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pub mod step;
pub mod util;
pub mod subst;
pub mod display;
/// A leaf node for S-Expressions.
///
/// May represent built-in operators,
/// variables, functions (to be added) or values.
#[derive(Debug)]
#[derive(PartialEq)]
#[derive(Clone)]
pub enum SLeaf {
Add,
Sub,
Mul,
Div,
Eq,
Neq,
Gt,
Lt,
Ge,
Le,
And,
Or,
Not,
Xor,
Quote,
Vector,
Let,
Print,
Int(i32),
True,
False,
Var(String),
Nil,
}
/// An S-Expression; the defining structure of the language.
///
/// This structure is not intended to correspond with
/// IETF-standardized s-expressions; they are only inspiration.
#[derive(Debug)]
#[derive(PartialEq)]
#[derive(Clone)]
pub enum SExp {
SCons(Box<SExp>, Box<SExp>),
Atom(SLeaf),
}
use SExp::*;
use SLeaf::*;
impl SExp {
/// Quick test that lets are values
/// ```rust
/// use myslip::sexp::{SExp::*, SLeaf::*, util::*};
/// assert!(scons(Let, scons(var("a"), scons(5, Nil))).is_value())
/// ```
pub fn is_value(&self) -> bool {
match self {
SCons(a, b) =>
SCons(a.clone(), b.clone()).check_let().is_some() ||
(
(**a == Atom(Quote) || **a == Atom(Vector))
&& b.consists_of_values()
),
Atom(Var(_)) => false,
Atom(_) => true,
}
}
pub fn consists_of_values(&self) -> bool {
self.is_value() || match self {
SCons(a, b) if (*a).is_value() => b.consists_of_values(),
_ => false
}
}
}
|
