diff --git a/src/chalk.cr b/src/chalk.cr
index 4fd5248..548ef4e 100644
--- a/src/chalk.cr
+++ b/src/chalk.cr
@@ -1,12 +1,12 @@
 require "./chalk/*"
 
 module Chalk
-    lexer = Lexer.new
-    parser = Parser.new
+  lexer = Lexer.new
+  parser = Parser.new
 
-    tokens = lexer.lex(File.read("test.txt"))
-    trees = parser.parse?(tokens)
-    trees.try do |trees|
-        trees.each &.accept(PrintVisitor.new)
-    end
+  tokens = lexer.lex(File.read("test.txt"))
+  trees = parser.parse?(tokens)
+  trees.try do |trees|
+    trees.each &.accept(PrintVisitor.new)
+  end
 end
diff --git a/src/chalk/builder.cr b/src/chalk/builder.cr
index 4cdd103..43dec6c 100644
--- a/src/chalk/builder.cr
+++ b/src/chalk/builder.cr
@@ -2,37 +2,37 @@ require "./lexer.cr"
 require "./parsers.cr"
 
 module Chalk
-    module Builder
-        def type(type): BasicParser(Token)
-            return TypeParser.new(type).as(BasicParser(Token))
-        end
-
-        def char(type): BasicParser(Token)
-            return CharParser.new(type).as(BasicParser(Token))
-        end
-
-        def transform(parser : BasicParser(T), &transform : T -> R) forall T, R
-            return TransformParser.new(parser, &transform).as(BasicParser(R))
-        end
-
-        def optional(parser : BasicParser(T)): BasicParser(T?) forall T
-            return OptionalParser.new(parser).as(BasicParser(T?))
-        end
-
-        def either(*args : BasicParser(T)): BasicParser(T) forall T
-            return EitherParser.new(args.to_a).as(BasicParser(T))
-        end
-
-        def many(parser : BasicParser(T)): BasicParser(Array(T)) forall T
-            return ManyParser.new(parser).as(BasicParser(Array(T)))
-        end
-
-        def delimited(parser : BasicParser(T), delimiter : BasicParser(R)): BasicParser(Array(T)) forall T, R
-            return DelimitedParser.new(parser, delimiter).as(BasicParser(Array(T)))
-        end
-
-        def then(first : BasicParser(T), second : BasicParser(R)) forall T, R
-            return NextParser.new(first, second).as(BasicParser(Array(T | R)))
-        end
+  module Builder
+    def type(type) : BasicParser(Token)
+      return TypeParser.new(type).as(BasicParser(Token))
     end
+
+    def char(type) : BasicParser(Token)
+      return CharParser.new(type).as(BasicParser(Token))
+    end
+
+    def transform(parser : BasicParser(T), &transform : T -> R) forall T, R
+      return TransformParser.new(parser, &transform).as(BasicParser(R))
+    end
+
+    def optional(parser : BasicParser(T)) : BasicParser(T?) forall T
+      return OptionalParser.new(parser).as(BasicParser(T?))
+    end
+
+    def either(*args : BasicParser(T)) : BasicParser(T) forall T
+      return EitherParser.new(args.to_a).as(BasicParser(T))
+    end
+
+    def many(parser : BasicParser(T)) : BasicParser(Array(T)) forall T
+      return ManyParser.new(parser).as(BasicParser(Array(T)))
+    end
+
+    def delimited(parser : BasicParser(T), delimiter : BasicParser(R)) : BasicParser(Array(T)) forall T, R
+      return DelimitedParser.new(parser, delimiter).as(BasicParser(Array(T)))
+    end
+
+    def then(first : BasicParser(T), second : BasicParser(R)) forall T, R
+      return NextParser.new(first, second).as(BasicParser(Array(T | R)))
+    end
+  end
 end
diff --git a/src/chalk/lexer.cr b/src/chalk/lexer.cr
index 9923f4f..0d3124c 100644
--- a/src/chalk/lexer.cr
+++ b/src/chalk/lexer.cr
@@ -1,82 +1,82 @@
 require "lex"
 
 module Chalk
-    enum TokenType
-        Any,
-        Str,
-        Id,
-        LitDec,
-        LitBin,
-        LitHex,
-        OpAdd
-        OpSub
-        OpMul
-        OpDiv
-        OpOr
-        OpAnd
-        OpXor
-        KwSprite
-        KwInline
-        KwFun
-        KwU0
-        KwU8
-        KwU12
-        KwVar
-        KwIf
-        KwElse
-        KwWhile
-        KwReturn
+  enum TokenType
+    Any,
+    Str,
+    Id,
+    LitDec,
+    LitBin,
+    LitHex,
+    OpAdd
+    OpSub
+    OpMul
+    OpDiv
+    OpOr
+    OpAnd
+    OpXor
+    KwSprite
+    KwInline
+    KwFun
+    KwU0
+    KwU8
+    KwU12
+    KwVar
+    KwIf
+    KwElse
+    KwWhile
+    KwReturn
+  end
+
+  class Token
+    def initialize(@string : String, @type : TokenType)
     end
 
