Evaluate basic arithmetic.

7 files changed, 158 insertions, 97 deletions

diff --git a/src/lib/eval/arith.rs b/src/lib/eval/arith.rs
index fae69de..fe3a06b 100644
--- a/src/lib/eval/arith.rs
+++ b/src/lib/eval/arith.rs
@@ -1,34 +1,67 @@
-use std::ops::Add;
+use std::ops::{Add, Sub, Mul, Div};
 use super::super::types::Type;
-use super::super::types::Type::*;
 use super::super::types::Number;
 
+fn apply_arithmetic(
+    func_i: fn(isize, isize) -> isize,
+    func_f: fn(f32, f32) -> f32,
+    operand_a: &Type,
+    operand_b: &Type) -> Result<Type, String> {
+
+    match (operand_a, operand_b) {
+        (Type::Bool(_), _) | (_, Type::Bool(_)) |
+        (Type::Str(_), _) | (_, Type::Str(_)) |
+        (Type::Operator(_), _) | (_, Type::Operator(_)) => {
+            Err("Incompatible types".to_string())
+        },
+
+        (Type::Number(Number::Int(i)), Type::Number(Number::Float(f))) |
+        (Type::Number(Number::Float(f)), Type::Number(Number::Int(i))) => {
+            Ok(Type::Number(Number::Float(func_f(*f, *i as f32))))
+        },
+
+        (Type::Number(Number::Int(a)), Type::Number(Number::Int(b))) => {
+            Ok(Type::Number(Number::Int(func_i(*a, *b))))
+        },
+
+        (Type::Number(Number::Float(a)), Type::Number(Number::Float(b))) => {
+            Ok(Type::Number(Number::Float(func_f(*a, *b))))
+        },
+
+        (Type::Symbol(_), Type::Number(_)) |
+        (Type::Number(_), Type::Symbol(_)) |
+        (Type::Symbol(_), Type::Symbol(_)) => Err("Not yet implemented".to_string())
+    }
+}
+
 impl Add for Type {
     type Output = Result<Type, String>;
 
     fn add(self, other: Type) -> Result<Type, String> {
-        match (self, other) {
-            (Bool(_), _) | (_, Bool(_)) |
-            (Str(_), _) | (_, Str(_)) |
-            (Operator(_), _) | (_, Operator(_)) => {
-                Err("Cannot add these types".to_string())
-            },
-            (Number(Number::Int(i)), Number(Number::Float(f))) |
-            (Number(Number::Float(f)), Number(Number::Int(i))) => {
-                Ok(Number(Number::Float(f + i as f32)))
-            },
-
-            (Number(Number::Int(a)), Number(Number::Int(b))) => {
-                Ok(Number(Number::Int(a + b)))
-            },
-
-            (Number(Number::Float(a)), Number(Number::Float(b))) => {
-                Ok(Number(Number::Float(a + b)))
-            },
-
-            (Symbol(_), Number(_)) |
-            (Number(_), Symbol(_)) |
-            (Symbol(_), Symbol(_)) => Err("Not yet implemented".to_string())
-        }
+        apply_arithmetic(|a, b| a + b, |a, b| a + b, &self, &other)
+    }
+}
+
+impl Sub for Type {
+    type Output = Result<Type, String>;
+
+    fn sub(self, other: Type) -> Result<Type, String> {
+        apply_arithmetic(|a, b| a - b, |a, b| a - b, &self, &other)
+    }
+}
+
+impl Mul for Type {
+    type Output = Result<Type, String>;
+
+    fn mul(self, other: Type) -> Result<Type, String> {
+        apply_arithmetic(|a, b| a * b, |a, b| a * b, &self, &other)
+    }
+}
+
+impl Div for Type {
+    type Output = Result<Type, String>;
+
+    fn div(self, other: Type) -> Result<Type, String> {
+        apply_arithmetic(|a, b| a / b, |a, b| a / b, &self, &other)
     }
 }
diff --git a/src/lib/eval/mod.rs b/src/lib/eval/mod.rs
index b582397..adee0e5 100644
--- a/src/lib/eval/mod.rs
+++ b/src/lib/eval/mod.rs
@@ -1,54 +1,84 @@
-use std::collections::HashMap;
 use super::types::Op;
 use super::types::Op::*;
-use super::types::SEXP;
-use super::types::SEXP::*;
-use super::types::Type::*;
+use super::sexpr::SExpr;
+use super::sexpr::SExpr::*;
+use super::types::Type;
 use super::types::Number;
+use super::environment::Environment;
 
 pub mod arith;
 
