2 files changed, 45 insertions, 3 deletions
diff --git a/users/grfn/achilles/src/interpreter/mod.rs b/users/grfn/achilles/src/interpreter/mod.rs
index a8ba2dd3acdc..70df7a0724a5 100644
--- a/users/grfn/achilles/src/interpreter/mod.rs
+++ b/users/grfn/achilles/src/interpreter/mod.rs
@@ -1,9 +1,12 @@
 mod error;
 mod value;
 
+use itertools::Itertools;
+use value::Val;
+
 pub use self::error::{Error, Result};
 pub use self::value::{Function, Value};
-use crate::ast::hir::{Binding, Expr};
+use crate::ast::hir::{Binding, Expr, Pattern};
 use crate::ast::{BinaryOperator, FunctionType, Ident, Literal, Type, UnaryOperator};
 use crate::common::env::Env;
 
@@ -24,6 +27,17 @@ impl<'a> Interpreter<'a> {
             .ok_or_else(|| Error::UndefinedVariable(var.to_owned()))
     }
 
+    fn bind_pattern(&mut self, pattern: &'a Pattern<'a, Type>, value: Value<'a>) {
+        match pattern {
+            Pattern::Id(id, _) => self.env.set(id, value),
+            Pattern::Tuple(pats) => {
+                for (pat, val) in pats.iter().zip(value.as_tuple().unwrap().clone()) {
+                    self.bind_pattern(pat, val);
+                }
+            }
+        }
+    }
+
     pub fn eval(&mut self, expr: &'a Expr<'a, Type>) -> Result<Value<'a>> {
         let res = match expr {
             Expr::Ident(id, _) => self.resolve(id),
@@ -53,9 +67,9 @@ impl<'a> Interpreter<'a> {
             }
             Expr::Let { bindings, body, .. } => {
                 self.env.push();
-                for Binding { ident, body, .. } in bindings {
+                for Binding { pat, body, .. } in bindings {
                     let val = self.eval(body)?;
-                    self.env.set(ident, val);
+                    self.bind_pattern(pat, val);
                 }
                 let res = self.eval(body)?;
                 self.env.pop();
@@ -115,6 +129,13 @@ impl<'a> Interpreter<'a> {
                     body: (**body).to_owned(),
                 }))
             }
+            Expr::Tuple(members, _) => Ok(Val::Tuple(
+                members
+                    .into_iter()
+                    .map(|expr| self.eval(expr))
+                    .try_collect()?,
+            )
+            .into()),
         }?;
         debug_assert_eq!(&res.type_(), expr.type_());
         Ok(res)
diff --git a/users/grfn/achilles/src/interpreter/value.rs b/users/grfn/achilles/src/interpreter/value.rs
index 55ba42f9de58..272d1167a33c 100644
--- a/users/grfn/achilles/src/interpreter/value.rs
+++ b/users/grfn/achilles/src/interpreter/value.rs
@@ -6,6 +6,7 @@ use std::rc::Rc;
 use std::result;
 
 use derive_more::{Deref, From, TryInto};
+use itertools::Itertools;
 
 use super::{Error, Result};
 use crate::ast::hir::Expr;
@@ -25,6 +26,7 @@ pub enum Val<'a> {
     Float(f64),
     Bool(bool),
     String(Cow<'a, str>),
+    Tuple(Vec<Value<'a>>),
     Function(Function<'a>),
 }
 
@@ -49,6 +51,7 @@ impl<'a> fmt::Debug for Val<'a> {
             Val::Function(Function { type_, .. }) => {
                 f.debug_struct("Function").field("type_", type_).finish()
             }
+            Val::Tuple(members) => f.debug_tuple("Tuple").field(members).finish(),
         }
     }
 }
@@ -79,6 +82,7 @@ impl<'a> Display for Val<'a> {
             Val::Bool(x) => x.fmt(f),
             Val::String(s) => write!(f, "{:?}", s),
             Val::Function(Function { type_, .. }) => write!(f, "<{}>", type_),
+            Val::Tuple(members) => write!(f, "({})", members.iter().join(", ")),
         }
     }
 }
@@ -91,6 +95,7 @@ impl<'a> Val<'a> {
             Val::Bool(_) => Type::Bool,
             Val::String(_) => Type::CString,
             Val::Function(Function { type_, .. }) => Type::Function(type_.clone()),
+            Val::Tuple(members) => Type::Tuple(members.iter().map(|expr| expr.type_()).collect()),
         }
     }
 
@@ -114,6 +119,22 @@ impl<'a> Val<'a> {
             }),
         }
     }
+
+    pub fn as_tuple(&self) -> Option<&Vec<Value<'a>>> {
+        if let Self::Tuple(v) = self {
+            Some(v)
+        } else {
+            None
+        }
+    }
+
+    pub fn try_into_tuple(self) -> result::Result<Vec<Value<'a>>, Self> {
+        if let Self::Tuple(v) = self {
+            Ok(v)
+        } else {
+            Err(self)
+        }
+    }
 }
 
 #[derive(Debug, PartialEq, Clone, Deref)]