ToyVM

Bytecode VM for a simple lisp

• At the REPL, all forms are converted to bytecode, which is interpreted
• Possible to AOT compile a lisp file to bytecode
• Possible to directly interpret a bytecode file

Heavily inspired by this blogpost by Max Bernstein with the following changes:

• lambda is called fn
• recfn is for creating recursive lambdas
• define not required
• written in Clojure in a functional manner
• stackless evaluation using xodarap

Usage

Start a REPL

$ rlwrap lein do clean, run
==================
=== ToyVM REPL ===
==================

> (def dec
    (fn (x)
      (- x 1)))
nil

> (dec 43)
42

Compile to bytecode

Compile the example file:

$ cat factorial.edn
[

 (def dec
   (fn (n)
     (- n 1)))

 (def fact
   (recfn fact (n)
     (if (< n 2)
       1
       (* n (fact (dec n))))))

 (print (fact 5))

]

$ lein bcompile factorial.edn

$ cat out.edn
[[:push-const (n)]
 [:push-const
  [[:push-name -]
   [:push-name n]
   [:push-const 1]
   [:call-function 2]]]
 [:make-function 1]
 [:store-name dec]
 [:push-const fact]
 [:push-const (n)]
 [:push-const
  [[:push-name <]
   [:push-name n]
   [:push-const 2]
   [:call-function 2]
   [:relative-jump-if-true 9]
   [:push-name *]
   [:push-name n]
   [:push-name fact]
   [:push-name dec]
   [:push-name n]
   [:call-function 1]
   [:call-function 1]
   [:call-function 2]
   [:relative-jump 1]
   [:push-const 1])]
 [:make-recursive-function 1]
 [:store-name fact]
 [:push-name print]
 [:push-name fact]
 [:push-const 5]
 [:call-function 1]
 [:call-function 1]]

Run bytecode file

Interpret the compiled output:

$ lein binterpret out.edn
120

Compile and run in one go

$ lein do clean, bcompile factorial.edn, binterpret out.edn
120

License

Copyright © 2020 Divyansh Prakash

This program and the accompanying materials are made available under the terms of the Eclipse Public License 2.0 which is available at http://www.eclipse.org/legal/epl-2.0.

This Source Code may also be made available under the following Secondary Licenses when the conditions for such availability set forth in the Eclipse Public License, v. 2.0 are satisfied: GNU General Public License as published by the Free Software Foundation, either version 2 of the License, or (at your option) any later version, with the GNU Classpath Exception which is available at https://www.gnu.org/software/classpath/license.html.