diff --git a/CMakeLists.txt b/CMakeLists.txt
index 215a0ab..1fa0eeb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -6,7 +6,8 @@ set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
 set(CMAKE_CXX_STANDARD 17)
 
 find_package(Boost COMPONENTS program_options REQUIRED)
-find_package(FLEX)
+find_package(FLEX REQUIRED)
+find_package(BISON REQUIRED)
 include_directories(${Boost_INCLUDE_DIR})
 
 FLEX_TARGET(scanner source/scanner.l ${CMAKE_CURRENT_BINARY_DIR}/scanner.cpp)
@@ -26,3 +27,20 @@ add_executable(elna cli/main.cpp
 )
 target_include_directories(elna PRIVATE include)
 target_link_libraries(elna LINK_PUBLIC ${Boost_LIBRARIES})
+
+FLEX_TARGET(lexer parser/lexer.ll ${CMAKE_CURRENT_BINARY_DIR}/lexer.cpp)
+BISON_TARGET(parser parser/parser.yy ${CMAKE_CURRENT_BINARY_DIR}/parser.cpp)
+add_flex_bison_dependency(lexer parser)
+
+add_executable(test parser/main.cpp
+	source/lexer.cpp include/elna/source/lexer.hpp
+	source/parser.cpp include/elna/source/parser.hpp
+	source/types.cpp include/elna/source/types.hpp
+	source/symbol_table.cpp include/elna/source/symbol_table.hpp
+	source/result.cpp include/elna/source/result.hpp
+	source/semantic.cpp include/elna/source/semantic.hpp
+	source/optimizer.cpp include/elna/source/optimizer.hpp
+	${BISON_parser_OUTPUTS} ${FLEX_lexer_OUTPUTS}
+)
+target_include_directories(test PRIVATE ${CMAKE_CURRENT_BINARY_DIR} parser include)
+# target_link_libraries(test ${FLEX_LIBRARIES})
diff --git a/parser/lexer.ll b/parser/lexer.ll
new file mode 100644
index 0000000..9485abd
--- /dev/null
+++ b/parser/lexer.ll
@@ -0,0 +1,131 @@
+%{
+#define YY_NO_UNISTD_H
+#define YY_USER_ACTION this->location.columns(yyleng);
+
+#include <sstream>
+#include "parser.hpp"
+
+#undef YY_DECL
+#define YY_DECL yy::parser::symbol_type elna::syntax::FooLexer::lex()
+#define yyterminate() return yy::parser::make_YYEOF(this->location)
+%}
+
+%option c++ noyywrap never-interactive
+%option yyclass="elna::syntax::FooLexer"
+
+%%
+%{
+    this->location.step();
+%}
+
+\-\-.*                  {
+                            /* Skip the comment */
+                        }
+[\ \t\r]                ; /* Skip the whitespaces */
+\n+                     {
+                            this->location.lines(yyleng);
+                            this->location.step();
+                        }
+if                      {
+                            return yy::parser::make_IF(this->location);
+                        }
+then                    {
+                            return yy::parser::make_THEN(this->location);
+                        }
+while                   {
+                            return yy::parser::make_WHILE(this->location);
+                        }
+do                      {
+                            return yy::parser::make_DO(this->location);
+                        }
+proc                    {
+                            return yy::parser::make_PROCEDURE(this->location);
+                        }
+begin                   {
+                            return yy::parser::make_BEGIN_BLOCK(this->location);
+                        }
+end                     {
+                            return yy::parser::make_END_BLOCK(this->location);
+                        }
+const                   {
+                            return yy::parser::make_CONST(this->location);
+                        }
+var                     {
+                            return yy::parser::make_VAR(this->location);
+                        }
+True                    {
+                            return yy::parser::make_BOOLEAN(true, this->location);
+                        }
+False                   {
+                            return yy::parser::make_BOOLEAN(false, this->location);
+                        }
+[A-Za-z_][A-Za-z0-9_]*  {
+                            return yy::parser::make_IDENTIFIER(yytext, this->location);
+                        }
+[0-9]+                  {
+                            return yy::parser::make_NUMBER(strtol(yytext, NULL, 10), this->location);
+                        }
+\(                      {
+                            return yy::parser::make_LEFT_PAREN(this->location);
+                        }
+\)                      {
