpr)
+		auto parameter(NamedExpr&& namedExpr)
-		-> parameter_t<typename std::decay<NamedExpr>::type::_value_type, typename std::decay<NamedExpr>::type, std::false_type>
+		-> parameter_t<typename std::decay<NamedExpr>::type::_value_type, typename std::decay<NamedExpr>::type>
 		{
 			return {};
 		}

include/sqlpp11/parameter_list.h

@@ -62,10 +62,8 @@ namespace sqlpp
 		{
 			using _member_tuple_t = std::tuple<typename Parameter::_instance_t...>;
 			using size = std::integral_constant<std::size_t, sizeof...(Parameter)>;
-			using _contains_trivial_value_is_null_t = detail::or_t<typename Parameter::_trivial_value_is_null_t...>;
 
-			parameter_list_t():
+			parameter_list_t()
-				Parameter::_instance_t({typename Parameter::_trivial_value_is_null_t()})...
 			{}
 
 			template<typename Target>

include/sqlpp11/text.h

@@ -52,26 +52,24 @@ namespace sqlpp
 				using _value_type = integral;
 
 				_parameter_t(const std::true_type&):
-					_trivial_value_is_null(true),
 					_value(""),
-					_is_null(_trivial_value_is_null and _is_trivial())
+					_is_null(false)
 					{}
 
 				_parameter_t(const std::false_type&):
-					_trivial_value_is_null(false),
 					_value(""),
-					_is_null(_trivial_value_is_null and _is_trivial())
+					_is_null(false)
 					{}
 
 				_parameter_t(const _cpp_value_type& value):
 					_value(value),
-					_is_null(_trivial_value_is_null and _is_trivial())
+					_is_null(false)
 					{}
 
 				_parameter_t& operator=(const _cpp_value_type& value)
 				{
 					_value = value;
-					_is_null = (_trivial_value_is_null and _is_trivial());
+					_is_null = false;
 					return *this;
 				}
 
@@ -88,8 +86,6 @@ namespace sqlpp
 						os << value();
 					}
 
-				bool _is_trivial() const { return value() == ""; }
-
 				bool is_null() const
 			 	{ 
 					return _is_null; 
@@ -109,7 +105,6 @@ namespace sqlpp
 					}
 
 			private:
-				bool _trivial_value_is_null;
 				_cpp_value_type _value;
 				bool _is_null;
 			};
@@ -153,8 +148,6 @@ namespace sqlpp
 						os << value();
 					}
 
-				bool _is_trivial() const { return _len == 0; }
-
 				bool operator==(const _cpp_value_type& rhs) const { return value() == rhs; }
 				bool operator!=(const _cpp_value_type& rhs) const { return not operator==(rhs); }
 