-pub type Env = HashMap<String, SEXP>;
-
-pub fn eval(expr: &SEXP, env: &mut Env) -> Result<SEXP, String> {
+pub fn eval(expr: &SExpr, env: &mut Environment) -> Result<SExpr, String> {
     match expr {
         Atom(ref x) => Ok(Atom((*x).clone())),
         Sexpr(ref s) => seval(s, env)
     }
 }
 
-fn seval(sexpr: &[SEXP], env: &mut Env) -> Result<SEXP, String> {
+fn seval(sexpr: &[SExpr], env: &mut Environment) -> Result<SExpr, String> {
     if sexpr.is_empty() {
         return Err("Empty S Expression".to_string())
     }
 
     let op = match &sexpr[0] {
-        Atom(Operator(x)) => *x,
-        Atom(Symbol(_s)) => return Err("Not yet implemented".to_string()),
+        Atom(Type::Operator(x)) => *x,
+        Atom(Type::Symbol(_s)) => return Err("Not yet implemented".to_string()),
         x => return Err(format!("{:?} is not a procedure", x))
     };
 
     op_eval(op, &sexpr[1..], env)
 }
 
-fn op_eval(op: Op, expr: &[SEXP], env: &mut Env) -> Result<SEXP, String> {
+fn op_eval(op: Op, expr: &[SExpr], env: &mut Environment) -> Result<SExpr, String> {
     match op {
         Add => op_add(expr, env),
+        Sub => op_sub(expr, env),
+        Mul => op_mul(expr, env),
+        Div => op_div(expr, env),
         //Define => define(expr, env),
         _ => Err("Not yet implemented".to_string())
     }
 }
 
-fn op_add(expr: &[SEXP], env: &mut Env) -> Result<SEXP, String> {
-    let mut acc = Number(Number::Int(0));
+fn arith_op(
+    expr: &[SExpr],
+    env: &mut Environment,
+    identity: Number,
+    f: fn(Type, Type) -> Result<Type, String>) -> Result<SExpr, String>{
+
+    let mut acc = Type::Number(identity);
     let mut i = 0;
+    if expr.len() > 1 {
+        let b = match eval(&expr[i], env)? {
+            Atom(x) => x,
+            Sexpr(_) => panic!("This should have evaluated to an atom")
+        };
+        acc = b;
+        i = 1;
+    }
     while i < expr.len() {
         let b = match eval(&expr[i], env)? {
             Atom(x) => x,
             Sexpr(_) => panic!("This should have evaluated to an atom")
         };
-        acc = (acc + b)?;
-        i += 1;
+        acc = (f(acc, b))?;
+        i += 1
     }
-    Ok(SEXP::Atom(acc))
+    Ok(SExpr::Atom(acc))
+}
+
+fn op_add(expr: &[SExpr], env: &mut Environment) -> Result<SExpr, String> {
+    arith_op(expr, env, Number::Int(0), |a, b| a + b)
+}
+
+fn op_sub(expr: &[SExpr], env: &mut Environment) -> Result<SExpr, String> {
+    arith_op(expr, env, Number::Int(0), |a, b| a - b)
+}
+
+fn op_mul(expr: &[SExpr], env: &mut Environment) -> Result<SExpr, String> {
+    arith_op(expr, env, Number::Int(1), |a, b| a * b)
+}
+
+fn op_div(expr: &[SExpr], env: &mut Environment) -> Result<SExpr, String> {
+    arith_op(expr, env, Number::Float(1.0), |a, b| a / b)
 }
diff --git a/src/lib/mod.rs b/src/lib/mod.rs
index a547a2d..bf4584c 100644
--- a/src/lib/mod.rs
+++ b/src/lib/mod.rs
@@ -1,3 +1,5 @@
-pub mod types;
-pub mod parse;
+pub mod environment;
 pub mod eval;
+pub mod parse;
+pub mod sexpr;
+pub mod types;
diff --git a/src/lib/parse.rs b/src/lib/parse.rs
index 8e9c785..047b374 100644
--- a/src/lib/parse.rs
+++ b/src/lib/parse.rs
@@ -1,7 +1,7 @@
 use super::types::Type;
 use super::types::Number;
 use super::types::Op;
-use super::types::SEXP;
+use super::sexpr::SExpr;
 