+                            return yy::parser::make_RIGHT_PAREN(this->location);
+                        }
+\>=                     {
+                            return yy::parser::make_GREATER_EQUAL(this->location);
+                        }
+\<=                     {
+                            return yy::parser::make_LESS_EQUAL(this->location);
+                        }
+\>                      {
+                            return yy::parser::make_GREATER_THAN(this->location);
+                        }
+\<                      {
+                            return yy::parser::make_LESS_THAN(this->location);
+                        }
+\/=                     {
+                            return yy::parser::make_NOT_EQUAL(this->location);
+                        }
+=                       {
+                            return yy::parser::make_EQUALS(this->location);
+                        }
+;                       {
+                            return yy::parser::make_SEMICOLON(this->location);
+                        }
+\.                      {
+                            return yy::parser::make_DOT(this->location);
+                        }
+,                       {
+                            return yy::parser::make_COMMA(this->location);
+                        }
+\+                      {
+                            return yy::parser::make_PLUS(this->location);
+                        }
+\-                      {
+                            return yy::parser::make_MINUS(this->location);
+                        }
+\*                      {
+                            return yy::parser::make_MULTIPLICATION(this->location);
+                        }
+\/                      {
+                            return yy::parser::make_DIVISION(this->location);
+                        }
+:=                      {
+                            return yy::parser::make_ASSIGNMENT(this->location);
+                        }
+:                       {
+                            return yy::parser::make_COLON(this->location);
+                        }
+\^                      {
+                            return yy::parser::make_HAT(this->location);
+                        }
+@                       {
+                            return yy::parser::make_AT(this->location);
+                        }
+.                       {
+                            std::stringstream ss;
+
+                            ss << "Illegal character 0x" << std::hex << static_cast<unsigned char>(yytext[0]);
+                            throw yy::parser::syntax_error(this->location, ss.str());
+                        }
+%%
diff --git a/parser/main.cpp b/parser/main.cpp
new file mode 100644
index 0000000..2c51302
--- /dev/null
+++ b/parser/main.cpp
@@ -0,0 +1,46 @@
+#include "parser.hpp"
+#include <iostream>
+#include <sstream>
+
+int main()
+{
+    std::istringstream inp(
+            "const world = 5, hello = 7;\n"
+            "var x: Int, y: ^Int;\n"
+            "begin\n"
+            "end.\n"
+    );
+    std::unique_ptr<elna::source::program> program;
+    int result{ 1 };
+
+    elna::syntax::FooLexer lexer(inp);
+    yy::parser parser(lexer, program);
+    try
+    {
+        result = parser();
+    }
+    catch (yy::parser::syntax_error& syntax_error)
+    {
+        std::cerr << syntax_error.location << ": " << syntax_error.what() << std::endl;
+        return result;
+    }
+
+    for (auto& definition : program->definitions())
+    {
+        auto const_definition = dynamic_cast<elna::source::constant_definition *>(definition.get());
+
+        std::cout << "const " << const_definition->identifier() << " = "
+            << const_definition->body().number() << std::endl;
+    }
+    for (auto& declaration : program->declarations())
+    {
+        std::cout << "var " << declaration->identifier() << ": ";
+
+        if (declaration->type().is_pointer())
+        {
+            std::cout << '^';
+        }
+        std::cout << declaration->type().base() << std::endl;
+    }
+    return result;
+}
diff --git a/parser/parser.yy b/parser/parser.yy
new file mode 100644
index 0000000..bf692e5
--- /dev/null
+++ b/parser/parser.yy
@@ -0,0 +1,406 @@
+%require "3.2"
+%language "c++"
