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mini_repl.rs
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84 lines (72 loc) · 2.96 KB
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///! This example show cases a very simple REPL.
///! While a much better REPL can be found in ../src/shell,
///! This much smaller REPL is still a useful example because it showcases inserting
///! values and functions into the Python runtime's scope, and showcases use
///! of the compilation mode "Single".
use rustpython_vm as vm;
// these are needed for special memory shenanigans to let us share a variable with Python and Rust
use std::sync::atomic::{AtomicBool, Ordering};
// this needs to be in scope in order to insert things into scope.globals
use vm::pyobject::ItemProtocol;
// This has to be a macro because it uses the py_compile macro,
// which compiles python source to optimized bytecode at compile time, so that
// the program you're embedding this into doesn't take longer to start up.
macro_rules! add_python_function {
( $scope:ident, $vm:ident, $src:literal $(,)? ) => {{
// compile the code to bytecode
let code = vm::py_compile!(source = $src);
// convert the rustpython_bytecode::CodeObject to a PyCodeRef
let code = $vm.new_code_object(code);
// run the python code in the scope to store the function
$vm.run_code_obj(code, $scope.clone())
}};
}
static ON: AtomicBool = AtomicBool::new(true);
fn on(b: bool) {
ON.store(b, Ordering::Relaxed);
}
fn main() -> vm::pyobject::PyResult<()> {
vm::Interpreter::default().enter(run)
}
fn run(vm: &vm::VirtualMachine) -> vm::pyobject::PyResult<()> {
let mut input = String::with_capacity(50);
let stdin = std::io::stdin();
let scope: vm::scope::Scope = vm.new_scope_with_builtins();
// typing `quit()` is too long, let's make `on(False)` work instead.
scope.globals.set_item("on", vm.ctx.new_function(on), vm)?;
// let's include a fibonacci function, but let's be lazy and write it in Python
add_python_function!(
scope,
vm,
// a fun line to test this with is
// ''.join( l * fib(i) for i, l in enumerate('supercalifragilistic') )
r#"\
def fib(n):
return n if n <= 1 else fib(n - 1) + fib(n - 2)
"#
)?;
while ON.load(Ordering::Relaxed) {
input.clear();
stdin
.read_line(&mut input)
.expect("Failed to read line of input");
// this line also automatically prints the output
// (note that this is only the case when compile::Mode::Single is passed to vm.compile)
match vm
.compile(&input, vm::compile::Mode::Single, "<embedded>".to_owned())
.map_err(|err| vm.new_syntax_error(&err))
.and_then(|code_obj| vm.run_code_obj(code_obj, scope.clone()))
{
Ok(output) => {
// store the last value in the "last" variable
if !vm.is_none(&output) {
scope.globals.set_item("last", output, vm)?;
}
}
Err(e) => {
vm::exceptions::print_exception(vm, e);
}
}
}
Ok(())
}