 pub type MaybeToken = (Option<Result<Token, String>>, usize);
 
@@ -250,7 +250,7 @@ pub fn is_float(word: &str) -> MaybeToken {
     }
 }
 
-pub fn parse(expr: &str) -> Result<SEXP, String> {
+pub fn parse(expr: &str) -> Result<SExpr, String> {
     let mut tokenstream = TokenStream::default(expr);
     match tokenstream.peek() {
         Some(Ok(Token::LParen)) => {
@@ -258,13 +258,13 @@ pub fn parse(expr: &str) -> Result<SEXP, String> {
             descend(&mut tokenstream)
         },
         Some(Ok(Token::RParen)) => Err("Malformed expression".to_string()),
-        Some(Ok(Token::Value(x))) => Ok(SEXP::Atom(x)),
+        Some(Ok(Token::Value(x))) => Ok(SExpr::Atom(x)),
         Some(Err(f)) => Err(f),
         None => Err("Empty expression".to_string())
     }
 }
 
-pub fn descend(tokenstream: &mut TokenStream) -> Result<SEXP, String> {
+pub fn descend(tokenstream: &mut TokenStream) -> Result<SExpr, String> {
     let mut sexp = Vec::new();
     loop {
         let token = match tokenstream.next() {
@@ -286,11 +286,11 @@ pub fn descend(tokenstream: &mut TokenStream) -> Result<SEXP, String> {
                 break;
             },
             Token::Value(atom) => {
-                sexp.push(SEXP::Atom(atom));
+                sexp.push(SExpr::Atom(atom));
                 continue;
             }
         }
     }
 
-    Ok(SEXP::Sexpr(sexp))
+    Ok(SExpr::Sexpr(sexp))
 }
diff --git a/src/lib/sexpr.rs b/src/lib/sexpr.rs
index 0d37332..a6fbe49 100644
--- a/src/lib/sexpr.rs
+++ b/src/lib/sexpr.rs
@@ -1,7 +1,45 @@
 use super::types::Type;
 
-pub enum SEXP {
+#[derive(PartialEq, Debug)]
+pub enum SExpr {
     Atom(Type),
-    List(Vec<SEXP>)
+    Sexpr(Vec<SExpr>)
 }
 
+#[test]
+fn construct() {
+    let atom1 = SExpr::Atom(Type::Number(Number::Int(1)));
+    let atom2 = SExpr::Atom(Type::Number(Number::Int(2)));
+    let atom3 = SExpr::Atom(Type::Number(Number::Int(3)));
+    let atom4 = SExpr::Atom(Type::Number(Number::Int(4)));
+    let sexp = SExpr::Sexpr(vec!(atom1, atom2, atom3, atom4));
+    match sexp {
+        SExpr::Sexpr(ref x) => {
+            assert_eq!(x[0], SExpr::Atom(Type::Number(Number::Int(1))));
+        },
+        _ => panic!("What")
+    }
+}
+
+#[test]
+fn mutability() {
+    let atom1 = SExpr::Atom(Type::Number(Number::Int(1)));
+    let atom2 = SExpr::Atom(Type::Number(Number::Int(2)));
+    let atom3 = SExpr::Atom(Type::Number(Number::Int(3)));
+    let atom4 = SExpr::Atom(Type::Number(Number::Int(4)));
+    let mut sexp = SExpr::Sexpr(vec!(atom1, atom2, atom3, atom4));
+    match sexp {
+        SExpr::Sexpr(ref mut x) => match x[0] {
+            SExpr::Atom(Type::Number(Number::Int(ref mut x))) => *x += 7,
+            _ => panic!("What")
+        },
+        _ => panic!("What")
+    }
+
+    match sexp {
+        SExpr::Sexpr(ref x) => {
+            assert_eq!(x[0], SExpr::Atom(Type::Number(Number::Int(8))));
+        },
+        _ => panic!("What")
+    }
+}
diff --git a/src/lib/types.rs b/src/lib/types.rs
index 4c2900a..7755c04 100644
--- a/src/lib/types.rs
+++ b/src/lib/types.rs
@@ -51,47 +51,4 @@ pub enum Type {
     Operator(Op),
 }
 