+
+%code requires {
+    #include <cstdint>
+    #include "elna/source/parser.hpp"
+
+
+    #if ! defined(yyFlexLexerOnce)
+        #include <FlexLexer.h>
+    #endif
+
+    namespace elna::syntax
+    {
+    class FooLexer;
+    }
+}
+
+%code provides {
+    namespace elna::syntax
+    {
+
+    class FooLexer : public yyFlexLexer
+    {
+    public:
+        yy::location location;
+
+        FooLexer(std::istream& arg_yyin)
+            : yyFlexLexer(&arg_yyin)
+        {
+        }
+
+        yy::parser::symbol_type lex();
+    };
+
+    }
+}
+
+%define api.token.raw
+%define api.token.constructor
+%define api.value.type variant
+%define parse.assert
+
+%parse-param {elna::syntax::FooLexer& lexer}
+%parse-param {std::unique_ptr<elna::source::program>& program}
+%locations
+
+%header
+
+%code {
+    #define yylex lexer.lex
+}
+%start program;
+
+%token <std::string> IDENTIFIER "identifier"
+%token <std::int32_t> NUMBER "number"
+%token <bool> BOOLEAN
+%token IF THEN WHILE DO
+%token CONST VAR PROCEDURE
+%token BEGIN_BLOCK END_BLOCK
+%token TRUE FALSE
+%token LEFT_PAREN RIGHT_PAREN SEMICOLON DOT COMMA
+%token GREATER_EQUAL LESS_EQUAL LESS_THAN GREATER_THAN NOT_EQUAL EQUALS
+%token PLUS MINUS MULTIPLICATION DIVISION
+%token ASSIGNMENT COLON HAT AT
+
+%type <std::unique_ptr<elna::source::integer_literal>> integer_literal;
+%type <std::unique_ptr<elna::source::boolean_literal>> boolean_literal;
+%type <std::unique_ptr<elna::source::variable_expression>> variable_expression;
+%type <std::unique_ptr<elna::source::constant_definition>> constant_definition;
+%type <std::unique_ptr<elna::source::unary_expression>> reference_expression dereference_expression;
+%type <std::vector<std::unique_ptr<elna::source::constant_definition>>> constant_definition_part constant_definitions;
+%type <std::unique_ptr<elna::source::type_expression>> type_expression;
+%type <std::unique_ptr<elna::source::declaration>> variable_declaration;
+%type <std::vector<std::unique_ptr<elna::source::declaration>>> variable_declaration_part variable_declarations;
+%type <std::unique_ptr<elna::source::assign_statement>> assign_statement;
+%type <std::unique_ptr<elna::source::expression>> expression factor term comparand;
+%type <std::unique_ptr<elna::source::statement>> statement;
+%type <std::vector<std::unique_ptr<elna::source::expression>>> arguments;
+%type <std::unique_ptr<elna::source::call_statement>> call_statement;
+%type <std::unique_ptr<elna::source::compound_statement>> compound_statement;
+%type <std::vector<std::unique_ptr<elna::source::statement>>> statements;
+%type <std::unique_ptr<elna::source::if_statement>> if_statement;
+%type <std::unique_ptr<elna::source::while_statement>> while_statement;
+%type <std::unique_ptr<elna::source::procedure_definition>> procedure_definition;
+%type <std::vector<std::unique_ptr<elna::source::procedure_definition>>> procedure_definition_part procedure_definitions;
+%%
+program: constant_definition_part variable_declaration_part procedure_definition_part statement DOT
+        {
+            elna::source::position position;
+            std::vector<std::unique_ptr<elna::source::definition>> definitions($1.size());
+            std::vector<std::unique_ptr<elna::source::declaration>> declarations($2.size());
+            std::vector<std::unique_ptr<elna::source::definition>>::iterator definition = definitions.begin();
+            std::vector<std::unique_ptr<elna::source::declaration>>::iterator declaration = declarations.begin();
+
+            for (auto& constant : $1)
+            {
+                *definition++ = std::move(constant);
+            }
+            for (auto& variable : $2)
+            {
+                *declaration++ = std::move(variable);
+            }
+            program = std::make_unique<elna::source::program>(position,
+                 std::move(definitions), std::move(declarations), std::move($4));
+        }
+procedure_definition:
+    PROCEDURE IDENTIFIER SEMICOLON constant_definition_part variable_declaration_part statement SEMICOLON
+        {
+            elna::source::position position;
+            std::vector<std::unique_ptr<elna::source::definition>> definitions($4.size());
+            std::vector<std::unique_ptr<elna::source::declaration>> declarations($5.size());
