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use super::Term;
#[derive(Clone, Debug, Default)]
pub struct Context {
vars: Vec<String>,
}
impl Context {
/// # Examples
/// ```
/// use chomp::ast::convert::Context;
///
/// let context = Context::new();
/// assert_eq!(context.get("x"), None);
/// assert_eq!(context.get("y"), None);
/// assert_eq!(context.get("z"), None);
/// ```
pub fn new() -> Self {
Self::default()
}
/// # Examples
/// ```
/// use chomp::ast::convert::Context;
///
/// let context = Context::new();
/// assert_eq!(context.get("x"), None);
///
/// context.push("x".to_owned(), |c| {
/// assert_eq!(c.get("x"), Some(0));
///
/// c.push("y".to_owned(), |c| {
/// assert_eq!(c.get("x"), Some(1));
/// })
/// });
///
/// assert_eq!(context.get("x"), None);
/// ```
pub fn get<T: ?Sized + PartialEq<str>>(&self, name: &T) -> Option<usize> {
let mut iter = self.vars.iter();
let mut pos = 0;
while let Some(var) = iter.next_back() {
if T::eq(&name, &var) {
return Some(pos);
} else {
pos += 1;
}
}
None
}
/// # Examples
/// ```
/// use chomp::ast::convert::Context;
///
/// let context = Context::new();
/// assert_eq!(context.get("x"), None);
///
/// context.push("x".to_owned(), |c| {
/// assert_eq!(c.get("x"), Some(0));
/// });
///
/// assert_eq!(context.get("x"), None);
/// ```
pub fn push<F: FnOnce(&Self) -> T, T>(&self, var: String, f: F) -> T {
let mut context = self.clone();
context.vars.push(var);
f(&context)
}
}
pub trait Convert {
fn convert(self, context: &Context) -> Term;
}
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