-    class Token
-        def initialize(@string : String, @type : TokenType)
-        end
+    getter string : String
+    getter type : TokenType
+  end
 
-        getter string : String
-        getter type : TokenType
+  class Lexer
+    def initialize
+      @lexer = Lex::Lexer.new
+      @lexer.add_pattern(".", TokenType::Any.value)
+      @lexer.add_pattern("\"(\\\\\"|[^\"])*\"",
+        TokenType::Str.value)
+      @lexer.add_pattern("[a-zA-Z_][a-zA-Z_0-9]*",
+        TokenType::Id.value)
+      @lexer.add_pattern("[0-9]+",
+        TokenType::LitDec.value)
+      @lexer.add_pattern("0b[0-1]+",
+        TokenType::LitBin.value)
+      @lexer.add_pattern("0x[0-9a-fA-F]+",
+        TokenType::LitHex.value)
+      @lexer.add_pattern("\\+", TokenType::OpAdd.value)
+      @lexer.add_pattern("-", TokenType::OpSub.value)
+      @lexer.add_pattern("\\*", TokenType::OpMul.value)
+      @lexer.add_pattern("/", TokenType::OpDiv.value)
+      @lexer.add_pattern("&", TokenType::OpAdd.value)
+      @lexer.add_pattern("\\|", TokenType::OpOr.value)
+      @lexer.add_pattern("^", TokenType::OpXor.value)
+      @lexer.add_pattern("sprite", TokenType::KwSprite.value)
+      @lexer.add_pattern("inline", TokenType::KwInline.value)
+      @lexer.add_pattern("fun", TokenType::KwFun.value)
+      @lexer.add_pattern("u0", TokenType::KwU0.value)
+      @lexer.add_pattern("u8", TokenType::KwU8.value)
+      @lexer.add_pattern("u12", TokenType::KwU12.value)
+      @lexer.add_pattern("var", TokenType::KwVar.value)
+      @lexer.add_pattern("if", TokenType::KwIf.value)
+      @lexer.add_pattern("else", TokenType::KwElse.value)
+      @lexer.add_pattern("while", TokenType::KwWhile.value)
+      @lexer.add_pattern("return", TokenType::KwReturn.value)
     end
 
-    class Lexer
-        def initialize
-            @lexer = Lex::Lexer.new
-            @lexer.add_pattern(".", TokenType::Any.value)
-            @lexer.add_pattern("\"(\\\\\"|[^\"])*\"",
-                               TokenType::Str.value)
-            @lexer.add_pattern("[a-zA-Z_][a-zA-Z_0-9]*",
-                               TokenType::Id.value)
-            @lexer.add_pattern("[0-9]+",
-                               TokenType::LitDec.value)
-            @lexer.add_pattern("0b[0-1]+",
-                               TokenType::LitBin.value)
-            @lexer.add_pattern("0x[0-9a-fA-F]+",
-                               TokenType::LitHex.value)
-            @lexer.add_pattern("\\+", TokenType::OpAdd.value)
-            @lexer.add_pattern("-", TokenType::OpSub.value)
-            @lexer.add_pattern("\\*", TokenType::OpMul.value)
-            @lexer.add_pattern("/", TokenType::OpDiv.value)
-            @lexer.add_pattern("&", TokenType::OpAdd.value)
-            @lexer.add_pattern("\\|", TokenType::OpOr.value)
-            @lexer.add_pattern("^", TokenType::OpXor.value)
-            @lexer.add_pattern("sprite", TokenType::KwSprite.value)
-            @lexer.add_pattern("inline", TokenType::KwInline.value)
-            @lexer.add_pattern("fun", TokenType::KwFun.value)
-            @lexer.add_pattern("u0", TokenType::KwU0.value)
-            @lexer.add_pattern("u8", TokenType::KwU8.value)
-            @lexer.add_pattern("u12", TokenType::KwU12.value)
-            @lexer.add_pattern("var", TokenType::KwVar.value)
-            @lexer.add_pattern("if", TokenType::KwIf.value)
-            @lexer.add_pattern("else", TokenType::KwElse.value)
-            @lexer.add_pattern("while", TokenType::KwWhile.value)
-            @lexer.add_pattern("return", TokenType::KwReturn.value)
-        end
-
-        def lex(string)
-            return @lexer.lex(string)
-                .select { |t| !t[0][0].whitespace? }
-                .map do |tuple|
-                    string, id = tuple
-                    Token.new(string, TokenType.new(id))
-                end
+    def lex(string)
+      return @lexer.lex(string)
+        .select { |t| !t[0][0].whitespace? }
+        .map do |tuple|
+          string, id = tuple
+          Token.new(string, TokenType.new(id))
         end
     end
+  end
 end
diff --git a/src/chalk/parser.cr b/src/chalk/parser.cr
index 7fb5e2b..5075788 100644
--- a/src/chalk/parser.cr
+++ b/src/chalk/parser.cr
@@ -1,173 +1,173 @@
 require "./builder.cr"
 
 module Chalk
-    class Parser
-        include Builder
+  class Parser
+    include Builder
 
