I use straightforward techniques to automatically generate about a third of my C++ code (108,000 lines of code or so). When I'm writing code, I keep an eye out for things that I'm doing which are very repetitious.
For instance, I have nine libraries which do the same things for different file formats. Ideally I'd like the main API for each library to be as similar as possible. So the files which implement the API are generated by a Perl template script. Each library implements a couple of core functions; then the code generated from the template calls those functions in various ways. So I implement LowLevelStepImport; the automatically generated code uses that to implement ArrayStepImport, ClassStepImport, CCallableStepImport, etc. Then I implement LowLevelJTImport, and it implements ArrayJtImport, ClassJTImport, CCallableStepImport, etc.
There are lots of advantages to this. It means I don't have to write a bunch of boring code which is essentially the same. It makes it very easy to keep the APIs consistent across all the libraries. If I need to change part of the API, I just change the template and all the libraries update automatically. And if I add a new library, it is trivial to get it added to the collection.
For instance, I have nine libraries which do the same things for different file formats. Ideally I'd like the main API for each library to be as similar as possible. So the files which implement the API are generated by a Perl template script. Each library implements a couple of core functions; then the code generated from the template calls those functions in various ways. So I implement LowLevelStepImport; the automatically generated code uses that to implement ArrayStepImport, ClassStepImport, CCallableStepImport, etc. Then I implement LowLevelJTImport, and it implements ArrayJtImport, ClassJTImport, CCallableStepImport, etc.
There are lots of advantages to this. It means I don't have to write a bunch of boring code which is essentially the same. It makes it very easy to keep the APIs consistent across all the libraries. If I need to change part of the API, I just change the template and all the libraries update automatically. And if I add a new library, it is trivial to get it added to the collection.