diff --git a/src/build/AST.go b/src/build/AST.go
new file mode 100644
index 0000000..b12cc5e
--- /dev/null
+++ b/src/build/AST.go
@@ -0,0 +1,87 @@
+package build
+
+import (
+	"git.akyoto.dev/cli/q/src/build/ast"
+	"git.akyoto.dev/cli/q/src/build/expression"
+	"git.akyoto.dev/cli/q/src/build/keyword"
+	"git.akyoto.dev/cli/q/src/build/token"
+	"git.akyoto.dev/cli/q/src/errors"
+)
+
+// toAST generates an AST from a list of tokens.
+func (f *Function) toAST(tokens token.List) (ast.AST, error) {
+	tree := make(ast.AST, 0, len(tokens)/64)
+
+	err := EachInstruction(tokens, func(instruction token.List) error {
+		node, err := f.toASTNode(instruction)
+
+		if err == nil && node != nil {
+			tree = append(tree, node)
+		}
+
+		return err
+	})
+
+	return tree, err
+}
+
+// toASTNode generates an AST node from an instruction.
+func (f *Function) toASTNode(tokens token.List) (ast.Node, error) {
+	if tokens[0].Kind == token.Keyword {
+		switch tokens[0].Text() {
+		case keyword.Return:
+			value := expression.Parse(tokens[1:])
+			return &ast.Return{Value: value}, nil
+
+		case keyword.Loop:
+			blockStart := tokens.IndexKind(token.BlockStart) + 1
+			blockEnd := tokens.LastIndexKind(token.BlockEnd)
+
+			if blockStart == -1 {
+				return nil, errors.New(errors.MissingBlockStart, f.File, tokens[0].End())
+			}
+
+			if blockEnd == -1 {
+				return nil, errors.New(errors.MissingBlockEnd, f.File, tokens[len(tokens)-1].End())
+			}
+
+			tree, err := f.toAST(tokens[blockStart:blockEnd])
+			return &ast.Loop{Body: tree}, err
+
+		default:
+			return nil, errors.New(&errors.KeywordNotImplemented{Keyword: tokens[0].Text()}, f.File, tokens[0].Position)
+		}
+	}
+
+	expr := expression.Parse(tokens)
+
+	if expr == nil {
+		return nil, nil
+	}
+
+	switch {
+	case isVariableDefinition(expr):
+		if len(expr.Children) < 2 {
+			return nil, errors.New(errors.MissingAssignValue, f.File, expr.LastChild().Token.End())
+		}
+
+		name := expr.Children[0].Token
+		value := expr.Children[1]
+		return &ast.Define{Name: name, Value: value}, nil
+
+	case isAssignment(expr):
+		if len(expr.Children) < 2 {
+			return nil, errors.New(errors.MissingAssignValue, f.File, expr.LastChild().Token.End())
+		}
+
+		name := expr.Children[0].Token
+		value := expr.Children[1]
+		return &ast.Assign{Name: name, Value: value}, nil
+
+	case isFunctionCall(expr):
+		return &ast.Call{Expression: expr}, nil
+
+	default:
+		return nil, errors.New(&errors.InvalidInstruction{Instruction: expr.Token.Text()}, f.File, expr.Token.Position)
+	}
+}
diff --git a/src/build/Call.go b/src/build/Call.go
index ee813fc..44df7c9 100644
--- a/src/build/Call.go
+++ b/src/build/Call.go
@@ -2,6 +2,7 @@ package build
 
 import (
 	"git.akyoto.dev/cli/q/src/build/config"
+	"git.akyoto.dev/cli/q/src/build/cpu"
 	"git.akyoto.dev/cli/q/src/build/expression"
 )
 
@@ -45,3 +46,23 @@ func (f *Function) CompileSyscall(expr *expression.Expression) error {
 	f.sideEffects++
 	return err
 }
+
+// ExpressionsToRegisters moves multiple expressions into the specified registers.
+func (f *Function) ExpressionsToRegisters(expressions []*expression.Expression, registers []cpu.Register) error {
+	for _, register := range registers {
+		f.SaveRegister(register)
+	}
+
+	for i := len(expressions) - 1; i >= 0; i-- {
+		expression := expressions[i]
+		register := registers[i]
+
+		err := f.ExpressionToRegister(expression, register)
+
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
diff --git a/src/build/Execute.go b/src/build/Execute.go
index 4903ef7..6a96ce8 100644
--- a/src/build/Execute.go
+++ b/src/build/Execute.go
@@ -3,7 +3,6 @@ package build
 import (
 	"strconv"
 
