diff --git a/.idea/cozo.iml b/.idea/cozo.iml
index 14c4f514..c1724834 100644
--- a/.idea/cozo.iml
+++ b/.idea/cozo.iml
@@ -4,8 +4,10 @@
     <content url="file://$MODULE_DIR$">
       <sourceFolder url="file://$MODULE_DIR$/cozo_parser/src" isTestSource="false" />
       <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/src/ast/op/src" isTestSource="false" />
       <excludeFolder url="file://$MODULE_DIR$/target" />
       <excludeFolder url="file://$MODULE_DIR$/cozo_parser/target" />
+      <excludeFolder url="file://$MODULE_DIR$/src/ast/op/target" />
     </content>
     <orderEntry type="inheritedJdk" />
     <orderEntry type="sourceFolder" forTests="false" />
diff --git a/src/ast/eval_op.rs b/src/ast/eval_op.rs
new file mode 100644
index 00000000..4e47538c
--- /dev/null
+++ b/src/ast/eval_op.rs
@@ -0,0 +1,451 @@
+use crate::ast::Expr;
+use crate::ast::Expr::*;
+use crate::ast::op::Op;
+use crate::error::CozoError;
+use crate::error::CozoError::*;
+use crate::value::Value::*;
+
+pub fn add_exprs<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    match exprs {
+        [a, b] => {
+            let a = a.eval()?;
+            let b = b.eval()?;
+            if a == Const(Null) || b == Const(Null) {
+                return Ok(Const(Null));
+            }
+            Ok(Const(match (a, b) {
+                (Const(a), Const(b)) => {
+                    match (a, b) {
+                        (Int(va), Int(vb)) => Int(va + vb),
+                        (Float(va), Int(vb)) => Float(va + vb as f64),
+                        (Int(va), Float(vb)) => Float(va as f64 + vb),
+                        (Float(va), Float(vb)) => Float(va + vb),
+                        (OwnString(va), OwnString(vb)) => OwnString(Box::new(*va + &*vb)),
+                        (OwnString(va), RefString(vb)) => OwnString(Box::new(*va + &*vb)),
+                        (RefString(va), OwnString(vb)) => OwnString(Box::new(va.to_string() + &*vb)),
+                        (RefString(va), RefString(vb)) => OwnString(Box::new(va.to_string() + &*vb)),
+                        (_, _) => return Err(CozoError::TypeError)
+                    }
+                }
+                (a, b) => return Ok(Apply(Op::Add, vec![a, b]))
+            }))
+        }
+        _ => unreachable!()
+    }
+}
+
+pub fn sub_exprs<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    match exprs {
+        [a, b] => {
+            let a = a.eval()?;
+            let b = b.eval()?;
+            if a == Const(Null) || b == Const(Null) {
+                return Ok(Const(Null));
+            }
+            Ok(Const(match (a, b) {
+                (Const(a), Const(b)) => {
+                    match (a, b) {
+                        (Int(va), Int(vb)) => Int(va - vb),
+                        (Float(va), Int(vb)) => Float(va - vb as f64),
+                        (Int(va), Float(vb)) => Float(va as f64 - vb),
+                        (Float(va), Float(vb)) => Float(va - vb),
+                        (_, _) => return Err(CozoError::TypeError)
+                    }
+                }
+                (a, b) => return Ok(Apply(Op::Sub, vec![a, b]))
+            }))
+        }
+        _ => unreachable!()
+    }
+}
+
+pub fn mul_exprs<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    match exprs {
+        [a, b] => {
+            let a = a.eval()?;
+            let b = b.eval()?;
+            if a == Const(Null) || b == Const(Null) {
+                return Ok(Const(Null));
+            }
+            Ok(Const(match (a, b) {
+                (Const(a), Const(b)) => {
+                    match (a, b) {
+                        (Int(va), Int(vb)) => Int(va * vb),
+                        (Float(va), Int(vb)) => Float(va * vb as f64),
+                        (Int(va), Float(vb)) => Float(va as f64 * vb),
+                        (Float(va), Float(vb)) => Float(va * vb),
