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//! [`Environment`] and other types related to [`Value`] collections.
use core::{iter, ops};
pub use self::variable_map::{Assertions, Comparisons, Prelude};
use crate::{
alloc::{hash_map, Arc, HashMap, String, ToOwned},
arith::{OrdArithmetic, StdArithmetic},
exec::Operations,
fns, NativeFn, Value,
};
mod variable_map;
/// Environment containing named `Value`s.
///
/// Note that the environment implements the [`Index`](ops::Index) trait, which allows to eloquently
/// access or modify environment. Similarly, [`IntoIterator`] / [`Extend`] traits
/// allow to construct environments.
///
/// # Examples
///
/// ```
/// use arithmetic_eval::{env::{Comparisons, Prelude}, Environment, Value};
///
/// // Load environment from the standard containers.
/// let mut env = Environment::<f64>::new();
/// env.extend(Prelude::iter().chain(Comparisons::iter()));
/// // Add a custom variable for a good measure.
/// env.insert("x", Value::Prim(1.0));
///
/// assert_eq!(env["true"], Value::Bool(true));
/// assert_eq!(env["x"], Value::Prim(1.0));
/// for (name, value) in &env {
/// println!("{name} -> {value:?}");
/// }
///
/// // It's possible to base an environment on other env, as well.
/// let mut other_env = Environment::new();
/// other_env.extend(
/// env.into_iter().filter(|(_, val)| val.is_function()),
/// );
/// assert!(other_env.get("x").is_none());
/// ```
#[derive(Debug, Clone)]
pub struct Environment<T> {
variables: HashMap<String, Value<T>>,
arithmetic: Arc<dyn OrdArithmetic<T>>,
}
impl<T> Default for Environment<T>
where
StdArithmetic: OrdArithmetic<T>,
{
fn default() -> Self {
Self::new()
}
}
/// Compares environments by variables; arithmetics are ignored.
impl<T: PartialEq> PartialEq for Environment<T> {
fn eq(&self, other: &Self) -> bool {
self.variables == other.variables
}
}
impl<T> Environment<T>
where
StdArithmetic: OrdArithmetic<T>,
{
/// Creates a new environment.
pub fn new() -> Self {
Self {
variables: HashMap::new(),
arithmetic: Arc::new(StdArithmetic),
}
}
}
impl<T> Environment<T> {
/// Creates an environment with the specified arithmetic.
pub fn with_arithmetic<A>(arithmetic: A) -> Self
where
A: OrdArithmetic<T> + 'static,
{
Self {
variables: HashMap::new(),
arithmetic: Arc::new(arithmetic),
}
}
pub(crate) fn operations(&self) -> Operations<'_, T> {
Operations::from(&*self.arithmetic)
}
/// Gets a variable by name.
pub fn get(&self, name: &str) -> Option<&Value<T>> {
self.variables.get(name)
}
/// Checks if this environment contains a variable with the specified name.
pub fn contains(&self, name: &str) -> bool {
self.variables.contains_key(name)
}
/// Iterates over variables.
pub fn iter(&self) -> impl Iterator<Item = (&str, &Value<T>)> + '_ {
self.variables
.iter()
.map(|(name, value)| (name.as_str(), value))
}
/// Inserts a variable with the specified name.
pub fn insert(&mut self, name: &str, value: Value<T>) -> &mut Self {
self.variables.insert(name.to_owned(), value);
self
}
/// Inserts a native function with the specified name.
pub fn insert_native_fn(
&mut self,
name: &str,
native_fn: impl NativeFn<T> + 'static,
) -> &mut Self {
self.insert(name, Value::native_fn(native_fn))
}
/// Inserts a [wrapped function](fns::FnWrapper) with the specified name.
///
/// Calling this method is equivalent to [`wrap`](fns::wrap)ping a function and calling
/// [`insert_native_fn()`](Self::insert_native_fn) on it. Thanks to type inference magic,
/// the Rust compiler will usually be able to extract the `Args` type param
/// from the function definition, provided that type of function arguments and its return type
/// are defined explicitly or can be unequivocally inferred from the declaration.
pub fn insert_wrapped_fn<const CTX: bool, Args, F>(
&mut self,
name: &str,
fn_to_wrap: F,
) -> &mut Self
where
fns::FnWrapper<Args, F, CTX>: NativeFn<T> + 'static,
{
let wrapped = fns::wrap::<CTX, Args, _>(fn_to_wrap);
self.insert(name, Value::native_fn(wrapped))
}
}
impl<T> ops::Index<&str> for Environment<T> {
type Output = Value<T>;
fn index(&self, index: &str) -> &Self::Output {
self.get(index)
.unwrap_or_else(|| panic!("Variable `{index}` is not defined"))
}
}
impl<T> IntoIterator for Environment<T> {
type Item = (String, Value<T>);
type IntoIter = IntoIter<T>;
fn into_iter(self) -> Self::IntoIter {
IntoIter {
inner: self.variables.into_iter(),
}
}
}
/// Result of converting `Environment` into an iterator.
#[derive(Debug)]
pub struct IntoIter<T> {
inner: hash_map::IntoIter<String, Value<T>>,
}
impl<T> Iterator for IntoIter<T> {
type Item = (String, Value<T>);
fn next(&mut self) -> Option<Self::Item> {
self.inner.next()
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.inner.size_hint()
}
}
impl<T> ExactSizeIterator for IntoIter<T> {
fn len(&self) -> usize {
self.inner.len()
}
}
impl<'r, T> IntoIterator for &'r Environment<T> {
type Item = (&'r str, &'r Value<T>);
type IntoIter = Iter<'r, T>;
fn into_iter(self) -> Self::IntoIter {
Iter {
inner: self
.variables
.iter()
.map(|(name, value)| (name.as_str(), value)),
}
}
}
type MapFn<'r, T> = fn((&'r String, &'r Value<T>)) -> (&'r str, &'r Value<T>);
/// Iterator over references of the `Environment` entries.
#[derive(Debug)]
pub struct Iter<'r, T> {
inner: iter::Map<hash_map::Iter<'r, String, Value<T>>, MapFn<'r, T>>,
}
impl<'r, T> Iterator for Iter<'r, T> {
type Item = (&'r str, &'r Value<T>);
fn next(&mut self) -> Option<Self::Item> {
self.inner.next()
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.inner.size_hint()
}
}
impl<T> ExactSizeIterator for Iter<'_, T> {
fn len(&self) -> usize {
self.inner.len()
}
}
impl<T, S, V> Extend<(S, V)> for Environment<T>
where
S: Into<String>,
V: Into<Value<T>>,
{
fn extend<I: IntoIterator<Item = (S, V)>>(&mut self, iter: I) {
let variables = iter
.into_iter()
.map(|(var_name, value)| (var_name.into(), value.into()));
self.variables.extend(variables);
}
}