-	"git.akyoto.dev/cli/q/src/build/asm"
 	"git.akyoto.dev/cli/q/src/build/config"
 	"git.akyoto.dev/cli/q/src/build/cpu"
 	"git.akyoto.dev/cli/q/src/build/expression"
@@ -72,110 +71,3 @@ func (f *Function) ExecuteLeaf(operation token.Token, register cpu.Register, ope
 
 	return errors.New(errors.NotImplemented, f.File, operation.Position)
 }
-
-// ExpressionToRegister moves the result of an expression into the given register.
-func (f *Function) ExpressionToRegister(root *expression.Expression, register cpu.Register) error {
-	if config.Verbose {
-		f.Logf("%s to register %s", root, register)
-	}
-
-	operation := root.Token
-
-	if root.IsLeaf() {
-		return f.TokenToRegister(operation, register)
-	}
-
-	if isFunctionCall(root) {
-		err := f.CompileFunctionCall(root)
-
-		if err != nil {
-			return err
-		}
-
-		if register != f.cpu.Return[0] {
-			f.assembler.RegisterRegister(asm.MOVE, register, f.cpu.Return[0])
-		}
-
-		return nil
-	}
-
-	left := root.Children[0]
-	right := root.Children[1]
-
-	err := f.ExpressionToRegister(left, register)
-
-	if err != nil {
-		return err
-	}
-
-	f.SaveRegister(register)
-	return f.Execute(operation, register, right)
-}
-
-// ExpressionsToRegisters moves multiple expressions into the specified registers.
-func (f *Function) ExpressionsToRegisters(expressions []*expression.Expression, registers []cpu.Register) error {
-	for _, register := range registers {
-		f.SaveRegister(register)
-	}
-
-	for i := len(expressions) - 1; i >= 0; i-- {
-		expression := expressions[i]
-		register := registers[i]
-
-		err := f.ExpressionToRegister(expression, register)
-
-		if err != nil {
-			return err
-		}
-	}
-
-	return nil
-}
-
-// TokenToRegister moves a token into a register.
-// It only works with identifiers, numbers and strings.
-func (f *Function) TokenToRegister(t token.Token, register cpu.Register) error {
-	switch t.Kind {
-	case token.Identifier:
-		name := t.Text()
-		constant, exists := f.definitions[name]
-
-		if exists {
-			if config.Verbose {
-				f.Logf("constant %s = %s", constant.Name, constant.Value)
-			}
-
-			return f.ExpressionToRegister(constant.Value, register)
-		}
-
-		variable, exists := f.variables[name]
-
-		if !exists {
-			return errors.New(&errors.UnknownIdentifier{Name: name}, f.File, t.Position)
-		}
-
-		if register != variable.Register {
-			f.assembler.RegisterRegister(asm.MOVE, register, variable.Register)
-		}
-
-		f.useVariable(variable)
-		return nil
-
-	case token.Number:
-		value := t.Text()
-		n, err := strconv.Atoi(value)
-
-		if err != nil {
-			return err
-		}
-
-		f.assembler.RegisterNumber(asm.MOVE, register, n)
-		return nil
-
-	case token.String:
-		return errors.New(errors.NotImplemented, f.File, t.Position)
-
-	default:
-		return errors.New(errors.InvalidExpression, f.File, t.Position)
-	}
-}
diff --git a/src/build/ExpressionToRegister.go b/src/build/ExpressionToRegister.go
new file mode 100644
index 0000000..9a6f09d
--- /dev/null
+++ b/src/build/ExpressionToRegister.go
@@ -0,0 +1,47 @@
+package build
+
+import (
+	"git.akyoto.dev/cli/q/src/build/asm"
+	"git.akyoto.dev/cli/q/src/build/config"
+	"git.akyoto.dev/cli/q/src/build/cpu"
+	"git.akyoto.dev/cli/q/src/build/expression"
+)
+
+// ExpressionToRegister moves the result of an expression into the given register.
+func (f *Function) ExpressionToRegister(root *expression.Expression, register cpu.Register) error {
+	if config.Verbose {
+		f.Logf("%s to register %s", root, register)
+	}
+
+	operation := root.Token
+
+	if root.IsLeaf() {
+		return f.TokenToRegister(operation, register)
+	}
+
+	if isFunctionCall(root) {
+		err := f.CompileFunctionCall(root)
+
+		if err != nil {
+			return err
+		}
+
+		if register != f.cpu.Return[0] {
+			f.assembler.RegisterRegister(asm.MOVE, register, f.cpu.Return[0])
+		}
+
+		return nil
+	}
+
+	left := root.Children[0]
+	right := root.Children[1]
+
+	err := f.ExpressionToRegister(left, register)
+
+	if err != nil {
+		return err
+	}
+
+	f.SaveRegister(register)
+	return f.Execute(operation, register, right)
+}
diff --git a/src/build/Function.go b/src/build/Function.go
index d615a90..39bf0c3 100644
--- a/src/build/Function.go
+++ b/src/build/Function.go
@@ -3,6 +3,7 @@ package build
 import (
 	"fmt"
 
+	"git.akyoto.dev/cli/q/src/build/ast"
 	"git.akyoto.dev/cli/q/src/build/config"
 	"git.akyoto.dev/cli/q/src/build/expression"
 	"git.akyoto.dev/cli/q/src/build/fs"
@@ -11,8 +12,8 @@ import (
 