+                        (_, _) => return Err(CozoError::TypeError)
+                    }
+                }
+                (a, b) => return Ok(Apply(Op::Mul, vec![a, b]))
+            }))
+        }
+        _ => unreachable!()
+    }
+}
+
+
+pub fn div_exprs<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    match exprs {
+        [a, b] => {
+            let a = a.eval()?;
+            let b = b.eval()?;
+            if a == Const(Null) || b == Const(Null) {
+                return Ok(Const(Null));
+            }
+            Ok(Const(match (a, b) {
+                (Const(a), Const(b)) => {
+                    match (a, b) {
+                        (Int(va), Int(vb)) => Float(va as f64 / vb as f64),
+                        (Float(va), Int(vb)) => Float(va / vb as f64),
+                        (Int(va), Float(vb)) => Float(va as f64 / vb),
+                        (Float(va), Float(vb)) => Float(va / vb),
+                        (_, _) => return Err(CozoError::TypeError)
+                    }
+                }
+                (a, b) => return Ok(Apply(Op::Div, vec![a, b]))
+            }))
+        }
+        _ => unreachable!()
+    }
+}
+
+pub fn mod_exprs<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    match exprs {
+        [a, b] => {
+            let a = a.eval()?;
+            let b = b.eval()?;
+            if a == Const(Null) || b == Const(Null) {
+                return Ok(Const(Null));
+            }
+            Ok(Const(match (a, b) {
+                (Const(a), Const(b)) => {
+                    match (a, b) {
+                        (Int(a), Int(b)) => Int(a % b),
+                        (_, _) => return Err(CozoError::TypeError)
+                    }
+                }
+                (a, b) => return Ok(Apply(Op::Mod, vec![a, b]))
+            }))
+        }
+        _ => unreachable!()
+    }
+}
+
+
+pub fn eq_exprs<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    match exprs {
+        [a, b] => {
+            let a = a.eval()?;
+            let b = b.eval()?;
+            if a == Const(Null) || b == Const(Null) {
+                return Ok(Const(Null));
+            }
+            match (a, b) {
+                (Const(a), Const(b)) => Ok(Const(Bool(a == b))),
+                (a, b) => Ok(Apply(Op::Eq, vec![a, b]))
+            }
+        }
+        _ => unreachable!()
+    }
+}
+
+
+pub fn ne_exprs<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    match exprs {
+        [a, b] => {
+            let a = a.eval()?;
+            let b = b.eval()?;
+            if a == Const(Null) || b == Const(Null) {
+                return Ok(Const(Null));
+            }
+            match (a, b) {
+                (Const(a), Const(b)) => Ok(Const(Bool(a == b))),
+                (a, b) => Ok(Apply(Op::Neq, vec![a, b]))
+            }
+        }
+        _ => unreachable!()
+    }
+}
+
+
+pub fn gt_exprs<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    match exprs {
+        [a, b] => {
+            let a = a.eval()?;
+            let b = b.eval()?;
+            if a == Const(Null) || b == Const(Null) {
+                return Ok(Const(Null));
+            }
+            match (a, b) {
+                (Const(a), Const(b)) => {
+                    match (a, b) {
+                        (Int(a), Int(b)) => Ok(Const(Bool(a > b))),
+                        (Float(a), Int(b)) => Ok(Const(Bool(a > b as f64))),
+                        (Int(a), Float(b)) => Ok(Const(Bool(a as f64 > b))),
+                        (Float(a), Float(b)) => Ok(Const(Bool(a > b))),
+                        (_, _) => Err(CozoError::TypeError)
+                    }
+                }
+                (a, b) => Ok(Apply(Op::Gt, vec![a, b]))
+            }
+        }
+        _ => unreachable!()
+    }
+}
+
+
