scannergen-backend-cpp.md

Scanner Generator Backend: C++

This backend outputs a scanner as C++ source code. See scanner generator backends for what every generated scanner does and parser generator backend: C++ for the parser side.

It targets C++17 and is a self contained header which includes nothing beyond the standard library.

--backend-cpp-namespace sets the namespace the header declares everything in, which defaults to parser.

The scanner is Scanner and its tokens are the Token enum class. TokenSkipper wraps a scanner to drop the tokens marked for skipping; it is a template rather than an implementation of an interface, so anything offering the same members can take the place of a scanner. Lexemes are a std::string_view into the source, which therefore has to outlive them.

Example

examples/calculator/cpp/ is a calculator built on this backend. Its scanner was generated with:

golr scanner \
  --frontend golr \
  --frontend-file-path calculator.golr \
  --backend cpp \
  --backend-cpp-namespace calculator::parser \
  --backend-file-path parser/scanner.hpp