How to Add a New C++ Output Generator

This guide describes how to add a new C++ output generator to NIMBLE. C++ output generators are used to generate lines of C++ code from NIMBLE syntax trees.

Adding a C++ Generator

1. Add an entry to the cppOutputCalls list in genCpp_generateCpp.R. The entry should be of the form fxnName = 'cppGeneratorName', where where fxnName is the name of the DSL function to generate C++ code for, and 'cppGeneratorName' is a character string naming the new C++ generator function.

2. Create a new C++ generator function.
   • NIMBLE C++ generator functions take two arguemnts:
     1. code, a NIMBLE expression class object that has been annotated by size processing
     2. symTab, the symbolTable for the nimbleFunction method that code is being generated for.
   • C++ generator functions should return a character string that is a line of C++ code.

Commonly Used C++ Generators

NIMBLE has many C++ generator functions. We list a few below, but they can all be found in genCpp_generateCpp.R.

• cppOutputPointerDereference: used to dereference a C++ pointer object
• cppOutputTemplate: used to generate a line of code for a C++ template object
• cppOutputLiteral: used by the cppLiteral() function. The cppLiteral function takes character strings of fully written C++ code as arguments, and outputs that same code. Useful in situations where a complex / unique line of code needs to be generated, and it is simpler to type the code out manually than generate it. Some examples exist in cppDefs_nimbleList.R.