+pub fn ge_exprs<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    match exprs {
+        [a, b] => {
+            let a = a.eval()?;
+            let b = b.eval()?;
+            if a == Const(Null) || b == Const(Null) {
+                return Ok(Const(Null));
+            }
+            match (a, b) {
+                (Const(a), Const(b)) => {
+                    match (a, b) {
+                        (Int(a), Int(b)) => Ok(Const(Bool(a >= b))),
+                        (Float(a), Int(b)) => Ok(Const(Bool(a >= b as f64))),
+                        (Int(a), Float(b)) => Ok(Const(Bool(a as f64 >= b))),
+                        (Float(a), Float(b)) => Ok(Const(Bool(a >= b))),
+                        (_, _) => Err(CozoError::TypeError)
+                    }
+                }
+                (a, b) => Ok(Apply(Op::Ge, vec![a, b]))
+            }
+        }
+        _ => unreachable!()
+    }
+}
+
+
+pub fn lt_exprs<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    match exprs {
+        [a, b] => {
+            let a = a.eval()?;
+            let b = b.eval()?;
+            if a == Const(Null) || b == Const(Null) {
+                return Ok(Const(Null));
+            }
+            match (a, b) {
+                (Const(a), Const(b)) => {
+                    match (a, b) {
+                        (Int(a), Int(b)) => Ok(Const(Bool(a < b))),
+                        (Float(a), Int(b)) => Ok(Const(Bool(a < b as f64))),
+                        (Int(a), Float(b)) => Ok(Const(Bool((a as f64) < b))),
+                        (Float(a), Float(b)) => Ok(Const(Bool(a < b))),
+                        (_, _) => Err(CozoError::TypeError)
+                    }
+                }
+                (a, b) => Ok(Apply(Op::Lt, vec![a, b]))
+            }
+        }
+        _ => unreachable!()
+    }
+}
+
+pub fn le_exprs<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    match exprs {
+        [a, b] => {
+            let a = a.eval()?;
+            let b = b.eval()?;
+            if a == Const(Null) || b == Const(Null) {
+                return Ok(Const(Null));
+            }
+            match (a, b) {
+                (Const(a), Const(b)) => {
+                    match (a, b) {
+                        (Int(a), Int(b)) => Ok(Const(Bool(a <= b))),
+                        (Float(a), Int(b)) => Ok(Const(Bool(a <= b as f64))),
+                        (Int(a), Float(b)) => Ok(Const(Bool((a as f64) <= b))),
+                        (Float(a), Float(b)) => Ok(Const(Bool(a <= b))),
+                        (_, _) => Err(CozoError::TypeError)
+                    }
+                }
+                (a, b) => Ok(Apply(Op::Le, vec![a, b]))
+            }
+        }
+        _ => unreachable!()
+    }
+}
+
+
+pub fn pow_exprs<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    match exprs {
+        [a, b] => {
+            let a = a.eval()?;
+            let b = b.eval()?;
+            if a == Const(Null) || b == Const(Null) {
+                return Ok(Const(Null));
+            }
+            match (a, b) {
+                (Const(a), Const(b)) => {
+                    match (a, b) {
+                        (Int(a), Int(b)) => Ok(Const(Float((a as f64).powf(b as f64)))),
+                        (Float(a), Int(b)) => Ok(Const(Float(a.powi(b as i32)))),
+                        (Int(a), Float(b)) => Ok(Const(Float((a as f64).powf(b)))),
+                        (Float(a), Float(b)) => Ok(Const(Float(a.powf(b)))),
+                        (_, _) => Err(CozoError::TypeError)
+                    }
+                }
+                (a, b) => Ok(Apply(Op::Pow, vec![a, b]))
+            }
+        }
+        _ => unreachable!()
+    }
+}
+
+pub fn coalesce_exprs<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    match exprs {
+        [a, b] => {
+            let a = a.eval()?;
+            let b = b.eval()?;
+            if a == Const(Null) {