 // Function represents a function.
 type Function struct {
-	Name string
 	File *fs.File
+	Name string
 	Body token.List
 	compiler
 }
@@ -26,61 +27,60 @@ func (f *Function) Compile() {
 }
 
 // CompileTokens compiles a token list.
-func (f *Function) CompileTokens(body token.List) error {
-	start := 0
-	groupLevel := 0
-	blockLevel := 0
+func (f *Function) CompileTokens(tokens token.List) error {
+	tree, err := f.toAST(tokens)
 
-	for i, t := range body {
-		if start == i && t.Kind == token.NewLine {
-			start = i + 1
-			continue
+	if err != nil {
+		return err
+	}
+
+	return f.CompileAST(tree)
+}
+
+// CompileAST compiles an abstract syntax tree.
+func (f *Function) CompileAST(tree ast.AST) error {
+	for _, node := range tree {
+		if config.Verbose {
+			f.Logf("%T %s", node, node)
 		}
 
-		switch t.Kind {
-		case token.NewLine:
-			if groupLevel > 0 || blockLevel > 0 {
-				continue
-			}
+		if config.Assembler {
+			f.debug = append(f.debug, debug{
+				position: len(f.assembler.Instructions),
+				source:   node,
+			})
+		}
 
-			instruction := body[start:i]
+		err := f.CompileNode(node)
 
-			if config.Verbose {
-				f.Logf("compiling: %s", instruction)
-			}
-
-			if config.Assembler {
-				f.debug = append(f.debug, debug{
-					position: len(f.assembler.Instructions),
-					source:   instruction,
-				})
-			}
-
-			err := f.CompileInstruction(instruction)
-
-			if err != nil {
-				return err
-			}
-
-			start = i + 1
-
-		case token.GroupStart:
-			groupLevel++
-
-		case token.GroupEnd:
-			groupLevel--
-
-		case token.BlockStart:
-			blockLevel++
-
-		case token.BlockEnd:
-			blockLevel--
+		if err != nil {
+			return err
 		}
 	}
 
 	return nil
 }
 
+// CompileNode compiles a node in the AST.
+func (f *Function) CompileNode(node ast.Node) error {
+	switch node := node.(type) {
+	case *ast.Call:
+		return f.CompileFunctionCall(node.Expression)
+
+	case *ast.Define:
+		return f.CompileVariableDefinition(node)
+
+	case *ast.Return:
+		return f.CompileReturn(node)
+
+	case *ast.Loop:
+		return f.CompileLoop(node)
+
+	default:
+		panic("Unknown AST type")
+	}
+}
+
 // Logf formats a message for verbose output.
 func (f *Function) Logf(format string, data ...any) {
 	fmt.Printf("[%s @ %d] %s\n", f, len(f.assembler.Instructions), fmt.Sprintf(format, data...))
diff --git a/src/build/Instruction.go b/src/build/Instruction.go
index c668258..944ab92 100644
--- a/src/build/Instruction.go
+++ b/src/build/Instruction.go
@@ -1,36 +1,48 @@
 package build
 
 import (
-	"git.akyoto.dev/cli/q/src/build/expression"
 	"git.akyoto.dev/cli/q/src/build/token"
-	"git.akyoto.dev/cli/q/src/errors"
 )
 
-// CompileInstruction compiles a single instruction.
-func (f *Function) CompileInstruction(instruction token.List) error {
-	if instruction[0].Kind == token.Keyword {
-		return f.CompileKeyword(instruction)
+// EachInstruction calls the function on each instruction.
+func EachInstruction(body token.List, call func(token.List) error) error {
+	start := 0
+	groupLevel := 0
+	blockLevel := 0
+
+	for i, t := range body {
+		if start == i && t.Kind == token.NewLine {
+			start = i + 1
+			continue
+		}
+
+		switch t.Kind {
+		case token.NewLine:
+			if groupLevel > 0 || blockLevel > 0 {
+				continue
+			}
+
+			err := call(body[start:i])
+
+			if err != nil {
+				return err
+			}
+
+			start = i + 1
+
+		case token.GroupStart:
+			groupLevel++
+
+		case token.GroupEnd:
+			groupLevel--
+
+		case token.BlockStart:
+			blockLevel++
+
+		case token.BlockEnd:
+			blockLevel--
+		}
 	}
 
