clo

Clo is a dynamically-typed programming language with garbage collection.

<comment>   := "#" [^\n]* "\n"
<intrinsic> := "." [^\s]+
<binding>   := <var> <expr>
<callee>    := <intrinsic> | <expr>
<expr>      := <int64_t-literal> | <ASCII-str-literal> | <var>
            |  lambda ( <var>* ) <expr>
            |  letrec ( <binding>* ) <expr>
            |  if <expr> <expr> <expr>
            |  { <expr>+ }  // sequenced evaluation
            |  ( <callee> <expr>* )
            |  @ <var> <expr>  // access var in closure's env (can simulate structs)

The distinguished feature of clo is serializing the program state as a string. The built-in function .forkstate returns a string encoding the current state, and when the state is resumed using .eval it starts right after the .forkstate call but with a return value of Void type. This resembles Linux's fork, Lisp's call/cc, etc. For example, the following program outputs 0, 1, 2, 2, 3 in order. Note: .eval works on both source code and serialized program state.

{
    (.putstr "0\n")
    (.putstr "1\n")
    letrec (state (.forkstate)) {
        (.putstr "2\n")
        if (.= (.type state) 0)  # if it is a void value
           (.putstr "3\n")
           (.eval state)
    }
}

See test/ for more code examples (*.clo).

dependencies

The source code of the interpreter is standard C++20 and thus can be compiled by any C++20-conforming compiler. The current Makefile and CI.py need clang++ with C++20 support (for sanitizer), make, and python3.

build and run

make -C src/ release
bin/clo <source-path>

python3 CI.py (re-)builds the interpreter and runs all tests.