+                return Ok(b);
+            }
+            if b == Const(Null) {
+                return Ok(a);
+            }
+            if let a @ Const(_) = a {
+                return Ok(a);
+            }
+            return Ok(Apply(Op::Coalesce, vec![a, b]));
+        }
+        _ => unreachable!()
+    }
+}
+
+pub fn negate_expr<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    Ok(match exprs {
+        [a] => {
+            match a.eval()? {
+                Const(Null) => Const(Null),
+                Const(Bool(b)) => Const(Bool(!b)),
+                Const(_) => return Err(TypeError),
+                Apply(Op::Neg, v) => v.into_iter().next().unwrap(),
+                Apply(Op::IsNull, v) => Apply(Op::NotNull, v),
+                Apply(Op::NotNull, v) => Apply(Op::IsNull, v),
+                Apply(Op::Eq, v) => Apply(Op::Neq, v),
+                Apply(Op::Neq, v) => Apply(Op::Eq, v),
+                Apply(Op::Gt, v) => Apply(Op::Le, v),
+                Apply(Op::Ge, v) => Apply(Op::Lt, v),
+                Apply(Op::Le, v) => Apply(Op::Gt, v),
+                Apply(Op::Lt, v) => Apply(Op::Ge, v),
+                v => Apply(Op::Neg, vec![v])
+            }
+        }
+        _ => unreachable!()
+    })
+}
+
+
+pub fn minus_expr<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    Ok(match exprs {
+        [a] => {
+            match a.eval()? {
+                Const(Null) => Const(Null),
+                Const(Int(i)) => Const(Int(-i)),
+                Const(Float(f)) => Const(Float(-f)),
+                Const(_) => return Err(TypeError),
+                Apply(Op::Minus, v) => v.into_iter().next().unwrap(),
+                v => Apply(Op::Minus, vec![v])
+            }
+        }
+        _ => unreachable!()
+    })
+}
+
+
+pub fn is_null_expr<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    Ok(match exprs {
+        [a] => {
+            match a.eval()? {
+                Const(Null) => Const(Bool(true)),
+                Const(_) => Const(Bool(false)),
+                v => Apply(Op::IsNull, vec![v])
+            }
+        }
+        _ => unreachable!()
+    })
+}
+
+pub fn not_null_expr<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    Ok(match exprs {
+        [a] => {
+            match a.eval()? {
+                Const(Null) => Const(Bool(false)),
+                Const(_) => Const(Bool(true)),
+                v => Apply(Op::IsNull, vec![v])
+            }
+        }
+        _ => unreachable!()
+    })
+}
+
+pub fn or_expr<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    let mut unevaluated = vec![];
+    let mut has_null = false;
+    for expr in exprs {
+        match expr.eval()? {
+            Const(Bool(true)) => return Ok(Const(Bool(true))),
+            Const(Bool(false)) => {}
+            Const(Null) => { has_null = true},
+            Const(_) => return Err(TypeError),
+            Apply(Op::Or, vs) => {
+                for el in vs {
+                    match el {
+                        Const(Null) => has_null = true,
+                        Const(_) => unreachable!(),
+                        v => unevaluated.push(v)
+                    }
+                }
+            }
+            v => unevaluated.push(v)
+        }
+    }
+    match (has_null, unevaluated.len()) {
+        (true, 0) => Ok(Const(Null)),
+        (false, 0) => Ok(Const(Bool(false))),
+        (false, _) => Ok(Apply(Op::Or, unevaluated)),
+        (true, _) => {
+            unevaluated.push(Const(Null));
+            Ok(Apply(Op::Or, unevaluated))
+        }
+    }
+}
+
+
+
+pub fn and_expr<'a>(exprs: &[Expr<'a>]) -> Result<Expr<'a>, CozoError> {
+    let mut unevaluated = vec![];
+    let mut no_null = true;
+    for expr in exprs {
+        match expr.eval()? {
+            Const(Bool(false)) => return Ok(Const(Bool(false))),