-#[derive(PartialEq, Debug)]
-pub enum SEXP {
-    Atom(Type),
-    Sexpr(Vec<SEXP>)
-}
-
-#[test]
-fn construct() {
-    let atom1 = SEXP::Atom(Type::Number(Number::Int(1)));
-    let atom2 = SEXP::Atom(Type::Number(Number::Int(2)));
-    let atom3 = SEXP::Atom(Type::Number(Number::Int(3)));
-    let atom4 = SEXP::Atom(Type::Number(Number::Int(4)));
-    let sexp = SEXP::Sexpr(vec!(atom1, atom2, atom3, atom4));
-    match sexp {
-        SEXP::Sexpr(ref x) => {
-            assert_eq!(x[0], SEXP::Atom(Type::Number(Number::Int(1))));
-        },
-        _ => panic!("What")
-    }
-}
-
-#[test]
-fn mutability() {
-    let atom1 = SEXP::Atom(Type::Number(Number::Int(1)));
-    let atom2 = SEXP::Atom(Type::Number(Number::Int(2)));
-    let atom3 = SEXP::Atom(Type::Number(Number::Int(3)));
-    let atom4 = SEXP::Atom(Type::Number(Number::Int(4)));
-    let mut sexp = SEXP::Sexpr(vec!(atom1, atom2, atom3, atom4));
-    match sexp {
-        SEXP::Sexpr(ref mut x) => match x[0] {
-            SEXP::Atom(Type::Number(Number::Int(ref mut x))) => *x += 7,
-            _ => panic!("What")
-        },
-        _ => panic!("What")
-    }
-
-    match sexp {
-        SEXP::Sexpr(ref x) => {
-            assert_eq!(x[0], SEXP::Atom(Type::Number(Number::Int(8))));
-        },
-        _ => panic!("What")
-    }
-}
 
diff --git a/src/main.rs b/src/main.rs
index 15cf60b..49c916a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,6 +6,8 @@ pub mod lib;
 use rustyline::error::ReadlineError;
 use rustyline::Editor;
 
+use lib::environment::Environment;
+
 fn read<T: rustyline::Helper>(rl: &mut Editor<T>) -> Option<String> {
     let readline = rl.readline(">> ");
     match readline {
@@ -35,13 +37,12 @@ fn means_exit(input: &str) -> bool {
     }
 }
 
-fn eval(env: &mut lib::eval::Env, input: &str) -> String {
+fn eval(env: &mut Environment, input: &str) -> String {
     let sexp = match lib::parse::parse(input) {
         Ok(x) => x,
         Err(f) => return f
     };
 
-    println!("{:?}", sexp);
     let res = lib::eval::eval(&sexp, env);
     match res {
         Ok(x) => format!("{:?}", x),
@@ -50,7 +51,7 @@ fn eval(env: &mut lib::eval::Env, input: &str) -> String {
 }
 
 fn main() {
-    let mut env = lib::eval::Env::new();
+    let mut env = Environment::new();
     let hist_file = "history.txt";
 
     // `()` can be used when no completer is required