03_Modularity.md

3. Modularity

3.1 Implementation

• To distinguish between interface and implementation, we have function declarations and definitions
• These are kept in different places

3.2 Separate Compilation

• User code only sees declarations
• The definitions are in separate files and also compiled separately
• This enforces strict separation
• Header files (.h) for declarations
• Implementation in .cpp files which include the header file

3.3 Namespaces

• Namespaces group declarations that belong together
• Avoids name clashes
• namespace X { … }
• X::…
• Standard library uses the std namespace
• To make everything from a namespace directly accessible: using namespace std;
• using in header files is bad style

3.4 Error Handling

• throw exception(message)
• try { … } catch(exception) { … }
• <stdexcept> defines some exceptions, e.g. out_of_range, length_error
• Functions that never throw can be declared noexcept, e.g. void fn () noexcept { … }
• To rethrow the same exception, just throw can be used
• Exceptions report errors at run time, asserts can also report during compile time
• static_assert(4 <= sizeof(int), msg)
• static_assert can be used for everything that is expressed using constant expressions. It is often used for checking types of parameters in generic programming