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use std::iter;
use crate::sexp::SExp;
use crate::sexp::SLeaf;
use crate::sexp::SExp::*;
use crate::sexp::SLeaf::*;
impl From<i32> for Box<SExp> {
fn from(int: i32) -> Self {
Box::new(Atom(Int(int)))
}
}
impl From<bool> for SExp {
fn from(bl: bool) -> Self {
Atom( if bl { True } else { False } )
}
}
impl From<SLeaf> for Box<SExp> {
fn from(leaf: SLeaf) -> Self {
Box::new(Atom(leaf))
}
}
impl From<i32> for SLeaf {
fn from(int: i32) -> Self {
Int(int)
}
}
pub fn scons(x: impl Into<Box<SExp>>, y: impl Into<Box<SExp>>) -> SExp {
SCons(x.into(), y.into())
}
pub fn var(name: &str) -> SExp {
Atom(Var(name.to_string()))
}
impl SExp {
/// Transforms this SExp into a Vec<SLeaf>.
///
/// Errors if the left-hand side of SCons has an SCons,
/// or if the passed SExp is an Atom, or if the
/// lists aren't Nil-terminated.
///
/// ```rust
/// use myslip::sexp::{SExp::*, SLeaf::*, util::*};
/// assert_eq!(
/// scons(1, scons(2, scons(3, Nil))).into_vec(),
/// Ok(vec![Int(1), Int(2), Int(3)])
/// );
/// assert!(scons(scons(1, Nil), Nil).into_vec().is_err());
/// assert!(scons(1, 2).into_vec().is_err());
/// ```
pub fn into_vec(self) -> Result<Vec<SLeaf>, String> {
match self {
SCons(a, b) => match (*a, *b) {
(Atom(a), Atom(Nil)) => Ok(iter::once(a).collect::<Vec<SLeaf>>()),
(Atom(a), b) => Ok(iter::once(a).chain(b.into_vec()?).collect::<Vec<SLeaf>>()),
(a, b) => Err(format!("invalid list structure: {:?}", scons(a, b)))
},
_ => Err("expected list, found atom".to_string()),
}
}
pub fn parts(self) -> Vec<SExp> {
match self {
Atom(x) => vec![Atom(x)],
SCons(a, b) if *b == Atom(Nil) => vec![*a],
SCons(a, b) => {
let mut res = vec![*a];
res.extend_from_slice(&(*b).parts());
res
},
}
}
pub fn check_let(self) -> Option<(String, SExp)> {
match &(self.parts())[..] {
[l, n, v] if *l == Atom(Let) => match (n.clone(), v.clone()) {
(Atom(Var(name)), val) => Some((name, val)),
_ => None
},
_ => None
}
}
pub fn get_vars_bound_by_pattern(&self) -> Vec<String> {
match self {
Atom(Var(s)) => vec![s.clone()],
Atom(RestPat(s)) => vec![s.clone()],
SCons(a, b) =>
(*a).get_vars_bound_by_pattern()
.into_iter()
.chain((*b).get_vars_bound_by_pattern())
.collect(),
_ => vec![],
}
}
pub fn get_case_scrut_pats_and_arms(self) ->
Option<(SExp, Vec<(SExp, SExp)>)> {
let (scrutinee, patarms) = self.check_case()?;
let scrutinee = match scrutinee {
SCons(q, v) if *q == Atom(Quote) || *q == Atom(Vector) => *v,
t => t,
};
let mut res = vec![];
for patarm in patarms {
let (pat, arm) = match patarm {
SCons(pat, arm) => Some((*pat, *arm)),
_ => {
println!("warn: invalid structure in case arms,");
println!(" should be unreachable after type checking");
None
},
}?;
let arm = match arm {
SCons(x, n) if *n == Atom(Nil) => *x,
t => t,
};
res.push((pat, arm));
}
Some((scrutinee, res))
}
pub fn check_case(self) -> Option<(SExp, Vec<SExp>)> {
match &(self.parts())[..] {
[casekw, scrutinee, cases @ ..] if casekw.clone() == Atom(Case) =>
Some((scrutinee.clone(), cases.to_vec())),
_ => None,
}
}
pub fn back_to_case(scrutinee: SExp, arms: Vec<SExp>) -> SExp {
let mut res = Atom(Nil);
for arm in arms.into_iter().rev() {
res = scons(arm, res);
}
scons(Case, scons(scrutinee, res))
}
}
|
