Made a bunch of compile errors easier to read

Fixed a few bugs in the process, too.
Probably also created a few, need better checks for resulting
statements.

include/sqlpp11/basic_expression_operators.h

@@ -0,0 +1,156 @@
+/*
+ * 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_DETAIL_BASIC_EXPRESSION_OPERATORS_H
+#define SQLPP_DETAIL_BASIC_EXPRESSION_OPERATORS_H
+
+#include <sqlpp11/alias.h>
+#include <sqlpp11/sort_order.h>
+#include <sqlpp11/vendor/expression_fwd.h>
+#include <sqlpp11/vendor/in_fwd.h>
+#include <sqlpp11/vendor/is_null_fwd.h>
+#include <sqlpp11/detail/logic.h>
+
+namespace sqlpp
+{
+
+	namespace detail
+	{
+		struct boolean;
+	}
+
+	// basic operators
+	template<typename Base, template<typename> class IsCorrectValueType>
+		struct basic_expression_operators
+		{
+			template<typename T>
+				struct _is_valid_comparison_operand
+			{
+				static constexpr bool value = 
+					(is_expression_t<T>::value // expressions are OK
+					or is_multi_expression_t<T>::value) // multi-expressions like ANY are OK for comparisons, too
+					and IsCorrectValueType<T>::value // the correct value type is required, of course
+					;
+			};
+
+			template<typename T>
+				vendor::equal_to_t<Base, vendor::wrap_operand_t<T>> operator==(T t) const
+				{
+					using rhs = vendor::wrap_operand_t<T>;
+					static_assert(_is_valid_comparison_operand<rhs>::value, "invalid rhs operand in comparison");
+
+					return { *static_cast<const Base*>(this), rhs{t} };
+				}
+
+			template<typename T>
+				vendor::not_equal_to_t<Base, vendor::wrap_operand_t<T>> operator!=(T t) const
+				{
+					using rhs = vendor::wrap_operand_t<T>;
+					static_assert(_is_valid_comparison_operand<rhs>::value, "invalid rhs operand in comparison");
+
+					return { *static_cast<const Base*>(this), rhs{t} };
+				}
+
+			template<typename T>
+				vendor::less_than_t<Base, vendor::wrap_operand_t<T>> operator<(T t) const
+				{
+					using rhs = vendor::wrap_operand_t<T>;
+					static_assert(_is_valid_comparison_operand<rhs>::value, "invalid rhs operand in comparison");
+
+					return { *static_cast<const Base*>(this), rhs{t} };
+				}
+
+			template<typename T>
+				vendor::less_equal_t<Base, vendor::wrap_operand_t<T>> operator<=(T t) const
+				{
+					using rhs = vendor::wrap_operand_t<T>;
+					static_assert(_is_valid_comparison_operand<rhs>::value, "invalid rhs operand in comparison");
+
+					return { *static_cast<const Base*>(this), rhs{t} };
+				}
+
+			template<typename T>
+				vendor::greater_than_t<Base, vendor::wrap_operand_t<T>> operator>(T t) const
+				{
+					using rhs = vendor::wrap_operand_t<T>;
+					static_assert(_is_valid_comparison_operand<rhs>::value, "invalid rhs operand in comparison");
+
+					return { *static_cast<const Base*>(this), rhs{t} };
+				}
+
+			template<typename T>
+				vendor::greater_equal_t<Base, vendor::wrap_operand_t<T>> operator>=(T t) const
+				{
+					using rhs = vendor::wrap_operand_t<T>;
+					static_assert(_is_valid_comparison_operand<rhs>::value, "invalid rhs operand in comparison");
+
+					return { *static_cast<const Base*>(this), rhs{t} };
+				}
+
+			vendor::is_null_t<true, Base> is_null() const
+			{
+				return { *static_cast<const Base*>(this) };
+			}
+
+			vendor::is_null_t<false, Base> is_not_null() const
+			{
+				return { *static_cast<const Base*>(this) };
+			}
+
+			sort_order_t<Base, sort_type::asc> asc()
+			{ 
+				return { *static_cast<const Base*>(this) };
+			}
+
+			sort_order_t<Base, sort_type::desc> desc()
+			{ 
+				return { *static_cast<const Base*>(this) };
+			}
+
+			// Hint: use value_list wrapper for containers...
+			template<typename... T>
+				vendor::in_t<true, Base, vendor::wrap_operand_t<T>...> in(T... t) const
+				{
+					static_assert(detail::all_t<_is_valid_comparison_operand, vendor::wrap_operand_t<T>...>::value, "at least one operand of in() is not valid");
+					return { *static_cast<const Base*>(this), vendor::wrap_operand_t<T>{t}... };
+				}
+
+			template<typename... T>
+				vendor::in_t<false, Base, vendor::wrap_operand_t<T>...> not_in(T... t) const
+				{
+					static_assert(detail::all_t<_is_valid_comparison_operand, vendor::wrap_operand_t<T>...>::value, "at least one operand of in() is not valid");
+					return { *static_cast<const Base*>(this), vendor::wrap_operand_t<T>{t}... };
+				}
+
+			template<typename alias_provider>
+				expression_alias_t<Base, alias_provider> as(const alias_provider&)
+				{
+					return { *static_cast<const Base*>(this) };
+				}
+		};
+
+}
+#endif