-        private def create_type
-            either(type(TokenType::KwU0), type(TokenType::KwU8), type(TokenType::KwU12))
-        end
-
-        private def create_lit
-            dec_parser = type(TokenType::LitDec).transform &.string.to_i64
-            hex_parser = type(TokenType::LitHex).transform &.string.lchop("0x").to_i64(16)
-            bin_parser = type(TokenType::LitBin).transform &.string.lchop("0b").to_i64(2)
-            lit_parser = either(dec_parser, hex_parser, bin_parser).transform { |it| TreeLit.new(it).as(Tree) }
-            return lit_parser
-        end
-
-        private def create_op_expr(atom, op)
-            pl = PlaceholderParser(Tree).new
-            recurse = atom.then(op).then(pl).transform do |arr|
-                arr = arr.flatten
-                TreeOp.new(
-                    arr[1].as(Token).type,
-                    arr[0].as(Tree),
-                    arr[2].as(Tree)).as(Tree)
-            end
-            pl.parser = either(recurse, atom)
-            return pl
-        end
-
-        private def create_op_exprs(atom, ops)
-            ops.reduce(atom) do |previous, current|
-                create_op_expr(previous, current)
-            end
-        end
-
-        private def create_call(expr)
-            call = type(TokenType::Id).then(char '(').then(delimited(expr, char ',')).then(char ')').transform do |arr|
-                arr = arr.flatten
-                name = arr[0].as(Token).string
-                params = arr[2..arr.size - 2].map &.as(Tree)
-                TreeCall.new(name, params).as(Tree)
-            end
-            return call
-        end
-
-        private def create_expr
-            expr_place = PlaceholderParser(Tree).new
-            literal = create_lit
-            id = type(TokenType::Id).transform { |it| TreeId.new(it.string).as(Tree) }
-            call = create_call(expr_place)
-            atom = either(literal, call, id)
-
-            ops = [ either(type(TokenType::OpMul), type(TokenType::OpDiv)),
-                    either(type(TokenType::OpAdd), type(TokenType::OpSub)),
-                    type(TokenType::OpXor),
-                    type(TokenType::OpAnd),
-                    type(TokenType::OpOr) ]
-            expr = create_op_exprs(atom, ops)
-            expr_place.parser = expr
-
-            return expr
-        end
-
-        private def create_var(expr)
-            var = type(TokenType::KwVar).then(type(TokenType::Id)).then(char '=').then(expr).then(char ';').transform do |arr|
-                arr = arr.flatten
-                name = arr[1].as(Token).string
-                exp = arr[arr.size - 2].as(Tree)
-                TreeVar.new(name, exp).as(Tree)
-            end
-            return var
-        end
-
-        private def create_assign(expr)
-            assign = type(TokenType::Id).then(char '=').then(expr).then(char ';').transform do |arr|
-                arr = arr.flatten
-                name = arr[0].as(Token).string
-                exp = arr[arr.size - 2].as(Tree)
-                TreeAssign.new(name, exp).as(Tree)
-            end
-            return assign
-        end
-
-        private def create_basic(expr)
-            basic = expr.then(char ';').transform do |arr|
-                arr.flatten[0].as(Tree)
-            end
-            return basic
-        end
-
-        private def create_if(expr, block)
-            iff = type(TokenType::KwIf).then(char '(').then(expr).then(char ')').then(block)
-                .then(optional(type(TokenType::KwElse).then(block)))
-                .transform do |arr|
-                arr = arr.flatten
-                cond = arr[2].as(Tree)
-                code = arr[4].as(Tree)
-                otherwise = arr.size == 7 ? arr[6].as(Tree) : nil
-                TreeIf.new(cond, code, otherwise).as(Tree)
-            end
-            return iff
-        end
-
-        private def create_while(expr, block)
-            whilee = type(TokenType::KwWhile).then(char '(').then(expr).then(char ')').then(block).transform do |arr|
-                arr = arr.flatten
-                cond = arr[2].as(Tree)
-                code = arr[4].as(Tree)
-                TreeWhile.new(cond, code).as(Tree)
-            end
-            return whilee
-        end
-
-        private def create_return(expr)
-            returnn = type(TokenType::KwReturn).then(expr).then(char ';').transform do |arr|
-                arr = arr.flatten
-                value = arr[1].as(Tree)
-                TreeReturn.new(value).as(Tree)
-            end
-            return returnn
-        end
-
-        private def create_block(statement)
-            block = char('{').then(many(statement)).then(char '}').transform do |arr|
-                arr = arr.flatten
-                params = arr[1..arr.size - 2].map &.as(Tree)
-                TreeBlock.new(params).as(Tree)
-            end
-            return block
-        end
-
-        private def create_statement_block
-            statement_place = PlaceholderParser(Tree).new
-            expr = create_expr
-            block = create_block(statement_place)
-            iff = create_if(expr, block)
-            whilee = create_while(expr, block)
-            returnn = create_return(expr)
-            var = create_var(expr)
-            assign = create_assign(expr)
-            basic = create_basic(expr)
-            statement = either(basic, var, assign, block, iff, whilee, returnn)
-            statement_place.parser = statement
-            return {statement, block}
-        end
-
-        private def create_func(block, type)
-            func = type(TokenType::KwFun).then(type(TokenType::Id))
-                .then(char '(').then(delimited(type(TokenType::Id), char ',')).then(char ')')
-                .then(char ':').then(type)
-                .then(block).transform do |arr|
-                arr = arr.flatten
-                name = arr[1].as(Token).string
-                params = arr[3..arr.size - 5].map &.as(Token).string
-                code = arr[arr.size - 1].as(Tree)
-                type = arr[arr.size - 2].as(Token).type
-                TreeFunction.new(name, params, code).as(Tree)
