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// SPDX-FileCopyrightText: 2022 Kevin Amado <kamadorueda@gmail.com>
//
// SPDX-License-Identifier: AGPL-3.0-only
use std::collections::LinkedList;
use std::rc::Rc;
use super::runtime_stack_frame::RuntimeStackFrame;
use crate::interpreter::error::Error;
use crate::interpreter::location::Location;
use crate::interpreter::scope::ScopeKind;
use crate::interpreter::value::Value;
#[derive(Debug)]
pub(crate) struct Runtime {
pub(crate) stack: LinkedList<RuntimeStackFrame>,
}
impl Runtime {
pub(crate) fn new() -> Runtime {
Runtime { stack: LinkedList::new() }
}
fn add_stack_frame(&mut self, description: String, location: Location) {
let stack_frame = RuntimeStackFrame { description, location };
log::trace!("stack += {stack_frame}");
self.stack.push_back(stack_frame);
}
pub(crate) fn advance(
&mut self,
value: &Rc<Value>,
) -> Result<Rc<Value>, Error> {
let value = match &**value {
Value::DeferredValue { ast, path, scope } => {
Ok(Rc::new(Value::from_ast(path.clone(), ast.clone(), scope)))
}
Value::FunctionApplication {
argument_index,
arguments,
function,
location,
} => {
let function = self.advance_monotonically(function.clone())?;
match &*function {
Value::BuiltInFunction {
expected_arguments,
identifier,
} => {
self.add_stack_frame(
format!("evaluating {identifier:?}"),
location.clone(),
);
if *expected_arguments == arguments.len() {
let function = match identifier.as_str() {
"built-in +" => Runtime::built_in_addition,
_ => unreachable!(),
};
function(self, arguments.clone(), location)
} else {
Ok(value.clone())
}
}
Value::Function {
bind_to,
implementation,
path,
scope,
..
} => {
let arguments = arguments.clone();
let argument = arguments[*argument_index].clone();
let argument = self.advance_monotonically(argument)?;
self.add_stack_frame(
format!(
"calling a {:?} with argument #{} of kind {:?}",
function.kind(),
argument_index + 1,
argument.kind(),
),
location.clone(),
);
let scope = scope.derive(ScopeKind::Plain);
if let Some(bind_to) = bind_to {
scope.bind(bind_to.clone(), argument);
}
let value = Value::DeferredValue {
ast: implementation.clone(),
path: path.clone(),
scope: scope.clone(),
};
let value = if argument_index < &arguments.len() {
value
} else {
Value::FunctionApplication {
argument_index: argument_index + 1,
arguments,
function: Rc::new(value),
location: location.clone(),
}
};
let value = Rc::new(value);
let value = self.advance_monotonically(value)?;
Ok(value)
}
_ => Err(Error::Interpreter {
description: format!(
"calling a {:?} is not currently possible",
function.kind(),
),
location: location.clone(),
stack: self.stack.clone(),
}),
}
}
Value::Variable { identifier, location, scope } => {
match scope.lookup(identifier) {
Some(value) => Ok(value),
None => match identifier.as_str() {
"built-in +" => {
Ok(Rc::new(Value::FunctionApplication {
argument_index: 0,
arguments: Vec::new(),
function: Rc::new(
Value::BuiltInFunction {
expected_arguments: 2,
identifier: identifier.clone(),
},
),
location: location.clone(),
}))
}
_ => Err(Error::Interpreter {
description: format!(
"undefined variable {identifier:?}"
),
location: location.clone(),
stack: self.stack.clone(),
}),
},
}
}
_ => Ok(value.clone()),
};
log::trace!("value = {:#?}", &value);
value
}
pub(crate) fn advance_monotonically(
&mut self,
mut value: Rc<Value>,
) -> Result<Rc<Value>, Error> {
let mut old_value;
loop {
old_value = value;
value = self.advance(&old_value)?;
if Rc::ptr_eq(&value, &old_value) {
break;
}
}
Ok(value)
}
fn built_in_addition(
&mut self,
mut args: Vec<Rc<Value>>,
location: &Location,
) -> Result<Rc<Value>, Error> {
let rhs = args.remove(1);
let lhs = args.remove(0);
let lhs = self.advance_monotonically(lhs)?;
let rhs = self.advance_monotonically(rhs)?;
match (&*lhs, &*rhs) {
(Value::Int(lhs_value), Value::Int(rhs_value)) => {
match lhs_value.checked_add(*rhs_value) {
Some(value) => Ok(Rc::new(Value::Int(value))),
None => Err(Error::Interpreter {
description: format!(
"integer overflow while adding {lhs_value} and \
{rhs_value}"
),
location: location.clone(),
stack: self.stack.clone(),
}),
}
}
_ => Err(Error::Interpreter {
description: format!(
"built-in + is not implemented for operands of type {:?} \
and {:?}",
lhs.kind(),
rhs.kind(),
),
location: location.clone(),
stack: self.stack.clone(),
}),
}
}
}