CppCon 2020 Template Metaprogramming: Type Traits Part 1 Jody Hagins jhagins@maystreet.com coachhagins@gmail.com ## CppCon 2020 Template Metaprogramming: Type Traits Introduction ## I ntended Audience Not necessarily beginner to C++, but beginner to traditional template metaprogramming techniques • Type traits part of standard library for ~10 years ## I ntended Audience • Beginner/Intermediate • Gentle Not necessarily beginner to C++, but beginner to traditional template metaprogramming techniques • Type traits part of standard library for ~10 years • Fundamentals have been in use for ~20 years ## I

Promise, Deferred) • Deliver to a queue • Callback registry (e.g. POSIX signals) Regardless of which type of interface is used, asynchronous functions by definition interact differently with their callers; action="/myform" method="POST">' ' type="text" name="message"/> ' ' type="submit" value="Submit"/> ' ' ) ) def post(self): self.set_header("Content-Type", "text/plain") self.write("You wrote " + self.get_body_argument("message")) Since the HTML form

myConstant = 42 A constant or variable must have the same type as the value you want to assign to it. However, you don't always have to write the type explicitly. Providing a value when you create a constant constant or variable lets the compiler infer its type. In the example above, the compiler infers that myVariable is an integer because its initial value is an integer. If the initial value doesn't provide provide enough information (or if there is no initial value), specify the type by writing it after the variable, separated by a colon. 1 let implicitInteger = 70 2 let implicitDouble = 70.0 3 let explicitDouble:

PropertyNotWritableException issue (SPR-11502) optimized handling of @Bean method override regression with return type narrowing on JDK 8 (SPR-11718) prevented double evaluation of method arguments in SpEL (SPR-11445) handle NoClassDefFoundError for TestExecution Listeners consistently (SPR-11347) * fixed @Bean meta-annotation detection when using ASM (SPR-10488) * provide access to SimpleTriggerFactoryBean property startTime enabled ServletTestExecutionListener by default in abstract base test classes (SPR-11340) * fixed type comparison in ReflectionHelper.]}\).]}\).]}\).]}\).]}\).]}\).]}\.]}\.]}\ * improved logging and exception

springframework.org Changes in version 2.0.1 (23.11.2006) ## General * included classes in the "test.annotation" and "test.jpa" packages (tiger mock directory) in the Spring API javadoc Package to depend on beans that in turn get advised by the same aspect * added @Order annotation support for @AspectJ style aspects, as alternative to implementing the Ordered interface * redesigned Package org.springframework.beans * fixed BeanWrapperImpl to correctly determine generic type for each key in a chain (e.g. "myMap[myKey][myInnerKey]") * introduced PatternEditor for

through a SerializedBeanFactoryReference * DefaultListableBeanFactory's getBean(name, type) attempts type conversion if necessary * DefaultListableBeanFactory allows for init methods to register further listener beans * optimized @Bean error messages for static factory methods as well as for argument * type mismatches * modified expression parsing to pass full TypeDescriptor context through to * ConversionService abstraction * added mode="proxy"/"aspectj" and proxy-target-class options to task:annotation-driven * JDBC bundle uses local ClassLoader as bean ClassLoader for "sql-error-codes.xml"

couldn't determine the type of the target bean (avoid NPE) * "scoped-proxy" tag works for non-Singleton FactoryBeans as well, leveraging the BeanFactory's improved type check * factored out TypeConverter * BeanWrapperImpl converts nested collection value (e.g. List within Map) to declared generic type, if applicable * BeanWrapperImpl's TypeMismatchException mentions the specific element that failed failed in case of a (generic) collection * BeanWrapperImpl assigns a given array directly if component type matches and no matching custom editors registered * added default editor for JDK 1.4's

Changes in version 3.0.0.GA (2009-12-16) * component scanning autodetects the new EE 6 "javax.annotation.ManagedBean" stereotype * updated JPA 2.0 support to the final spec (tested compatibility leniently ("title" and "Title"; "ISBN" and "ISBN") * bean properties of type enum array/collection can be populated with comma-separated String * removed getBeansWithAnnotation(Class FormattingConversionServiceFactoryBean setup * mvc:annotation-driven exposes default Validator and ConversionService as top-level beans * mvc:annotation-driven registers applicable HttpMessageConverters

of a certain type. The variable's type is called static type, the location's type is called dynamic type. If the static type is not the same as the dynamic type, it is a super-type or subtype of of the dynamic type. An identifier is a symbol declared as a name for a variable, type, procedure, etc. The region of the program over which a declaration applies is called the scope of the declaration mod nil not notin object of or out proc ptr raise ref return shl shr static template try tuple type using var when while xor yield Some keywords are unused; they are reserved for future developments

.21 2.2.2. Easier XML configuration.....21 2.2.3. Extensible XML authoring.....22 2.2.4. Annotation-driven configuration.....22 2.2.5. Autodetecting components in the classpath.....22 2.3. Aspect 25 2.5.1. Sensible defaulting in Spring MVC.....25 2.5.2. Portlet framework.....25 2.5.3. Annotation-based controllers.....25 2.5.4. A form tag library for Spring MVC.....25 2.5.5. Tiles 2 support as a J2EE RAR file ..... 91 3.11. Annotation-based configuration ..... 92 3.11.1. @Required ..... 92 3.11.2. @Autowired ..... 93 3.11.3. Fine-tuning annotation-based autowiring with qualifiers .