to constrain or ban standard features. In some cases we prefer a homegrown or third-party library over a library defined in the C++ Standard, either out of perceived superiority or insufficient value to recompilation when headers change. • A forward declaration may be broken by subsequent changes to the library. Forward declarations of functions and templates can prevent the header owners from making otherwise-compatible Includes Use standard order for readability and to avoid hidden dependencies: Related header, C library, C++ library, other libraries’ .h, your project’s .h. All of a project’s header files should be listed

error codes. Cons: May cause the control flow to be confusing. Easy to miss error cases when making library calls. 4 Decision: Exceptions must follow certain conditions: • Raise exceptions like this: raise Decision: Okay to use for simple cases. Each portion must fit on one line: mapping expression, for clause, filter expression. Multiple for clauses or filter expressions are not permitted. Use loops instead Lambda Functions link￿ Okay for one-liners. Definition: Lambdas define anonymous functions in an expression, as opposed to a statement. They are often used to define callbacks or operators for higher- order

BarException e) • the colon (:) in an enhanced for (“foreach”) statement • the arrow in a lambda expression: (String str) -> str.length() but not • the two colons (::) of a method reference, which is written number of cases noted below, underscores. Thus each valid identifier name is matched by the regular expression \w+ . In Google Style special prefixes or suffixes, like those seen in the examples name_ class member must be qualified, it is qualified with that class’s name, not with a reference or expression of that class’s type. Foo aFoo = ...; Foo.aStaticMethod(); // good aFoo.aStaticMethod(); // bad

File description comment, including purpose of program, inputs, and out- puts 4. source() and library() statements 5. Function definitions 6. Executed statements, if applicable (e.g., print, plot) Unit num.days, show.plot = TRUE) Ideally, unit tests should serve as sample function calls (for shared library rou- tines). Function Documentation Functions should contain a comments section immediately below