Akaban / coreml-vm

A basic CoreML Virtual Machine

CoreML Virtual Machine

This program is a OCaml implemented Virtual Machine capable of running simple CoreML code, it reads a .cml file as its input then feed it to the built-in compiler in order to run it with the Virtual Machine

Getting Started

• A recent version of OCaml is required
• ocaml-findlib, ocamldep and ocamlbuild are required
• ocamllex and ocaml-menhir are required
• If all requirements of the above are meet, compile the project with make
• The result binary will be named VM

Example .cml

The following CoreML code will compute the n-th Fibonacci number, the argument n is to be set in fibo_arg

let fibo_arg=10 in
let fibo_arg=ref fibo_arg in

let fibo1=ref 1 in
let fibo2=ref 1 in

while !fibo_arg > 2 do
  let tmp = !fibo2 in
  fibo_arg <- !fibo_arg - 1 ;
  fibo2 <- !fibo1 + !fibo2 ;
  fibo1 <- tmp done ;
  print !fibo2

The compiled VM program is,

10 Let(fibo_arg) Alloc Dup fibo_arg Store Let(fibo_arg) Alloc Dup 1 Store Let(fibo1) Alloc Dup 1 Store Let(fibo2) 2 fibo_arg Load > 
While {2, fibo_arg, Load, >} do 
  {fibo2, Load, Let(tmp), fibo_arg, 1, fibo_arg, Load, -, Store, (), fibo2, fibo2, Load, fibo1, Load, +, Store, (), fibo1, tmp, Store, ()} 
fibo2 Load Print

This will return the value 55.

Others example of code can be found in the folder tests. We can run some of these tests with the script runtest.sh

What is implemented?

• Integers, Pointers and Functions
• All basic binary operations (add, sub, mul, integer division, <, >, >=, <=, =)
• Booleans as integers (C-like), 1 is true and everything else is considered false. And (&&), Or (||) are also implemented
• References (pointers) with the keyword ref ie. let a = ref 10. We can then refer to a reference with a bang like this !a or set the value of a reference with the following syntax a <- !a + 1
• Conditionals (if) and loops (while, for).
• Increasing for loop syntax is for a=1 upto 10 do expr done. We can use a decreasing loop with downto instead of upto
• Concurrent programming (the implementation is basic though), with the keyword spawn fun arg. We can wait all threads to finish with the keyword wait
• Anonymous (lambdas) functions: let a = (fun b -> b + 1). If this function has a name we can refer to this function inside of itself recursively (no need for let rec just let)
• Printing integers (with print)

Command line arguments

It may be interesting to separate the normal stdout printing from the stderr printing (warnings and debug are printed in stderr) with redirections,

  usage: ./VM file.cml
--print-program Print compiled program
--no-exec Do not execute the compiled program on the VM
--print-stack After a thread ends, print its stack's last value
--debug Verbose VM mode, print each reduction step with its stack state
-help  Display this list of options
--help  Display this list of options