-            end
-            return func
-        end
-
-        def initialize
-            _, block = create_statement_block
-            @parser = many(create_func(block, create_type)).as(BasicParser(Array(Tree)))
-        end
-
-        def parse?(tokens)
-            return @parser.parse?(tokens, 0).try &.[0]
-        end
+    private def create_type
+      either(type(TokenType::KwU0), type(TokenType::KwU8), type(TokenType::KwU12))
     end
+
+    private def create_lit
+      dec_parser = type(TokenType::LitDec).transform &.string.to_i64
+      hex_parser = type(TokenType::LitHex).transform &.string.lchop("0x").to_i64(16)
+      bin_parser = type(TokenType::LitBin).transform &.string.lchop("0b").to_i64(2)
+      lit_parser = either(dec_parser, hex_parser, bin_parser).transform { |it| TreeLit.new(it).as(Tree) }
+      return lit_parser
+    end
+
+    private def create_op_expr(atom, op)
+      pl = PlaceholderParser(Tree).new
+      recurse = atom.then(op).then(pl).transform do |arr|
+        arr = arr.flatten
+        TreeOp.new(
+          arr[1].as(Token).type,
+          arr[0].as(Tree),
+          arr[2].as(Tree)).as(Tree)
+      end
+      pl.parser = either(recurse, atom)
+      return pl
+    end
+
+    private def create_op_exprs(atom, ops)
+      ops.reduce(atom) do |previous, current|
+        create_op_expr(previous, current)
+      end
+    end
+
+    private def create_call(expr)
+      call = type(TokenType::Id).then(char '(').then(delimited(expr, char ',')).then(char ')').transform do |arr|
+        arr = arr.flatten
+        name = arr[0].as(Token).string
+        params = arr[2..arr.size - 2].map &.as(Tree)
+        TreeCall.new(name, params).as(Tree)
+      end
+      return call
+    end
+
+    private def create_expr
+      expr_place = PlaceholderParser(Tree).new
+      literal = create_lit
+      id = type(TokenType::Id).transform { |it| TreeId.new(it.string).as(Tree) }
+      call = create_call(expr_place)
+      atom = either(literal, call, id)
+
+      ops = [either(type(TokenType::OpMul), type(TokenType::OpDiv)),
+             either(type(TokenType::OpAdd), type(TokenType::OpSub)),
+             type(TokenType::OpXor),
+             type(TokenType::OpAnd),
+             type(TokenType::OpOr)]
+      expr = create_op_exprs(atom, ops)
+      expr_place.parser = expr
+
+      return expr
+    end
+
+    private def create_var(expr)
+      var = type(TokenType::KwVar).then(type(TokenType::Id)).then(char '=').then(expr).then(char ';').transform do |arr|
+        arr = arr.flatten
+        name = arr[1].as(Token).string
+        exp = arr[arr.size - 2].as(Tree)
+        TreeVar.new(name, exp).as(Tree)
+      end
+      return var
+    end
+
+    private def create_assign(expr)
+      assign = type(TokenType::Id).then(char '=').then(expr).then(char ';').transform do |arr|
+        arr = arr.flatten
+        name = arr[0].as(Token).string
+        exp = arr[arr.size - 2].as(Tree)
+        TreeAssign.new(name, exp).as(Tree)
+      end
+      return assign
+    end
+
+    private def create_basic(expr)
+      basic = expr.then(char ';').transform do |arr|
+        arr.flatten[0].as(Tree)
+      end
+      return basic
+    end
+
+    private def create_if(expr, block)
+      iff = type(TokenType::KwIf).then(char '(').then(expr).then(char ')').then(block)
+        .then(optional(type(TokenType::KwElse).then(block)))
+        .transform do |arr|
+          arr = arr.flatten
+          cond = arr[2].as(Tree)
+          code = arr[4].as(Tree)
+          otherwise = arr.size == 7 ? arr[6].as(Tree) : nil
+          TreeIf.new(cond, code, otherwise).as(Tree)
+        end
+      return iff
+    end
+
+    private def create_while(expr, block)
+      whilee = type(TokenType::KwWhile).then(char '(').then(expr).then(char ')').then(block).transform do |arr|
+        arr = arr.flatten
+        cond = arr[2].as(Tree)
+        code = arr[4].as(Tree)
+        TreeWhile.new(cond, code).as(Tree)
+      end
+      return whilee
+    end
+
+    private def create_return(expr)
+      returnn = type(TokenType::KwReturn).then(expr).then(char ';').transform do |arr|
+        arr = arr.flatten
+        value = arr[1].as(Tree)
+        TreeReturn.new(value).as(Tree)
+      end
+      return returnn
+    end
+
+    private def create_block(statement)
+      block = char('{').then(many(statement)).then(char '}').transform do |arr|
+        arr = arr.flatten
+        params = arr[1..arr.size - 2].map &.as(Tree)
+        TreeBlock.new(params).as(Tree)
+      end
+      return block
+    end
+
+    private def create_statement_block
+      statement_place = PlaceholderParser(Tree).new
+      expr = create_expr
+      block = create_block(statement_place)
+      iff = create_if(expr, block)
+      whilee = create_while(expr, block)
+      returnn = create_return(expr)
+      var = create_var(expr)
+      assign = create_assign(expr)
+      basic = create_basic(expr)
+      statement = either(basic, var, assign, block, iff, whilee, returnn)
+      statement_place.parser = statement
+      return {statement, block}
+    end
+
+    private def create_func(block, type)
+      func = type(TokenType::KwFun).then(type(TokenType::Id))
+        .then(char '(').then(delimited(type(TokenType::Id), char ',')).then(char ')')
+        .then(char ':').then(type)
+        .then(block).transform do |arr|
+          arr = arr.flatten
+          name = arr[1].as(Token).string
+          params = arr[3..arr.size - 5].map &.as(Token).string
+          code = arr[arr.size - 1].as(Tree)
+          type = arr[arr.size - 2].as(Token).type
+          TreeFunction.new(name, params, code).as(Tree)
+        end
+      return func
+    end
+
+    def initialize
+      _, block = create_statement_block
+      @parser = many(create_func(block, create_type)).as(BasicParser(Array(Tree)))
+    end
+
+    def parse?(tokens)
+      return @parser.parse?(tokens, 0).try &.[0]
+    end
+  end
 end
diff --git a/src/chalk/parsers.cr b/src/chalk/parsers.cr
index 2fd029e..8d530a7 100644
--- a/src/chalk/parsers.cr
+++ b/src/chalk/parsers.cr
@@ -1,151 +1,149 @@
 require "./builder.cr"
 
