Slang for Dune

Compiler Construction 2022

Computer Laboratory

University of Cambridge

Timothy G. Griffin (tgg22@cam.ac.uk)

This directory contains OCaml code implementing high-level interpreters for the language Slang (= Simple LANGuage), a fragment of the language L3 from 1B Semantics.

Extensions

My list and list pattern matching extensions to the compiler can be found in the extensions branch.

Building

Install Dune. Build the project with dune build. Install slang with dune install. Format the code with dune build @fmt and dune promote.

Usage

Usage: slang [options] [<file>]

Options are:

• -V verbose front end
• -v verbose interpreter(s)
• -c show compiled code (but don't run it)
• -i0 Interpreter 0
• -i1 Interpreter 1
• -i2 Interpreter 2
• -i3 Interpreter 3
• -i4 Jargon VM
• -all all interpreters
• -stackmax set max stack size (default = 1000)
• -heapmax set max heap size (default = 1000)
• -t run all test/*.slang with each selected interpreter, report unexpected outputs (silent otherwise)
• -help Display this list of options
• --help Display this list of options

Files

Every .ml file has an associated .mli file describing its interface.

File	Description
errors.ml	Error exception
past.ml	the Parsed AST, with pretty printing
lexer.mll	specification for ocamllex
parser.mly	specification for ocamlyacc
ast.ml	"internal" AST, with pretty printing
past_to_ast.ml	translated from parsed to internal AST
static.ml	static analysis (check types and other rules)
front_end.ml	the front end : parse, static check, translate.
free_vars.ml	free variable calculation
tests.ml	code for parsing tests/manifest.txt and setting up testing.
slang.ml	main file, implementing the command-line for the interpreter and compiler

Interpreters (In order of presentation in lectures)

File	Description
interp_0.ml	The "definitional" interpreter.
interp_2.ml	A high-level stack-oriented abstract machine with compiler.
	What do I mean by "high-level"?
	- Code is still tree-structured.
	- Complex values are pushed onto value stack.
	- Heap used only for references.
	- Code is maintained on a code stack.
	- Program variables contained in code.
interp_3.ml	A slightly lower-level stack-oriented abstract machine with compiler. Code is now in a strictly linear array of instructions. State includes a "code pointer".
jargon.ml	Could be called "interp_4". The Jargon VM and compiler Only simple values on the value stack Complex values now stored in heap Value stack items now have an address.
interp_1.ml	The "missing link" between interp_0 and interp_2. Best understood in terms of a CPS translation on interp_0 itself.