merge(glittershark/achilles): Subtree import at 'b93268085a'

Imported from https://github.com/glittershark/achilles/

git-subtree-dir: users/glittershark/achilles
git-subtree-mainline: 4d193f2395
git-subtree-split: b93268085a
Change-Id: I64a583b454bbe03e20358ad7808939a4cbc212ba

users/glittershark/achilles/src/interpreter/value.rs

@@ -0,0 +1,203 @@
+use std::borrow::Cow;
+use std::convert::TryFrom;
+use std::fmt::{self, Display};
+use std::ops::{Add, Div, Mul, Neg, Sub};
+use std::rc::Rc;
+use std::result;
+
+use derive_more::{Deref, From, TryInto};
+
+use super::{Error, Result};
+use crate::ast::hir::Expr;
+use crate::ast::{FunctionType, Ident, Type};
+
+#[derive(Debug, Clone)]
+pub struct Function<'a> {
+    pub type_: FunctionType<'a>,
+    pub args: Vec<Ident<'a>>,
+    pub body: Expr<'a, Type<'a>>,
+}
+
+#[derive(From, TryInto)]
+#[try_into(owned, ref)]
+pub enum Val<'a> {
+    Int(i64),
+    Float(f64),
+    Bool(bool),
+    String(Cow<'a, str>),
+    Function(Function<'a>),
+}
+
+impl<'a> TryFrom<Val<'a>> for String {
+    type Error = ();
+
+    fn try_from(value: Val<'a>) -> result::Result<Self, Self::Error> {
+        match value {
+            Val::String(s) => Ok(s.into_owned()),
+            _ => Err(()),
+        }
+    }
+}
+
+impl<'a> fmt::Debug for Val<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Val::Int(x) => f.debug_tuple("Int").field(x).finish(),
+            Val::Float(x) => f.debug_tuple("Float").field(x).finish(),
+            Val::Bool(x) => f.debug_tuple("Bool").field(x).finish(),
+            Val::String(s) => f.debug_tuple("String").field(s).finish(),
+            Val::Function(Function { type_, .. }) => {
+                f.debug_struct("Function").field("type_", type_).finish()
+            }
+        }
+    }
+}
+
+impl<'a> PartialEq for Val<'a> {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (Val::Int(x), Val::Int(y)) => x == y,
+            (Val::Float(x), Val::Float(y)) => x == y,
+            (Val::Bool(x), Val::Bool(y)) => x == y,
+            (Val::Function(_), Val::Function(_)) => false,
+            (_, _) => false,
+        }
+    }
+}
+
+impl<'a> From<u64> for Val<'a> {
+    fn from(i: u64) -> Self {
+        Self::from(i as i64)
+    }
+}
+
+impl<'a> Display for Val<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Val::Int(x) => x.fmt(f),
+            Val::Float(x) => x.fmt(f),
+            Val::Bool(x) => x.fmt(f),
+            Val::String(s) => write!(f, "{:?}", s),
+            Val::Function(Function { type_, .. }) => write!(f, "<{}>", type_),
+        }
+    }
+}
+
+impl<'a> Val<'a> {
+    pub fn type_(&self) -> Type {
+        match self {
+            Val::Int(_) => Type::Int,
+            Val::Float(_) => Type::Float,
+            Val::Bool(_) => Type::Bool,
+            Val::String(_) => Type::CString,
+            Val::Function(Function { type_, .. }) => Type::Function(type_.clone()),
+        }
+    }
+
+    pub fn as_type<'b, T>(&'b self) -> Result<&'b T>
+    where
+        T: TypeOf + 'b + Clone,
+        &'b T: TryFrom<&'b Self>,
+    {
+        <&T>::try_from(self).map_err(|_| Error::InvalidType {
+            actual: self.type_().to_owned(),
+            expected: <T as TypeOf>::type_of(),
+        })
+    }
+
+    pub fn as_function<'b>(&'b self, function_type: FunctionType) -> Result<&'b Function<'a>> {
+        match self {
+            Val::Function(f) if f.type_ == function_type => Ok(&f),
+            _ => Err(Error::InvalidType {
+                actual: self.type_().to_owned(),
+                expected: Type::Function(function_type.to_owned()),
+            }),
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, Clone, Deref)]
+pub struct Value<'a>(Rc<Val<'a>>);
+
+impl<'a> Display for Value<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl<'a, T> From<T> for Value<'a>
+where
+    Val<'a>: From<T>,
+{
+    fn from(x: T) -> Self {
+        Self(Rc::new(x.into()))
+    }
+}
+
+impl<'a> Neg for Value<'a> {
+    type Output = Result<Value<'a>>;
+
+    fn neg(self) -> Self::Output {
+        Ok((-self.as_type::<i64>()?).into())
+    }
+}
+
+impl<'a> Add for Value<'a> {
+    type Output = Result<Value<'a>>;
+
+    fn add(self, rhs: Self) -> Self::Output {
+        Ok((self.as_type::<i64>()? + rhs.as_type::<i64>()?).into())
+    }
+}
+
+impl<'a> Sub for Value<'a> {
+    type Output = Result<Value<'a>>;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        Ok((self.as_type::<i64>()? - rhs.as_type::<i64>()?).into())
+    }
+}
+
+impl<'a> Mul for Value<'a> {
+    type Output = Result<Value<'a>>;
+
+    fn mul(self, rhs: Self) -> Self::Output {
+        Ok((self.as_type::<i64>()? * rhs.as_type::<i64>()?).into())
+    }
+}
+
+impl<'a> Div for Value<'a> {
+    type Output = Result<Value<'a>>;
+
+    fn div(self, rhs: Self) -> Self::Output {
+        Ok((self.as_type::<f64>()? / rhs.as_type::<f64>()?).into())
+    }
+}
+
+pub trait TypeOf {
+    fn type_of() -> Type<'static>;
+}
+
+impl TypeOf for i64 {
+    fn type_of() -> Type<'static> {
+        Type::Int
+    }
+}
+
+impl TypeOf for bool {
+    fn type_of() -> Type<'static> {
+        Type::Bool
+    }
+}
+
+impl TypeOf for f64 {
+    fn type_of() -> Type<'static> {
+        Type::Float
+    }
+}
+
+impl TypeOf for String {
+    fn type_of() -> Type<'static> {
+        Type::CString
+    }
+}