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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 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_compiler_core::CodeObject to a PyRef<PyCode>

let code = $vm.ctx.new_code(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::PyResult<()> {

vm::Interpreter::without_stdlib(Default::default()).enter(run)

}

fn run(vm: &vm::VirtualMachine) -> vm::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.new_function("on", on).into(), 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 compiler::Mode::Single is passed to vm.compile)

match vm

.compile(&input, vm::compiler::Mode::Single, "<embedded>")

.map_err(|err| err.into_pyexception(vm, Some(&input)))

.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(exc) => {

vm.print_exception(exc);

}

Ok(())

}

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