+            Const(Bool(true)) => {},
+            Const(Null) => no_null = false,
+            Const(_) => return Err(TypeError),
+            Apply(Op::Or, vs) => {
+                for el in vs {
+                    match el {
+                        Const(Null) => no_null = false,
+                        Const(_) => unreachable!(),
+                        v => unevaluated.push(v)
+                    }
+                }
+            }
+            v => unevaluated.push(v)
+        }
+    }
+    match (no_null, unevaluated.len()) {
+        (true, 0) => Ok(Const(Bool(true))),
+        (false, 0) => Ok(Const(Null)),
+        (true, _) => Ok(Apply(Op::Add, unevaluated)),
+        (false, _) => {
+            unevaluated.push(Const(Null));
+            Ok(Apply(Op::And, unevaluated))
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/ast.rs b/src/ast/mod.rs
similarity index 61%
rename from src/ast.rs
rename to src/ast/mod.rs
index 07f89a0a..fcc831e0 100644
--- a/src/ast.rs
+++ b/src/ast/mod.rs
@@ -4,31 +4,14 @@ use pest::prec_climber::{Assoc, PrecClimber, Operator};
 use crate::parser::Parser;
 use crate::parser::Rule;
 use lazy_static::lazy_static;
-use crate::ast::Expr::Const;
+use crate::ast::eval_op::*;
+use crate::ast::Expr::{Apply, Const};
+use crate::ast::op::Op;
+use crate::error::CozoError;
 use crate::value::Value;
-use thiserror::Error;
 
-#[derive(Error, Debug)]
-pub enum CozoError {
-    #[error("Invalid UTF code")]
-    InvalidUtfCode,
-
-    #[error("Type mismatch")]
-    InfixTypeMismatch {
-        op: Rule,
-        lhs: Value<'static>,
-        rhs: Value<'static>,
-    },
-
-    #[error(transparent)]
-    ParseInt(#[from] std::num::ParseIntError),
-
-    #[error(transparent)]
-    ParseFloat(#[from] std::num::ParseFloatError),
-
-    #[error(transparent)]
-    Parse(#[from] pest::error::Error<Rule>),
-}
+mod eval_op;
+mod op;
 
 
 lazy_static! {
@@ -49,72 +32,69 @@ lazy_static! {
     };
 }
 
+
 #[derive(PartialEq, Debug)]
 pub enum Expr<'a> {
-    UnaryOp,
-    BinaryOp,
-    AssocOp,
-    Accessor,
-    FnCall,
+    Apply(Op, Vec<Expr<'a>>),
     Const(Value<'a>),
 }
 
+impl<'a> Expr<'a> {
+    pub fn eval(&self) -> Result<Expr<'a>, CozoError> {
+        match self {
+            Apply(op, args) => {
+                match op {
+                    Op::Add => add_exprs(args),
+                    Op::Sub => sub_exprs(args),
+                    Op::Mul => mul_exprs(args),
+                    Op::Div => div_exprs(args),
+                    Op::Eq => eq_exprs(args),
+                    Op::Neq => ne_exprs(args),
+                    Op::Gt => gt_exprs(args),
+                    Op::Lt => lt_exprs(args),
+                    Op::Ge => ge_exprs(args),
+                    Op::Le => le_exprs(args),
+                    Op::Neg => negate_expr(args),
+                    Op::Minus => minus_expr(args),
+                    Op::Mod => mod_exprs(args),
+                    Op::Or => or_expr(args),
+                    Op::And => and_expr(args),
+                    Op::Coalesce => coalesce_exprs(args),
+                    Op::Pow => pow_exprs(args),
+                    Op::IsNull => is_null_expr(args),
+                    Op::NotNull => not_null_expr(args),
+                    Op::Call => unimplemented!(),
+                }
+            }
+            Const(v) => Ok(Const(v.clone()))
+        }
+    }
+}
+
 fn build_expr_infix<'a>(lhs: Result<Expr<'a>, CozoError>, op: Pair<Rule>, rhs: Result<Expr<'a>, CozoError>) -> Result<Expr<'a>, CozoError> {
     let lhs = lhs?;
     let rhs = rhs?;
-    if let (Const(a), Const(b)) = (lhs, rhs) {
-        let rule = op.as_rule();
-        return match rule {
-            Rule::op_add => {
-                match (a, b) {
-                    (Value::Null, _) => Ok(Const(Value::Null)),
-                    (_, Value::Null) => Ok(Const(Value::Null)),