include/sqlpp11/tvin.h

@@ -0,0 +1,135 @@
+/*
+ * Copyright (c) 2013, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ * 
+ *   Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ * 
+ *   Redistributions in binary form must reproduce the above copyright notice, this
+ *   list of conditions and the following disclaimer in the documentation and/or
+ *   other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef SQLPP_TVIN_H
+#define SQLPP_TVIN_H
+
+// TVIN: Trivial value is NULL
+
+#include <sqlpp11/type_traits.h>
+#include <sqlpp11/interpreter.h>
+
+namespace sqlpp
+{
+	template<typename T>
+		struct tvin_t
+		{
+			using _wrapped_t = typename wrap_operand<T>::type;
+			static_assert(not std::is_same<_wrapped_t, T>::value, "tvin() used with invalid type (only string and primitive types allowed)");
+			using _value_type = typename _wrapped_t::_value_type;
+
+			tvin_t(T t): 
+				_value({t})
+			{}
+			tvin_t(const tvin_t&) = default;
+			tvin_t(tvin_t&&) = default;
+			tvin_t& operator=(const tvin_t&) = default;
+			tvin_t& operator=(tvin_t&&) = default;
+			~tvin_t() = default;
+
+			_wrapped_t _value;
+		};
+
+	template<typename Context, typename Type>
+		struct interpreter_t<Context, tvin_t<Type>>
+		{
+			using T = tvin_t<Type>;
+
+			static void _(const T& t, Context& context)
+			{
+				static_assert(detail::wrong<T>::value, "tvin() must not be used with anything but =, ==, != and !");
+			}
+		};
+
+	template<typename T>
+		struct tvin_wrap_t
+		{
+			static constexpr bool _is_trivial()
+			{
+				return false;
+			}
+
+			tvin_wrap_t(T t): 
+				_value(t)
+			{}
+			tvin_wrap_t(const tvin_wrap_t&) = default;
+			tvin_wrap_t(tvin_wrap_t&&) = default;
+			tvin_wrap_t& operator=(const tvin_wrap_t&) = default;
+			tvin_wrap_t& operator=(tvin_wrap_t&&) = default;
+			~tvin_wrap_t() = default;
+
+			T _value;
+		};
+
+	template<typename T>
+		struct tvin_wrap_t<tvin_t<T>>
+		{
+			bool _is_trivial() const
+			{
+				return _value._is_trivial();
+			};
+
+			tvin_wrap_t(tvin_t<T> t): 
+				_value(t._value)
+			{}
+			tvin_wrap_t(const tvin_wrap_t&) = default;
+			tvin_wrap_t(tvin_wrap_t&&) = default;
+			tvin_wrap_t& operator=(const tvin_wrap_t&) = default;
+			tvin_wrap_t& operator=(tvin_wrap_t&&) = default;
+			~tvin_wrap_t() = default;
+
+			typename tvin_t<T>::_wrapped_t _value;
+		};
+
+	template<typename Context, typename Type>
+		struct interpreter_t<Context, tvin_wrap_t<Type>>
+		{
+			using T = tvin_wrap_t<Type>;
+
+			static Context& _(const T& t, Context& context)
+			{
+				if (t._is_trivial())
+				{
+					context << "NULL";
+				}
+				else
+				{
+					interpret(t._value, context);
+				}
+				return context;
+			}
+		};
+
+
+	template<typename T>
+	auto tvin(T t) -> tvin_t<typename std::decay<T>::type>
+	{
+		return {t};
+	}
+
+}
+
+#endif

include/sqlpp11/type_traits.h

@@ -92,7 +92,6 @@ namespace sqlpp
 	SQLPP_IS_COLUMN_TRAIT_GENERATOR(must_not_update);
 	SQLPP_IS_COLUMN_TRAIT_GENERATOR(require_insert);
 	SQLPP_IS_COLUMN_TRAIT_GENERATOR(can_be_null);
-	SQLPP_IS_COLUMN_TRAIT_GENERATOR(trivial_value_is_null);
 
 	SQLPP_TYPE_TRAIT_GENERATOR(is_table);
 	SQLPP_TYPE_TRAIT_GENERATOR(is_select);

include/sqlpp11/where.h

@@ -50,7 +50,6 @@ namespace sqlpp
 			static_assert(_valid_expressions::size::value == sizeof...(Expr), "at least one argument is not an expression in where()");
 
 			using _parameter_list_t = typename make_parameter_list_t<_parameter_tuple_t>::type;
-			static_assert(not _parameter_list_t::_contains_trivial_value_is_null_t::value, "must not use trivial_value_is_null in parameters of where expression, use where_parameter() instead of parameter() to turn off automatic conversion");
 
 			template<typename E>
 				void add(E&& expr)

tests/InterpretTest.cpp

@@ -40,7 +40,12 @@ int main()
 	TabSample t;
 
 	interpret(t.alpha, printer).flush();
-	interpret(t.alpha = 7, printer).flush();
+	interpret(t.alpha = 0, printer).flush();
+	interpret(t.alpha = sqlpp::tvin(0), printer).flush();
+	interpret(t.alpha == 0, printer).flush();
+	interpret(t.alpha == sqlpp::tvin(0), printer).flush();
+	interpret(t.alpha != 0, printer).flush();
+	interpret(t.gamma != sqlpp::tvin(false), printer).flush();
 	interpret(t.alpha == 7, printer).flush();
 	interpret(t.beta + "kaesekuchen", printer).flush();
 
@@ -58,6 +63,7 @@ int main()
 	interpret(insert_into(t), printer).flush();
 	interpret(insert_into(t).default_values(), printer).flush();
 	interpret(insert_into(t).set(t.gamma = true), printer).flush();
+	interpret(insert_into(t).set(t.gamma = sqlpp::tvin(false)), printer).flush();
 
 	return 0;
 }