Elements of Computing Systems Chapter 9

Preamble

We began by finishing the VM translator from the previous meeting:

• Implement CodeWriter#write_init and call it from bin/translator: enabling us to conditionally generate the necessary initialisation code;
• Generate assembly that uses independent labels for files and functions: to support labels across multiple files and functions;
• Support multiple files in the translator: now using the filename to scope labels.

As Chapter 9's project is to write any program of our choice in Jack, we instead chose to spend the rest of the meeting attempting to refactor the rather gnarly assembly-generating code we'd written previously:

• Refactor: introduce an AssemblyWriter and extract common operations;
• Extract AssemblyWriter#pop_register_d and #jump_to;
• Extract AssemblyWriter#define_label;
• Extract AssemblyWriter#push_value and #push_value_at;
• Extract AssemblyWriter#copy;
• Use AssemblyWriter#push_value in CodeWriter#write_push.

Thanks

Thanks to Leo for typing once again and to Geckoboard for hosting. Thanks again to Tom for his work on the vm-translator test suite which was invaluable during the exercises.