-                    (Value::Int(va), Value::Int(vb)) => Ok(Const(Value::Int(va + vb))),
-                    (Value::Float(va), Value::Int(vb)) => Ok(Const(Value::Float(va + vb as f64))),
-                    (Value::Int(va), Value::Float(vb)) => Ok(Const(Value::Float(va as f64 + vb))),
-                    (Value::Float(va), Value::Float(vb)) => Ok(Const(Value::Float(va + vb))),
-                    (Value::OwnString(va), Value::OwnString(vb)) => Ok(Const(Value::OwnString(Box::new(*va + &*vb)))),
-                    (Value::OwnString(va), Value::RefString(vb)) => Ok(Const(Value::OwnString(Box::new(*va + &*vb)))),
-                    (Value::RefString(va), Value::OwnString(vb)) => Ok(Const(Value::OwnString(Box::new(va.to_string() + &*vb)))),
-                    (Value::RefString(va), Value::RefString(vb)) => Ok(Const(Value::OwnString(Box::new(va.to_string() + &*vb)))),
-                    (a, b) => Err(CozoError::InfixTypeMismatch { op: rule, lhs: a.into_owned(), rhs: b.into_owned() })
-                }
-            }
-            Rule::op_sub => {
-                match (a, b) {
-                    (Value::Null, _) => Ok(Const(Value::Null)),
-                    (_, Value::Null) => Ok(Const(Value::Null)),
-                    (Value::Int(va), Value::Int(vb)) => Ok(Const(Value::Int(va - vb))),
-                    (Value::Float(va), Value::Int(vb)) => Ok(Const(Value::Float(va - vb as f64))),
-                    (Value::Int(va), Value::Float(vb)) => Ok(Const(Value::Float(va as f64 - vb))),
-                    (Value::Float(va), Value::Float(vb)) => Ok(Const(Value::Float(va - vb))),
-                    (a, b) => Err(CozoError::InfixTypeMismatch { op: rule, lhs: a.into_owned(), rhs: b.into_owned() })
-                }
-            }
-            Rule::op_mul => {
-                match (a, b) {
-                    (Value::Null, _) => Ok(Const(Value::Null)),
-                    (_, Value::Null) => Ok(Const(Value::Null)),
-                    (Value::Int(va), Value::Int(vb)) => Ok(Const(Value::Int(va * vb))),
-                    (Value::Float(va), Value::Int(vb)) => Ok(Const(Value::Float(va * vb as f64))),
-                    (Value::Int(va), Value::Float(vb)) => Ok(Const(Value::Float(va as f64 * vb))),
-                    (Value::Float(va), Value::Float(vb)) => Ok(Const(Value::Float(va * vb))),
-                    (a, b) => Err(CozoError::InfixTypeMismatch { op: rule, lhs: a.into_owned(), rhs: b.into_owned() })
-                }
-            }
-            Rule::op_div => {
-                match (a, b) {
-                    (Value::Null, _) => Ok(Const(Value::Null)),
-                    (_, Value::Null) => Ok(Const(Value::Null)),
-                    (Value::Int(va), Value::Int(vb)) => Ok(Const(Value::Float(va as f64 / vb as f64))),
-                    (Value::Float(va), Value::Int(vb)) => Ok(Const(Value::Float(va / vb as f64))),
-                    (Value::Int(va), Value::Float(vb)) => Ok(Const(Value::Float(va as f64 / vb))),
-                    (Value::Float(va), Value::Float(vb)) => Ok(Const(Value::Float(va / vb))),
-                    (a, b) => Err(CozoError::InfixTypeMismatch { op: rule, lhs: a.into_owned(), rhs: b.into_owned() })
-                }
-            }
-            Rule::op_eq => Ok(Const(Value::Bool(a == b))),
-            Rule::op_ne => Ok(Const(Value::Bool(a != b))),
+    let op = match op.as_rule() {
+        Rule::op_add => Op::Add,
+        Rule::op_sub => Op::Sub,
+        Rule::op_mul => Op::Mul,
+        Rule::op_div => Op::Div,
+        Rule::op_eq => Op::Eq,
+        Rule::op_ne => Op::Neq,
+        Rule::op_or => Op::Or,
+        Rule::op_and => Op::And,
+        Rule::op_mod => Op::Mod,
+        Rule::op_gt => Op::Gt,
+        Rule::op_ge => Op::Ge,
+        Rule::op_lt => Op::Lt,
+        Rule::op_le => Op::Le,
+        Rule::op_pow => Op::Pow,