-	expr := expression.Parse(instruction)
-
-	if expr == nil {
-		return nil
-	}
-
-	defer expr.Close()
-
-	switch true {
-	case isVariableDefinition(expr):
-		return f.CompileVariableDefinition(expr)
-
-	case isAssignment(expr):
-		return f.CompileAssignment(expr)
-
-	case isFunctionCall(expr):
-		return f.CompileFunctionCall(expr)
-
-	default:
-		return errors.New(&errors.InvalidInstruction{Instruction: expr.Token.Text()}, f.File, expr.Token.Position)
-	}
+	return nil
 }
diff --git a/src/build/Keyword.go b/src/build/Keyword.go
deleted file mode 100644
index 80e5ee9..0000000
--- a/src/build/Keyword.go
+++ /dev/null
@@ -1,20 +0,0 @@
-package build
-
-import (
-	"git.akyoto.dev/cli/q/src/build/token"
-	"git.akyoto.dev/cli/q/src/errors"
-)
-
-// CompileKeyword compiles an instruction that starts with a keyword.
-func (f *Function) CompileKeyword(tokens token.List) error {
-	switch tokens[0].Text() {
-	case "return":
-		return f.CompileReturn(tokens)
-
-	case "loop":
-		return f.CompileLoop(tokens)
-
-	default:
-		return errors.New(&errors.KeywordNotImplemented{Keyword: tokens[0].Text()}, f.File, tokens[0].Position)
-	}
-}
diff --git a/src/build/Loop.go b/src/build/Loop.go
index 41a9b4f..2165eca 100644
--- a/src/build/Loop.go
+++ b/src/build/Loop.go
@@ -3,26 +3,14 @@ package build
 import (
 	"fmt"
 
-	"git.akyoto.dev/cli/q/src/build/token"
-	"git.akyoto.dev/cli/q/src/errors"
+	"git.akyoto.dev/cli/q/src/build/ast"
 )
 
 // CompileLoop compiles a loop instruction.
-func (f *Function) CompileLoop(tokens token.List) error {
-	blockStart := tokens.IndexKind(token.BlockStart) + 1
-	blockEnd := tokens.LastIndexKind(token.BlockEnd)
-
-	if blockStart == -1 {
-		return errors.New(errors.MissingBlockStart, f.File, tokens[0].End())
-	}
-
-	if blockEnd == -1 {
-		return errors.New(errors.MissingBlockEnd, f.File, tokens[len(tokens)-1].End())
-	}
-
-	loop := fmt.Sprintf("%s_loop_%d", f.Name, f.count.loop)
-	f.assembler.Label(loop)
-	defer f.assembler.Jump(loop)
+func (f *Function) CompileLoop(loop *ast.Loop) error {
+	label := fmt.Sprintf("%s_loop_%d", f.Name, f.count.loop)
+	f.assembler.Label(label)
+	defer f.assembler.Jump(label)
 	f.count.loop++
-	return f.CompileTokens(tokens[blockStart:blockEnd])
+	return f.CompileAST(loop.Body)
 }
diff --git a/src/build/Return.go b/src/build/Return.go
index 8ffd8fb..c661fc7 100644
--- a/src/build/Return.go
+++ b/src/build/Return.go
@@ -1,24 +1,16 @@
 package build
 
 import (
-	"git.akyoto.dev/cli/q/src/build/expression"
-	"git.akyoto.dev/cli/q/src/build/token"
+	"git.akyoto.dev/cli/q/src/build/ast"
 )
 
 // CompileReturn compiles a return instruction.
-func (f *Function) CompileReturn(tokens token.List) error {
+func (f *Function) CompileReturn(node *ast.Return) error {
 	defer f.assembler.Return()
 
-	if len(tokens) == 1 {
+	if node.Value == nil {
 		return nil
 	}
 
-	value := expression.Parse(tokens[1:])
-
-	if value == nil {
-		return nil
-	}
-
-	defer value.Close()
-	return f.ExpressionToRegister(value, f.cpu.Return[0])
+	return f.ExpressionToRegister(node.Value, f.cpu.Return[0])
 }
diff --git a/src/build/TokenToRegister.go b/src/build/TokenToRegister.go
new file mode 100644
index 0000000..6bef4cb
--- /dev/null
+++ b/src/build/TokenToRegister.go
@@ -0,0 +1,59 @@
+package build
+
+import (
+	"strconv"
+
+	"git.akyoto.dev/cli/q/src/build/asm"
+	"git.akyoto.dev/cli/q/src/build/config"
+	"git.akyoto.dev/cli/q/src/build/cpu"
+	"git.akyoto.dev/cli/q/src/build/token"
+	"git.akyoto.dev/cli/q/src/errors"
+)
+
+// TokenToRegister moves a token into a register.
+// It only works with identifiers, numbers and strings.
+func (f *Function) TokenToRegister(t token.Token, register cpu.Register) error {
+	switch t.Kind {
+	case token.Identifier:
+		name := t.Text()
+		constant, exists := f.definitions[name]
+
+		if exists {
+			if config.Verbose {
+				f.Logf("constant %s = %s", constant.Name, constant.Value)
+			}
+
+			return f.ExpressionToRegister(constant.Value, register)
+		}
+
+		variable, exists := f.variables[name]
+
+		if !exists {
+			return errors.New(&errors.UnknownIdentifier{Name: name}, f.File, t.Position)
+		}
+
+		if register != variable.Register {
+			f.assembler.RegisterRegister(asm.MOVE, register, variable.Register)
+		}
+
+		f.useVariable(variable)
+		return nil
+
+	case token.Number:
+		value := t.Text()
+		n, err := strconv.Atoi(value)
+
+		if err != nil {
+			return err
+		}
+
+		f.assembler.RegisterNumber(asm.MOVE, register, n)
+		return nil
+
+	case token.String:
+		return errors.New(errors.NotImplemented, f.File, t.Position)
+
+	default:
+		return errors.New(errors.InvalidExpression, f.File, t.Position)
+	}
+}
diff --git a/src/build/Variable.go b/src/build/Variable.go
index 291d2d4..c81b850 100644
--- a/src/build/Variable.go
+++ b/src/build/Variable.go
@@ -14,6 +14,6 @@ type Variable struct {
 