 module Chalk
+  abstract class BasicParser(T)
+    abstract def parse?(tokens : Array(Token),
+                        index : Int64) : Tuple(T, Int64)?
 
-    abstract class BasicParser(T)
-        abstract def parse?(tokens : Array(Token),
-                           index : Int64): Tuple(T, Int64)?
-        def parse(tokens : Array(Token),
-                  index : Int64): Tuple(T, Int64)
-            return parse?(tokens, index).not_nil!
-        end
-
-        def transform(&transform : T -> R) forall R
-            return TransformParser.new(self, &transform).as(BasicParser(R))
-        end
-
-        def then(other : BasicParser(R)): BasicParser(Array(T | R)) forall R
-            return NextParser
-                .new(self, other)
-                .as(BasicParser(Array(T | R)))
-        end
+    def parse(tokens : Array(Token),
+              index : Int64) : Tuple(T, Int64)
+      return parse?(tokens, index).not_nil!
     end
 
-    class TypeParser < BasicParser(Token)
-        def initialize(@type : TokenType)
-        end
-
-        def parse?(tokens, index)
-            return nil unless index < tokens.size
-            return nil unless tokens[index].type == @type
-            return { tokens[index], index + 1}
-        end
+    def transform(&transform : T -> R) forall R
+      return TransformParser.new(self, &transform).as(BasicParser(R))
     end
 
-    class CharParser < BasicParser(Token)
-        def initialize(@char : Char)
-        end
+    def then(other : BasicParser(R)) : BasicParser(Array(T | R)) forall R
+      return NextParser.new(self, other).as(BasicParser(Array(T | R)))
+    end
+  end
 
-        def parse?(tokens, index)
-            return nil unless index < tokens.size
-            return nil unless (tokens[index].type == TokenType::Any) &&
-                tokens[index].string[0] == @char
-            return { tokens[index], index + 1}
-        end
+  class TypeParser < BasicParser(Token)
+    def initialize(@type : TokenType)
     end
 
-    class TransformParser(T, R) < BasicParser(R)
-        def initialize(@parser : BasicParser(T), &@block : T -> R)
-        end
+    def parse?(tokens, index)
+      return nil unless index < tokens.size
+      return nil unless tokens[index].type == @type
+      return {tokens[index], index + 1}
+    end
+  end
 