+        Rule::op_coalesce => Op::Coalesce,
+        _ => unreachable!()
+    };
+    Ok(Apply(op, vec![lhs, rhs]))
+    /*
+        /*
             Rule::op_or => {
                 match (a, b) {
                     (Value::Null, Value::Null) => Ok(Const(Value::Null)),
@@ -133,12 +113,8 @@ fn build_expr_infix<'a>(lhs: Result<Expr<'a>, CozoError>, op: Pair<Rule>, rhs: R
                     (a, b) => Err(CozoError::InfixTypeMismatch { op: rule, lhs: a.into_owned(), rhs: b.into_owned() })
                 }
             }
-            Rule::op_coalesce => Ok(if a == Value::Null { Const(b) } else { Const(a) }),
-            _ => { unimplemented!() }
-        };
-    } else {
-        unimplemented!()
-    }
+         */
+        */
 }
 
 #[inline]
@@ -148,7 +124,7 @@ fn parse_int(s: &str, radix: u32) -> i64 {
 
 #[inline]
 fn parse_quoted_string(pairs: Pairs<Rule>) -> Result<String, CozoError> {
-    let mut ret = String::new();
+    let mut ret = String::with_capacity(pairs.as_str().len());
     for pair in pairs {
         let s = pair.as_str();
         match s {
@@ -165,6 +141,7 @@ fn parse_quoted_string(pairs: Pairs<Rule>) -> Result<String, CozoError> {
                 let ch = char::from_u32(code).ok_or(CozoError::InvalidUtfCode)?;
                 ret.push(ch);
             }
+            s if s.starts_with('\\') => return Err(CozoError::InvalidEscapeSequence),
             s => ret.push_str(s)
         }
     }
@@ -174,7 +151,7 @@ fn parse_quoted_string(pairs: Pairs<Rule>) -> Result<String, CozoError> {
 
 #[inline]
 fn parse_s_quoted_string(pairs: Pairs<Rule>) -> Result<String, CozoError> {
-    let mut ret = String::new();
+    let mut ret = String::with_capacity(pairs.as_str().len());
     for pair in pairs {
         let s = pair.as_str();
         match s {
@@ -191,6 +168,7 @@ fn parse_s_quoted_string(pairs: Pairs<Rule>) -> Result<String, CozoError> {
                 let ch = char::from_u32(code).ok_or(CozoError::InvalidUtfCode)?;
                 ret.push(ch);
             }
+            s if s.starts_with('\\') => return Err(CozoError::InvalidEscapeSequence),
             s => ret.push_str(s)
         }
     }
@@ -201,6 +179,26 @@ fn build_expr_primary(pair: Pair<Rule>) -> Result<Expr, CozoError> {
     match pair.as_rule() {
         Rule::expr => build_expr_primary(pair.into_inner().next().unwrap()),
         Rule::term => build_expr_primary(pair.into_inner().next().unwrap()),
+        Rule::grouping => build_expr(pair.into_inner().next().unwrap()),
+
+        Rule::unary => {
+            let mut inner = pair.into_inner();
+            let op = inner.next().unwrap().as_rule();
+            let term = build_expr_primary(inner.next().unwrap())?;
+            /*
+            match (op, term) {
+                (Rule::minus, Const(Value::Int(i))) => Ok(Const(Value::Int(-i))),
+                (Rule::minus, Const(Value::Float(f))) => Ok(Const(Value::Float(-f))),
+                (_, Const(term)) => Err(PrefixTypeMismatch { op, term: term.into_owned() }),
+                (_, _) => unimplemented!()
+            }
+             */
+            Ok(Apply(match op {
+                Rule::negate => Op::Neg,
+                Rule::minus => Op::Minus,
+                _ => unreachable!()
+            }, vec![term]))
+        }
 
         Rule::pos_int => Ok(Const(Value::Int(pair.as_str().replace('_', "").parse::<i64>()?))),
         Rule::hex_pos_int => Ok(Const(Value::Int(parse_int(pair.as_str(), 16)))),
@@ -255,6 +253,11 @@ mod tests {
 
     #[test]
     fn operators() {
-        println!("{:#?}", parse_expr_from_str("1/10+2+3*4").unwrap());
+        println!("{:#?}", parse_expr_from_str("1/10+(-2+3)*4^5").unwrap().eval().unwrap());
+        println!("{:#?}", parse_expr_from_str("true && false").unwrap().eval().unwrap());
+        println!("{:#?}", parse_expr_from_str("true || false").unwrap().eval().unwrap());