 // Definitions are single use expressions that don't reside in a register yet.
 type Definition struct {
-	Name  string
 	Value *expression.Expression
+	Name  string
 }
diff --git a/src/build/VariableDefinition.go b/src/build/VariableDefinition.go
index 58a4844..917f12f 100644
--- a/src/build/VariableDefinition.go
+++ b/src/build/VariableDefinition.go
@@ -1,6 +1,7 @@
 package build
 
 import (
+	"git.akyoto.dev/cli/q/src/build/ast"
 	"git.akyoto.dev/cli/q/src/build/config"
 	"git.akyoto.dev/cli/q/src/build/expression"
 	"git.akyoto.dev/cli/q/src/build/token"
@@ -8,24 +9,20 @@ import (
 )
 
 // CompileVariableDefinition compiles a variable definition.
-func (f *Function) CompileVariableDefinition(expr *expression.Expression) error {
-	if len(expr.Children) < 2 {
-		return errors.New(errors.MissingAssignValue, f.File, expr.LastChild().Token.End())
-	}
-
-	name := expr.Children[0].Token.Text()
+func (f *Function) CompileVariableDefinition(node *ast.Define) error {
+	name := node.Name.Text()
 
 	if f.identifierExists(name) {
-		return errors.New(&errors.VariableAlreadyExists{Name: name}, f.File, expr.Children[0].Token.Position)
+		return errors.New(&errors.VariableAlreadyExists{Name: name}, f.File, node.Name.Position)
 	}
 
 	uses := countIdentifier(f.Body, name) - 1
 
 	if uses == 0 {
-		return errors.New(&errors.UnusedVariable{Name: name}, f.File, expr.Children[0].Token.Position)
+		return errors.New(&errors.UnusedVariable{Name: name}, f.File, node.Name.Position)
 	}
 
-	value := expr.Children[1]
+	value := node.Value
 
 	err := value.EachLeaf(func(leaf *expression.Expression) error {
 		if leaf.Token.Kind == token.Identifier && !f.identifierExists(leaf.Token.Text()) {
@@ -40,8 +37,6 @@ func (f *Function) CompileVariableDefinition(expr *expression.Expression) error
 	}
 
 	if uses == 1 {
-		expr.RemoveChild(value)
-
 		f.definitions[name] = &Definition{
 			Name:  name,
 			Value: value,
diff --git a/src/build/asm/Instruction.go b/src/build/asm/Instruction.go
index 5b2bbce..2447bae 100644
--- a/src/build/asm/Instruction.go
+++ b/src/build/asm/Instruction.go
@@ -4,6 +4,6 @@ import "fmt"
 
 // Instruction represents a single instruction which can be converted to machine code.
 type Instruction struct {
-	Mnemonic Mnemonic
 	Data     fmt.Stringer
+	Mnemonic Mnemonic
 }
diff --git a/src/build/asm/Pointer.go b/src/build/asm/Pointer.go
index 9be746f..4e33a63 100644
--- a/src/build/asm/Pointer.go
+++ b/src/build/asm/Pointer.go
@@ -7,7 +7,7 @@ type Address = uint32
 // Position: The machine code offset where the address was inserted.
 // Resolve:  The function that will return the final address.
 type Pointer struct {
+	Resolve  func() Address
 	Position Address
 	Size     uint8
-	Resolve  func() Address
 }
diff --git a/src/build/ast/AST.go b/src/build/ast/AST.go
new file mode 100644
index 0000000..2d8314a
--- /dev/null
+++ b/src/build/ast/AST.go
@@ -0,0 +1,36 @@
+package ast
+
+import (
+	"git.akyoto.dev/cli/q/src/build/expression"
+	"git.akyoto.dev/cli/q/src/build/token"
+)
+
+type Node interface{}
+type AST []Node
+
+type Assign struct {
+	Value *expression.Expression
+	Name  token.Token
+}
+
+type Call struct {
+	Expression *expression.Expression
+}
+
+type Define struct {
+	Value *expression.Expression
+	Name  token.Token
+}
+
+type If struct {
+	Condition *expression.Expression
+	Body      AST
+}
+
+type Loop struct {
+	Body AST
+}
+
+type Return struct {
+	Value *expression.Expression
+}
diff --git a/src/build/compiler.go b/src/build/compiler.go
index 60cfec0..ac28b37 100644
--- a/src/build/compiler.go
+++ b/src/build/compiler.go
@@ -4,23 +4,23 @@ import (
 	"fmt"
 