-        def parse?(tokens, index)
-            if parsed = @parser.parse?(tokens, index)
-                return { @block.call(parsed[0]), parsed[1] }
-            end
-            return nil
-        end
+  class CharParser < BasicParser(Token)
+    def initialize(@char : Char)
     end
 
-    class OptionalParser(T) < BasicParser(T?)
-        def initialize(@parser : BasicParser(T))
-        end
+    def parse?(tokens, index)
+      return nil unless index < tokens.size
+      return nil unless (tokens[index].type == TokenType::Any) &&
+                        tokens[index].string[0] == @char
+      return {tokens[index], index + 1}
+    end
+  end
 
-        def parse?(tokens, index)
-            if parsed = @parser.parse?(tokens, index)
-                return { parsed[0], parsed[1] }
-            end
-            return { nil, index }
-        end
+  class TransformParser(T, R) < BasicParser(R)
+    def initialize(@parser : BasicParser(T), &@block : T -> R)
     end
 
-    class EitherParser(T) < BasicParser(T)
-        def initialize(@parsers : Array(BasicParser(T)))
-        end
+    def parse?(tokens, index)
+      if parsed = @parser.parse?(tokens, index)
+        return {@block.call(parsed[0]), parsed[1]}
+      end
+      return nil
+    end
+  end
 
-        def parse?(tokens, index)
-            @parsers.each do |parser|
-                if parsed = parser.parse?(tokens, index)
-                    return parsed
-                end
-            end
-            return nil
-        end
+  class OptionalParser(T) < BasicParser(T?)
+    def initialize(@parser : BasicParser(T))
     end
 
-    class ManyParser(T) < BasicParser(Array(T))
-        def initialize(@parser : BasicParser(T))
-        end
+    def parse?(tokens, index)
+      if parsed = @parser.parse?(tokens, index)
+        return {parsed[0], parsed[1]}
+      end
+      return {nil, index}
+    end
+  end
 
-        def parse?(tokens, index)
-            many = [] of T
-            while parsed = @parser.parse?(tokens, index)
-                item, index = parsed
-                many << item
-            end
-            return { many, index }
-        end
+  class EitherParser(T) < BasicParser(T)
+    def initialize(@parsers : Array(BasicParser(T)))
     end
 
-    class DelimitedParser(T, R) < BasicParser(Array(T))
-        def initialize(@parser : BasicParser(T), @delimiter : BasicParser(R))
+    def parse?(tokens, index)
+      @parsers.each do |parser|
+        if parsed = parser.parse?(tokens, index)
+          return parsed
         end
+      end
+      return nil
+    end
+  end
 
-        def parse?(tokens, index)
-            array = [] of T
-            first = @parser.parse?(tokens, index)
-            return { array, index } unless first
-            first_value, index = first
-            array << first_value
-            while delimiter = @delimiter.parse?(tokens, index)
-                _, new_index = delimiter
-                new = @parser.parse?(tokens, new_index)
-                break unless new
-                new_value, index = new
-                array << new_value
-            end
-
-            return { array, index }
-        end
+  class ManyParser(T) < BasicParser(Array(T))
+    def initialize(@parser : BasicParser(T))
     end
 
-    class NextParser(T, R) < BasicParser(Array(T | R))
-        def initialize(@first : BasicParser(T), @second : BasicParser(R))
-        end
+    def parse?(tokens, index)
+      many = [] of T
+      while parsed = @parser.parse?(tokens, index)
+        item, index = parsed
+        many << item
+      end
+      return {many, index}
+    end
+  end
 
-        def parse?(tokens, index)
-            first = @first.parse?(tokens, index)
-            return nil unless first
-            first_value, index = first
-            
-            second = @second.parse?(tokens, index)
-            return nil unless second
-            second_value, index = second
-
-            array = Array(T | R).new
-            array << first_value << second_value
-            return { array, index }
-        end
+  class DelimitedParser(T, R) < BasicParser(Array(T))
+    def initialize(@parser : BasicParser(T), @delimiter : BasicParser(R))
     end
 
-    class PlaceholderParser(T) < BasicParser(T)
-        property parser : BasicParser(T)?
+    def parse?(tokens, index)
+      array = [] of T
+      first = @parser.parse?(tokens, index)
+      return {array, index} unless first
+      first_value, index = first
+      array << first_value
+      while delimiter = @delimiter.parse?(tokens, index)
+        _, new_index = delimiter
+        new = @parser.parse?(tokens, new_index)
+        break unless new
+        new_value, index = new
+        array << new_value
+      end
 
