4 files changed, 246 insertions, 0 deletions
diff --git a/users/aspen/achilles/src/common/env.rs b/users/aspen/achilles/src/common/env.rs
new file mode 100644
index 000000000000..59a5e46c466f
--- /dev/null
+++ b/users/aspen/achilles/src/common/env.rs
@@ -0,0 +1,59 @@
+use std::borrow::Borrow;
+use std::collections::HashMap;
+use std::hash::Hash;
+use std::mem;
+
+/// A lexical environment
+#[derive(Debug, PartialEq, Eq)]
+pub struct Env<K: Eq + Hash, V>(Vec<HashMap<K, V>>);
+
+impl<K, V> Default for Env<K, V>
+where
+    K: Eq + Hash,
+{
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<K, V> Env<K, V>
+where
+    K: Eq + Hash,
+{
+    pub fn new() -> Self {
+        Self(vec![Default::default()])
+    }
+
+    pub fn push(&mut self) {
+        self.0.push(Default::default());
+    }
+
+    pub fn pop(&mut self) {
+        self.0.pop();
+    }
+
+    pub fn save(&mut self) -> Self {
+        mem::take(self)
+    }
+
+    pub fn restore(&mut self, saved: Self) {
+        *self = saved;
+    }
+
+    pub fn set(&mut self, k: K, v: V) {
+        self.0.last_mut().unwrap().insert(k, v);
+    }
+
+    pub fn resolve<'a, Q>(&'a self, k: &Q) -> Option<&'a V>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        for ctx in self.0.iter().rev() {
+            if let Some(res) = ctx.get(k) {
+                return Some(res);
+            }
+        }
+        None
+    }
+}
diff --git a/users/aspen/achilles/src/common/error.rs b/users/aspen/achilles/src/common/error.rs
new file mode 100644
index 000000000000..51575a895e91
--- /dev/null
+++ b/users/aspen/achilles/src/common/error.rs
@@ -0,0 +1,59 @@
+use std::{io, result};
+
+use thiserror::Error;
+
+use crate::{codegen, interpreter, parser, tc};
+
+#[derive(Error, Debug)]
+pub enum Error {
+    #[error(transparent)]
+    IOError(#[from] io::Error),
+
+    #[error("Error parsing input: {0}")]
+    ParseError(#[from] parser::Error),
+
+    #[error("Error evaluating expression: {0}")]
+    EvalError(#[from] interpreter::Error),
+
+    #[error("Compile error: {0}")]
+    CodegenError(#[from] codegen::Error),
+
+    #[error("Type error: {0}")]
+    TypeError(#[from] tc::Error),
+
+    #[error("{0}")]
+    Message(String),
+}
+
+impl From<String> for Error {
+    fn from(s: String) -> Self {
+        Self::Message(s)
+    }
+}
+
+impl<'a> From<&'a str> for Error {
+    fn from(s: &'a str) -> Self {
+        Self::Message(s.to_owned())
+    }
+}
+
+impl<'a> From<nom::Err<nom::error::Error<&'a str>>> for Error {
+    fn from(e: nom::Err<nom::error::Error<&'a str>>) -> Self {
+        use nom::error::Error as NomError;
+        use nom::Err::*;
+
+        Self::ParseError(match e {
+            Incomplete(i) => Incomplete(i),
+            Error(NomError { input, code }) => Error(NomError {
+                input: input.to_owned(),
+                code,
+            }),
+            Failure(NomError { input, code }) => Failure(NomError {
+                input: input.to_owned(),
+                code,
+            }),
+        })
+    }
+}
+
+pub type Result<T> = result::Result<T, Error>;
diff --git a/users/aspen/achilles/src/common/mod.rs b/users/aspen/achilles/src/common/mod.rs
new file mode 100644
index 000000000000..8368a6dd180f
--- /dev/null
+++ b/users/aspen/achilles/src/common/mod.rs
@@ -0,0 +1,6 @@
+pub(crate) mod env;
+pub(crate) mod error;
+pub(crate) mod namer;
+
+pub use error::{Error, Result};
+pub use namer::{Namer, NamerOf};
diff --git a/users/aspen/achilles/src/common/namer.rs b/users/aspen/achilles/src/common/namer.rs
new file mode 100644
index 000000000000..016e9f6ed99a
--- /dev/null
+++ b/users/aspen/achilles/src/common/namer.rs
@@ -0,0 +1,122 @@
+use std::fmt::Display;
+use std::marker::PhantomData;
+
+pub struct Namer<T, F> {
+    make_name: F,
+    counter: u64,
+    _phantom: PhantomData<T>,
+}
+
+impl<T, F> Namer<T, F> {
+    pub fn new(make_name: F) -> Self {
+        Namer {
+            make_name,
+            counter: 0,
+            _phantom: PhantomData,
+        }
+    }
+}
+
+impl Namer<String, Box<dyn Fn(u64) -> String>> {
+    pub fn with_prefix<T>(prefix: T) -> Self
+    where
+        T: Display + 'static,
+    {
+        Namer::new(move |i| format!("{}{}", prefix, i)).boxed()
+    }
+
+    pub fn with_suffix<T>(suffix: T) -> Self
+    where
+        T: Display + 'static,
+    {
+        Namer::new(move |i| format!("{}{}", i, suffix)).boxed()
+    }
+
+    pub fn alphabetic() -> Self {
+        Namer::new(|i| {
+            if i <= 26 {
+                std::char::from_u32((i + 96) as u32).unwrap().to_string()
+            } else {
+                format!(
+                    "{}{}",
+                    std::char::from_u32(((i % 26) + 96) as u32).unwrap(),
+                    i - 26
+                )
+            }
+        })
+        .boxed()
+    }
+}
+
+impl<T, F> Namer<T, F>
+where
+    F: Fn(u64) -> T,
+{
+    pub fn make_name(&mut self) -> T {
+        self.counter += 1;
+        (self.make_name)(self.counter)
+    }
+
+    pub fn boxed(self) -> NamerOf<T>
+    where
+        F: 'static,
+    {
+        Namer {
+            make_name: Box::new(self.make_name),
+            counter: self.counter,
+            _phantom: self._phantom,
+        }
+    }
+
+    pub fn map<G, U>(self, f: G) -> NamerOf<U>
+    where
+        G: Fn(T) -> U + 'static,
+        T: 'static,
+        F: 'static,
+    {
+        Namer {
+            counter: self.counter,
+            make_name: Box::new(move |x| f((self.make_name)(x))),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+pub type NamerOf<T> = Namer<T, Box<dyn Fn(u64) -> T>>;
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn prefix() {
+        let mut namer = Namer::with_prefix("t");
+        assert_eq!(namer.make_name(), "t1");
+        assert_eq!(namer.make_name(), "t2");
+    }
+
+    #[test]
+    fn suffix() {
+        let mut namer = Namer::with_suffix("t");
+        assert_eq!(namer.make_name(), "1t");
+        assert_eq!(namer.make_name(), "2t");
+    }
+
+    #[test]
+    fn alphabetic() {
+        let mut namer = Namer::alphabetic();
+        assert_eq!(namer.make_name(), "a");
+        assert_eq!(namer.make_name(), "b");
+        (0..25).for_each(|_| {
+            namer.make_name();
+        });
+        assert_eq!(namer.make_name(), "b2");
+    }
+
+    #[test]
+    fn custom_callback() {
+        let mut namer = Namer::new(|n| n + 1);
+        assert_eq!(namer.make_name(), 2);
+        assert_eq!(namer.make_name(), 3);
+    }
+}