 	"git.akyoto.dev/cli/q/src/build/asm"
+	"git.akyoto.dev/cli/q/src/build/ast"
 	"git.akyoto.dev/cli/q/src/build/cpu"
-	"git.akyoto.dev/cli/q/src/build/token"
 	"git.akyoto.dev/go/color/ansi"
 )
 
 // compiler is the data structure we embed in each function to preserve compilation state.
 type compiler struct {
-	assembler   asm.Assembler
-	count       counter
-	cpu         cpu.CPU
-	debug       []debug
 	err         error
 	definitions map[string]*Definition
 	variables   map[string]*Variable
 	functions   map[string]*Function
-	sideEffects int
 	finished    chan struct{}
+	assembler   asm.Assembler
+	debug       []debug
+	cpu         cpu.CPU
+	count       counter
+	sideEffects int
 }
 
 // counter stores how often a certain statement appeared so we can generate a unique label from it.
@@ -30,8 +30,8 @@ type counter struct {
 
 // debug is used to look up the source code at the given position.
 type debug struct {
+	source   ast.Node
 	position int
-	source   token.List
 }
 
 // PrintInstructions shows the assembly instructions.
@@ -66,7 +66,7 @@ func (c *compiler) PrintInstructions() {
 }
 
 // sourceAt retrieves the source code at the given position or `nil`.
-func (c *compiler) sourceAt(position int) token.List {
+func (c *compiler) sourceAt(position int) ast.Node {
 	for _, record := range c.debug {
 		if record.position == position {
 			return record.source
diff --git a/src/build/expression/Expression.go b/src/build/expression/Expression.go
index 7776c35..1d2efa8 100644
--- a/src/build/expression/Expression.go
+++ b/src/build/expression/Expression.go
@@ -8,22 +8,22 @@ import (
 
 // Expression is a binary tree with an operator on each node.
 type Expression struct {
-	Token      token.Token
 	Parent     *Expression
 	Children   []*Expression
-	Precedence int
+	Token      token.Token
+	Precedence int8
 }
 
 // New creates a new expression.
 func New() *Expression {
-	return pool.Get().(*Expression)
+	return &Expression{}
 }
 
 // NewLeaf creates a new leaf node.
 func NewLeaf(t token.Token) *Expression {
-	expr := New()
-	expr.Token = t
-	return expr
+	return &Expression{
+		Token: t,
+	}
 }
 
 // AddChild adds a child to the expression.
@@ -32,17 +32,16 @@ func (expr *Expression) AddChild(child *Expression) {
 	child.Parent = expr
 }
 
-// Close puts the expression back into the memory pool.
-func (expr *Expression) Close() {
+// Reset resets all values to the default.
+func (expr *Expression) Reset() {
 	for _, child := range expr.Children {
-		child.Close()
+		child.Reset()
 	}
 
 	expr.Token.Reset()
 	expr.Parent = nil
 	expr.Children = expr.Children[:0]
 	expr.Precedence = 0
-	pool.Put(expr)
 }
 
 // EachLeaf iterates through all leaves in the tree.
diff --git a/src/build/expression/Expression_test.go b/src/build/expression/Expression_test.go
index eb992c6..08c4e5d 100644
--- a/src/build/expression/Expression_test.go
+++ b/src/build/expression/Expression_test.go
@@ -88,7 +88,7 @@ func TestExpressionParse(t *testing.T) {
 			src := []byte(test.Expression)
 			tokens := token.Tokenize(src)
 			expr := expression.Parse(tokens)
-			defer expr.Close()
+			defer expr.Reset()
 
 			assert.NotNil(t, expr)
 			assert.Equal(t, expr.String(), test.Result)
diff --git a/src/build/expression/Operator.go b/src/build/expression/Operator.go
index 5e50dc5..07fc5a1 100644
--- a/src/build/expression/Operator.go
+++ b/src/build/expression/Operator.go
@@ -9,7 +9,7 @@ import (
 // Operator represents an operator for mathematical expressions.
 type Operator struct {
 	Symbol     string
-	Precedence int
+	Precedence int8
 	Operands   int
 }
 
@@ -39,14 +39,14 @@ var Operators = map[string]*Operator{
 	"&&": {"&&", 2, 2},
 	"||": {"||", 1, 2},
 