-        def initialize
-            @parser = nil
-        end
-
-        def parse?(tokens, index)
-            @parser.try &.parse?(tokens, index)
-        end
+      return {array, index}
     end
+  end
+
+  class NextParser(T, R) < BasicParser(Array(T | R))
+    def initialize(@first : BasicParser(T), @second : BasicParser(R))
+    end
+
+    def parse?(tokens, index)
+      first = @first.parse?(tokens, index)
+      return nil unless first
+      first_value, index = first
+
+      second = @second.parse?(tokens, index)
+      return nil unless second
+      second_value, index = second
+
+      array = Array(T | R).new
+      array << first_value << second_value
+      return {array, index}
+    end
+  end
+
+  class PlaceholderParser(T) < BasicParser(T)
+    property parser : BasicParser(T)?
+
+    def initialize
+      @parser = nil
+    end
+
+    def parse?(tokens, index)
+      @parser.try &.parse?(tokens, index)
+    end
+  end
 end
diff --git a/src/chalk/print_visitor.cr b/src/chalk/print_visitor.cr
index bb82050..0356ab8 100644
--- a/src/chalk/print_visitor.cr
+++ b/src/chalk/print_visitor.cr
@@ -1,53 +1,53 @@
 require "./tree.cr"
 
 module Chalk
-    class PrintVisitor < Visitor
-        def initialize
-            @indent = 0
-        end
+  class PrintVisitor < Visitor
+    def initialize
+      @indent = 0
+    end
 
-        def print_indent
-            @indent.times do
-                STDOUT << "  "
-            end
-        end
+    def print_indent
+      @indent.times do
+        STDOUT << "  "
+      end
+    end
 
-        def visit(id : TreeId)
-            print_indent
-            puts id.id
-        end
+    def visit(id : TreeId)
+      print_indent
+      puts id.id
+    end
 
-        def visit(lit : TreeLit)
-            print_indent
-            puts lit.lit
-        end
+    def visit(lit : TreeLit)
+      print_indent
+      puts lit.lit
+    end
 
-        def visit(op : TreeOp)
-            print_indent
-            STDOUT << "[op] "
-            puts op.op
-            @indent += 1
-        end
+    def visit(op : TreeOp)
+      print_indent
+      STDOUT << "[op] "
+      puts op.op
+      @indent += 1
+    end
 
-        def finish(op : TreeOp)
-            @indent -= 1
-        end
+    def finish(op : TreeOp)
+      @indent -= 1
+    end
 
-        def visit(function : TreeFunction)
-            print_indent
-            STDOUT << "[function] " << function.name << "( "
-            function.params.each do |param|
-                STDOUT << param << " "
-            end
-            puts ")"
-            @indent += 1
-        end
+    def visit(function : TreeFunction)
+      print_indent
+      STDOUT << "[function] " << function.name << "( "
+      function.params.each do |param|
+        STDOUT << param << " "
+      end
+      puts ")"
+      @indent += 1
+    end
 
-        def finish(function : TreeFunction)
-            @indent -= 1
-        end
+    def finish(function : TreeFunction)
+      @indent -= 1
+    end
 
-        macro forward(text, type)
+    macro forward(text, type)
             def visit(tree : {{type}})
                 print_indent
                 puts {{text}}
@@ -59,12 +59,12 @@ module Chalk
             end
         end
 
-        forward("[call]", TreeCall)
-        forward("[block]", TreeBlock)
-        forward("[var]", TreeVar)
-        forward("[assign]", TreeAssign)
-        forward("[if]", TreeIf)
-        forward("[while]", TreeWhile)
-        forward("[return]", TreeReturn)
-    end
+    forward("[call]", TreeCall)
+    forward("[block]", TreeBlock)
+    forward("[var]", TreeVar)
+    forward("[assign]", TreeAssign)
+    forward("[if]", TreeIf)
+    forward("[while]", TreeWhile)
+    forward("[return]", TreeReturn)
+  end
 end
diff --git a/src/chalk/tree.cr b/src/chalk/tree.cr
index 6ce35d8..3bc5874 100644
--- a/src/chalk/tree.cr
+++ b/src/chalk/tree.cr
@@ -1,138 +1,159 @@
 module Chalk
-    class Visitor
-        def visit(tree : Tree)
-        end
-
-        def finish(tree : Tree)
-        end
+  class Visitor
+    def visit(tree : Tree)
     end
 
-    class Tree
-        def accept(v : Visitor)
-            v.visit(self)
-            v.finish(self)
-        end
+    def finish(tree : Tree)
+    end
+  end
+
+  class Tree
+    def accept(v : Visitor)
+      v.visit(self)
+      v.finish(self)
+    end
+  end
+
+  class TreeId < Tree
+    property id : String
+
+    def initialize(@id : String)
+    end
+  end
+
+  class TreeLit < Tree
+    property lit : Int64
+
+    def initialize(@lit : Int64)
+    end
+  end
+
+  class TreeCall < Tree
+    property name : String
+    property params : Array(Tree)
+
+    def initialize(@name : String, @params : Array(Tree))
     end
 
-    class TreeId < Tree
-        property id : String
-        def initialize(@id : String) end
+    def accept(v : Visitor)
+      v.visit(self)
+      @params.each &.accept(v)
+      v.finish(self)
+    end
+  end
+
+  class TreeOp < Tree
+    property op : TokenType
+    property left : Tree
+    property right : Tree
+
+    def initialize(@op : TokenType, @left : Tree, @right : Tree)
     end
 