+        println!("{:#?}", parse_expr_from_str("true || null").unwrap().eval().unwrap());
+        println!("{:#?}", parse_expr_from_str("null || true").unwrap().eval().unwrap());
+        println!("{:#?}", parse_expr_from_str("true && null").unwrap().eval().unwrap());
     }
 }
\ No newline at end of file
diff --git a/src/ast/op.rs b/src/ast/op.rs
new file mode 100644
index 00000000..1de2cbc3
--- /dev/null
+++ b/src/ast/op.rs
@@ -0,0 +1,24 @@
+
+#[derive(PartialEq, Debug)]
+pub enum Op {
+    Add,
+    Sub,
+    Mul,
+    Div,
+    Eq,
+    Neq,
+    Gt,
+    Lt,
+    Ge,
+    Le,
+    Neg,
+    Minus,
+    Mod,
+    Or,
+    And,
+    Coalesce,
+    Pow,
+    Call,
+    IsNull,
+    NotNull
+}
diff --git a/src/error.rs b/src/error.rs
new file mode 100644
index 00000000..a44f5dd9
--- /dev/null
+++ b/src/error.rs
@@ -0,0 +1,23 @@
+use thiserror::Error;
+use crate::parser::Rule;
+
+#[derive(Error, Debug)]
+pub enum CozoError {
+    #[error("Invalid UTF code")]
+    InvalidUtfCode,
+
+    #[error("Invalid escape sequence")]
+    InvalidEscapeSequence,
+
+    #[error("Type mismatch")]
+    TypeError,
+
+    #[error(transparent)]
+    ParseInt(#[from] std::num::ParseIntError),
+
+    #[error(transparent)]
+    ParseFloat(#[from] std::num::ParseFloatError),
+
+    #[error(transparent)]
+    Parse(#[from] pest::error::Error<Rule>),
+}
diff --git a/src/eval.rs b/src/eval.rs
new file mode 100644
index 00000000..e69de29b
diff --git a/src/function.rs b/src/function.rs
new file mode 100644
index 00000000..fcd2b0f8
--- /dev/null
+++ b/src/function.rs
@@ -0,0 +1,73 @@
+use std::collections::BTreeMap;
+use std::fmt::{Debug, Formatter};
+use crate::typing::{PrimitiveType, Typing};
+use crate::value::Value;
+use lazy_static::lazy_static;
+
+#[derive(PartialEq, Debug)]
+pub struct Function {
+    pub args: Vec<Arg>,
+    pub var_arg: Option<Typing>,
+    pub ret_type: Typing,
+    pub fn_impl: FunctionImpl,
+}
+
+pub enum FunctionImpl {
+    Native(&'static str, for<'a> fn(&[Value<'a>]) -> Value<'a>),
+    UserDefined(()),
+}
+
+impl Debug for FunctionImpl {
+    fn fmt(&self, _f: &mut Formatter<'_>) -> std::fmt::Result {
+        todo!()
+    }
+}
+
+impl PartialEq for FunctionImpl {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (FunctionImpl::Native(a,_), FunctionImpl::Native(b,_)) => a == b,
+            (FunctionImpl::UserDefined(a), FunctionImpl::UserDefined(b)) => a == b,
+            (_, _) => false
+        }
+    }
+}
+
+#[derive(PartialEq, Debug)]
+pub struct Arg {
+    pub typing: Typing,
+    pub default_val: Option<Value<'static>>,
+    pub name: Option<String>,
+}
+
+lazy_static! {
+    static ref BUILT_IN_FUNCTIONS : BTreeMap<&'static str, Function> = {
+        let mut ret = BTreeMap::new();
+
+        fn add_int<'a>(_args: &[Value<'a>]) -> Value<'a> {
+            todo!()
+        }
+
+        fn add_float<'a>(_args: &[Value<'a>]) -> Value<'a> {
+            todo!()
+        }
+
+        ret.insert("_add_int",
+            Function {
+                args: vec![],
+                var_arg: Some(Typing::Primitive(PrimitiveType::Int)),
+                ret_type: Typing::Primitive(PrimitiveType::Int),
+                fn_impl: FunctionImpl::Native("_add_int", add_int)
+            });
+
+        ret.insert("_add_float",
+            Function {
+                args: vec![],
+                var_arg: Some(Typing::Primitive(PrimitiveType::Float)),
+                ret_type: Typing::Primitive(PrimitiveType::Float),
+                fn_impl: FunctionImpl::Native("_add_float", add_float)
+            });
+
+        ret
+    };
+}
diff --git a/src/lib.rs b/src/lib.rs
index 65a9eb03..890b5b1e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,4 +3,6 @@ pub mod typing;
 pub mod env;
 pub mod ast;
 pub mod parser;
-
+pub mod eval;
+pub mod function;
+pub mod error;
\ No newline at end of file