-	"=":   {"=", math.MinInt, 2},
-	":=":  {":=", math.MinInt, 2},
-	"+=":  {"+=", math.MinInt, 2},
-	"-=":  {"-=", math.MinInt, 2},
-	"*=":  {"*=", math.MinInt, 2},
-	"/=":  {"/=", math.MinInt, 2},
-	">>=": {">>=", math.MinInt, 2},
-	"<<=": {"<<=", math.MinInt, 2},
+	"=":   {"=", math.MinInt8, 2},
+	":=":  {":=", math.MinInt8, 2},
+	"+=":  {"+=", math.MinInt8, 2},
+	"-=":  {"-=", math.MinInt8, 2},
+	"*=":  {"*=", math.MinInt8, 2},
+	"/=":  {"/=", math.MinInt8, 2},
+	">>=": {">>=", math.MinInt8, 2},
+	"<<=": {"<<=", math.MinInt8, 2},
 }
 
 func isComplete(expr *Expression) bool {
@@ -75,7 +75,7 @@ func numOperands(symbol string) int {
 	return operator.Operands
 }
 
-func precedence(symbol string) int {
+func precedence(symbol string) int8 {
 	operator, exists := Operators[symbol]
 
 	if !exists {
diff --git a/src/build/expression/Parse.go b/src/build/expression/Parse.go
index 072dfe4..ee90a0b 100644
--- a/src/build/expression/Parse.go
+++ b/src/build/expression/Parse.go
@@ -70,7 +70,7 @@ func Parse(tokens token.List) *Expression {
 				continue
 			}
 
-			group.Precedence = math.MaxInt
+			group.Precedence = math.MaxInt8
 
 			if cursor == nil {
 				cursor = group
diff --git a/src/build/expression/bench_test.go b/src/build/expression/bench_test.go
index 8287416..c447910 100644
--- a/src/build/expression/bench_test.go
+++ b/src/build/expression/bench_test.go
@@ -12,7 +12,6 @@ func BenchmarkExpression(b *testing.B) {
 	tokens := token.Tokenize(src)
 
 	for i := 0; i < b.N; i++ {
-		expr := expression.Parse(tokens)
-		expr.Close()
+		expression.Parse(tokens)
 	}
 }
diff --git a/src/build/expression/pool.go b/src/build/expression/pool.go
deleted file mode 100644
index 42b571d..0000000
--- a/src/build/expression/pool.go
+++ /dev/null
@@ -1,9 +0,0 @@
-package expression
-
-import "sync"
-
-var pool = sync.Pool{
-	New: func() interface{} {
-		return &Expression{}
-	},
-}
diff --git a/src/build/fs/File.go b/src/build/fs/File.go
index 53d49c2..d4fd1cf 100644
--- a/src/build/fs/File.go
+++ b/src/build/fs/File.go
@@ -4,6 +4,6 @@ import "git.akyoto.dev/cli/q/src/build/token"
 
 // File represents a single source file.
 type File struct {
-	Tokens token.List
 	Path   string
+	Tokens token.List
 }
diff --git a/src/build/keyword/Keyword.go b/src/build/keyword/Keyword.go
new file mode 100644
index 0000000..d3d9b18
--- /dev/null
+++ b/src/build/keyword/Keyword.go
@@ -0,0 +1,12 @@
+package keyword
+
+const (
+	Loop   = "loop"
+	Return = "return"
+)
+
+// Map is a map of all keywords used in the language.
+var Map = map[string][]byte{
+	Loop:   []byte(Loop),
+	Return: []byte(Return),
+}
diff --git a/src/build/token/Keywords.go b/src/build/token/Keywords.go
deleted file mode 100644
index d5f6231..0000000
--- a/src/build/token/Keywords.go
+++ /dev/null
@@ -1,7 +0,0 @@
-package token
-
-// Keywords defines the keywords used in the language.
-var Keywords = map[string]bool{
-	"return": true,
-	"loop":   true,
-}
diff --git a/src/build/token/Token.go b/src/build/token/Token.go
index fadf760..e10f8bc 100644
--- a/src/build/token/Token.go
+++ b/src/build/token/Token.go
@@ -6,9 +6,9 @@ import "fmt"
 // The characters that make up an identifier are grouped into a single token.
 // This makes parsing easier and allows us to do better syntax checks.
 type Token struct {
-	Kind     Kind
-	Position int
 	Bytes    []byte
+	Position int
+	Kind     Kind
 }
 
 // End returns the position after the token.
diff --git a/src/build/token/Tokenize.go b/src/build/token/Tokenize.go
index 5388b4b..7347252 100644
--- a/src/build/token/Tokenize.go
+++ b/src/build/token/Tokenize.go
@@ -1,5 +1,7 @@
 package token
 
+import "git.akyoto.dev/cli/q/src/build/keyword"
+
 // Pre-allocate these byte buffers so we can re-use them
 // instead of allocating a new buffer every time.
 var (
@@ -26,35 +28,35 @@ func Tokenize(buffer []byte) List {
 		case ' ', '\t':
 		// Separator
 		case ',':
-			tokens = append(tokens, Token{Separator, i, separatorBytes})
+			tokens = append(tokens, Token{Kind: Separator, Position: i, Bytes: separatorBytes})
 
