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PartIIProject

Cambridge Part II Project.

The end-result is the dissertation, which is what I got marked on.

Also see glossary.md

Front-end

The entry point to the parser is SchemeParser.java To understand the parser, have a look at SchemeFile.g4, it includes the other parts of the grammar, and uses parser actions to construct abstract syntax trees. The abstract syntax tree objects are under src/main/java/rmk35/partIIProject/runtime as the AST is exposed in Scheme to the runtime

Back-end

This is organised into OutputClasses (subclasses: inner and main class), which contain ByteCodeMethods which contain a list of instructions. The ByteCodeMethod is populated by the Statements, with contain Instructions, by sending a generateOutput message (method call) to the Statement class (one begin statement that encapsulates the whole programme). There are three ways of doing tail calls, not doing them, using trampolines or maintaining our own stack. These are each subclasses of src/**/backend/statements/TailCallSettings. Briefly these work by

no tail calls trampolines own stack
method call: java method call return a call value return a call value
continuation: do nothing spawn a trampoline create a new frame

Middle

This connects the front and the back end by converting the data structures, The entry point is the LibraryOrProgramme.java file, which uses both visitors and macro matching to generate the output a visitor pattern to walk the output of the front end. Keywords are not reserved so we need to know if for example 'lambda' is syntactic or an identifier (and indeed if is syntactic, is it the inbuilt lambda one or some other macro), hence why we only get such simple output from the front-end

Runtime

The AST/runtime objects (mainly the *Value objects). ValueHelper contains code to convert Java values to Scheme values

Experiments

This folder contains things that I found unsufficiently documented so I had a look for myself.

Settings

The settings to the compiler are passed in via environment variables, the ones in use are

  • "tailcalls"
  • 0: No tail calls
  • 1: Trampolining
  • 2: Use custom stack for Scheme calls (for call/cc)
  • "intermediate"
  • When set, generates intermediate Jasmin assembly files
  • "profile"
  • When set, outputs simple profiling data
  • timeStages
  • When set, outputs time spent in front, middle (macros, mainly) and back-end stages