-    class TreeLit < Tree
-        property lit : Int64
-        def initialize(@lit : Int64) end
+    def accept(v : Visitor)
+      v.visit(self)
+      @left.accept(v)
+      @right.accept(v)
+      v.finish(self)
+    end
+  end
+
+  class TreeBlock < Tree
+    def initialize(@children : Array(Tree))
     end
 
-    class TreeCall < Tree
-        property name : String
-        property params : Array(Tree)
+    def accept(v : Visitor)
+      v.visit(self)
+      @children.each &.accept(v)
+      v.finish(self)
+    end
+  end
 
-        def initialize(@name : String, @params : Array(Tree)) end
-        def accept(v : Visitor)
-            v.visit(self)
-            @params.each &.accept(v)
-            v.finish(self)
-        end
+  class TreeFunction < Tree
+    property name : String
+    property params : Array(String)
+    property block : Tree
+
+    def initialize(@name : String, @params : Array(String), @block : Tree)
     end
 
-    class TreeOp < Tree
-        property op : TokenType
-        property left : Tree
-        property right : Tree
-        def initialize(@op : TokenType, @left : Tree, @right : Tree) end
+    def accept(v : Visitor)
+      v.visit(self)
+      @block.accept(v)
+      v.finish(self)
+    end
+  end
 
-        def accept(v : Visitor)
-            v.visit(self)
-            @left.accept(v)
-            @right.accept(v)
-            v.finish(self)
-        end
+  class TreeVar < Tree
+    property name : String
+    property expr : Tree
+
+    def initialize(@name : String, @expr : Tree)
     end
 
-    class TreeBlock < Tree
-        def initialize(@children : Array(Tree)) end
+    def accept(v : Visitor)
+      v.visit(self)
+      @expr.accept(v)
+      v.finish(self)
+    end
+  end
 
-        def accept(v : Visitor)
-            v.visit(self)
-            @children.each &.accept(v)
-            v.finish(self)
-        end
+  class TreeAssign < Tree
+    property name : String
+    property expr : Tree
+
+    def initialize(@name : String, @expr : Tree)
     end
 
-    class TreeFunction < Tree
-        property name : String
-        property params : Array(String)
-        property block : Tree
+    def accept(v : Visitor)
+      v.visit(self)
+      @expr.accept(v)
+      v.finish(self)
+    end
+  end
 
-        def initialize(@name : String, @params : Array(String), @block : Tree) end
-        def accept(v : Visitor)
-            v.visit(self)
-            @block.accept(v)
-            v.finish(self)
-        end
+  class TreeIf < Tree
+    property condition : Tree
+    property block : Tree
+    property otherwise : Tree?
+
+    def initialize(@condition : Tree, @block : Tree, @otherwise : Tree? = nil)
     end
 
-    class TreeVar < Tree
-        property name : String
-        property expr : Tree
+    def accept(v : Visitor)
+      v.visit(self)
+      @condition.accept(v)
+      @block.accept(v)
+      @otherwise.try &.accept(v)
+      v.finish(self)
+    end
+  end
 
-        def initialize(@name : String, @expr : Tree) end
-        def accept(v : Visitor)
-            v.visit(self)
-            @expr.accept(v)
-            v.finish(self)
-        end
+  class TreeWhile < Tree
+    property condition : Tree
+    property block : Tree
+
+    def initialize(@condition : Tree, @block : Tree)
     end
 
-    class TreeAssign < Tree
-        property name : String
-        property expr : Tree
+    def accept(v : Visitor)
+      v.visit(self)
+      @condition.accept(v)
+      @block.accept(v)
+      v.finish(self)
+    end
+  end
 
-        def initialize(@name : String, @expr : Tree) end
-        def accept(v : Visitor)
-            v.visit(self)
-            @expr.accept(v)
-            v.finish(self)
-        end
+  class TreeReturn < Tree
+    property rvalue : Tree
+
+    def initialize(@rvalue : Tree)
     end
 
-    class TreeIf < Tree
-        property condition : Tree
-        property block : Tree
-        property otherwise : Tree?
-
-        def initialize(@condition : Tree, @block : Tree, @otherwise : Tree? = nil) end
-        def accept(v : Visitor)
-            v.visit(self)
-            @condition.accept(v)
-            @block.accept(v)
-            @otherwise.try &.accept(v)
-            v.finish(self)
-        end
-    end
-
-    class TreeWhile < Tree
-        property condition : Tree
-        property block : Tree
-
-        def initialize(@condition : Tree, @block : Tree) end
-        def accept(v : Visitor)
-            v.visit(self)
-            @condition.accept(v)
-            @block.accept(v)
-            v.finish(self)
-        end
-    end
-
-    class TreeReturn < Tree
-        property rvalue : Tree
-        
-        def initialize(@rvalue : Tree) end
-        def accept(v : Visitor)
-            v.visit(self)
-            @rvalue.accept(v)
-            v.finish(self)
-        end
+    def accept(v : Visitor)
+      v.visit(self)
+      @rvalue.accept(v)
+      v.finish(self)
     end
+  end
 end