 		// Parentheses start
 		case '(':
-			tokens = append(tokens, Token{GroupStart, i, groupStartBytes})
+			tokens = append(tokens, Token{Kind: GroupStart, Position: i, Bytes: groupStartBytes})
 
 		// Parentheses end
 		case ')':
-			tokens = append(tokens, Token{GroupEnd, i, groupEndBytes})
+			tokens = append(tokens, Token{Kind: GroupEnd, Position: i, Bytes: groupEndBytes})
 
 		// Block start
 		case '{':
-			tokens = append(tokens, Token{BlockStart, i, blockStartBytes})
+			tokens = append(tokens, Token{Kind: BlockStart, Position: i, Bytes: blockStartBytes})
 
 		// Block end
 		case '}':
-			tokens = append(tokens, Token{BlockEnd, i, blockEndBytes})
+			tokens = append(tokens, Token{Kind: BlockEnd, Position: i, Bytes: blockEndBytes})
 
 		// Array start
 		case '[':
-			tokens = append(tokens, Token{ArrayStart, i, arrayStartBytes})
+			tokens = append(tokens, Token{Kind: ArrayStart, Position: i, Bytes: arrayStartBytes})
 
 		// Array end
 		case ']':
-			tokens = append(tokens, Token{ArrayEnd, i, arrayEndBytes})
+			tokens = append(tokens, Token{Kind: ArrayEnd, Position: i, Bytes: arrayEndBytes})
 
 		// New line
 		case '\n':
-			tokens = append(tokens, Token{NewLine, i, newLineBytes})
+			tokens = append(tokens, Token{Kind: NewLine, Position: i, Bytes: newLineBytes})
 
 		// Comment
 		case '/':
@@ -66,7 +68,7 @@ func Tokenize(buffer []byte) List {
 					i++
 				}
 
-				tokens = append(tokens, Token{Operator, position, buffer[position:i]})
+				tokens = append(tokens, Token{Kind: Operator, Position: position, Bytes: buffer[position:i]})
 				continue
 			}
 
@@ -76,7 +78,7 @@ func Tokenize(buffer []byte) List {
 				i++
 			}
 
-			tokens = append(tokens, Token{Comment, position, buffer[position:i]})
+			tokens = append(tokens, Token{Kind: Comment, Position: position, Bytes: buffer[position:i]})
 			continue
 
 		// String
@@ -95,7 +97,7 @@ func Tokenize(buffer []byte) List {
 				i++
 			}
 
-			tokens = append(tokens, Token{String, start, buffer[start:end]})
+			tokens = append(tokens, Token{Kind: String, Position: start, Bytes: buffer[start:end]})
 			continue
 
 		default:
@@ -108,13 +110,15 @@ func Tokenize(buffer []byte) List {
 					i++
 				}
 
-				token := Token{Identifier, position, buffer[position:i]}
+				identifier := buffer[position:i]
+				keyword, isKeyword := keyword.Map[string(identifier)]
 
-				if Keywords[string(token.Bytes)] {
-					token.Kind = Keyword
+				if isKeyword {
+					tokens = append(tokens, Token{Kind: Keyword, Position: position, Bytes: keyword})
+				} else {
+					tokens = append(tokens, Token{Kind: Identifier, Position: position, Bytes: identifier})
 				}
 
-				tokens = append(tokens, token)
 				continue
 			}
 
@@ -127,7 +131,7 @@ func Tokenize(buffer []byte) List {
 					i++
 				}
 
-				tokens = append(tokens, Token{Number, position, buffer[position:i]})
+				tokens = append(tokens, Token{Kind: Number, Position: position, Bytes: buffer[position:i]})
 				continue
 			}
 
@@ -140,18 +144,18 @@ func Tokenize(buffer []byte) List {
 					i++
 				}
 
-				tokens = append(tokens, Token{Operator, position, buffer[position:i]})
+				tokens = append(tokens, Token{Kind: Operator, Position: position, Bytes: buffer[position:i]})
 				continue
 			}
 
 			// Invalid character
-			tokens = append(tokens, Token{Invalid, i, buffer[i : i+1]})
+			tokens = append(tokens, Token{Kind: Invalid, Position: i, Bytes: buffer[i : i+1]})
 		}
 
 		i++
 	}
 
-	tokens = append(tokens, Token{EOF, i, nil})
+	tokens = append(tokens, Token{Kind: EOF, Position: i, Bytes: nil})
 	return tokens
 }
 
diff --git a/src/errors/Error.go b/src/errors/Error.go
index ad434d3..0821e25 100644
--- a/src/errors/Error.go
+++ b/src/errors/Error.go
@@ -13,8 +13,8 @@ import (
 type Error struct {
 	Err      error
 	File     *fs.File
-	Position int
 	Stack    string
+	Position int
 }
 
 // New generates an error message at the current token position.