+            std::vector<std::unique_ptr<elna::source::definition>>::iterator definition = definitions.begin();
+            std::vector<std::unique_ptr<elna::source::declaration>>::iterator declaration = declarations.begin();
+
+            for (auto& constant : $4)
+            {
+                *definition++ = std::move(constant);
+            }
+            for (auto& variable : $5)
+            {
+                *declaration++ = std::move(variable);
+            }
+            auto block = std::make_unique<elna::source::block>(position,
+                 std::move(definitions), std::move(declarations), std::move($6));
+            $$ = std::make_unique<elna::source::procedure_definition>(position,
+                $2, std::move(block));
+        }
+procedure_definition_part:
+    /* no procedure definitions. */ {}
+    | procedure_definitions { std::swap($1, $$); }
+procedure_definitions:
+    procedure_definition procedure_definitions
+        {
+            std::swap($$, $2);
+            $$.emplace($$.cbegin(), std::move($1));
+        }
+    | procedure_definition { $$.emplace_back(std::move($1)); }
+integer_literal: NUMBER
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::integer_literal>(position, $1); 
+        }
+boolean_literal: BOOLEAN
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::boolean_literal>(position, $1);
+        }
+variable_expression: IDENTIFIER
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::variable_expression>(position, $1);
+        }
+reference_expression: AT variable_expression
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::unary_expression>(position, std::move($2), '@');
+        }
+dereference_expression: factor HAT
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::unary_expression>(position, std::move($1), '^');
+        }
+expression:
+    comparand EQUALS comparand
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::binary_expression>(position,
+                std::move($1), std::move($3), '=');
+        }
+    | comparand NOT_EQUAL comparand
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::binary_expression>(position,
+                std::move($1), std::move($3), 'n');
+        }
+    | comparand GREATER_THAN comparand
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::binary_expression>(position,
+                std::move($1), std::move($3), '>');
+        }
+    | comparand LESS_THAN comparand
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::binary_expression>(position,
+                std::move($1), std::move($3), '<');
+        }
+    | comparand GREATER_EQUAL comparand
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::binary_expression>(position,
+                std::move($1), std::move($3), 'g');
+        }
+    | comparand LESS_EQUAL comparand
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::binary_expression>(position,
+                std::move($1), std::move($3), 'l');
+        }
+comparand:
+    term PLUS term
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::binary_expression>(position,
+                std::move($1), std::move($3), '+');
+        }
+    | term MINUS term
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::binary_expression>(position,
+                std::move($1), std::move($3), '-');
+        }
+    | term { $$ = std::move($1); }
+factor:
+    integer_literal { $$ = std::move($1); }
+    | boolean_literal { $$ = std::move($1); }
+    | variable_expression { $$ = std::move($1); }
+    | reference_expression { $$ = std::move($1); }
+    | dereference_expression { $$ = std::move($1); }
+    | LEFT_PAREN expression RIGHT_PAREN { $$ = std::move($2); }
+term:
+    factor MULTIPLICATION factor
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::binary_expression>(position,
+                std::move($1), std::move($3), '*');
+        }
+    | factor DIVISION factor
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::binary_expression>(position,
+                std::move($1), std::move($3), '/');
+        }
+    | factor { $$ = std::move($1); }
+type_expression:
+    HAT IDENTIFIER
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::type_expression>(position, $2, true);
+        }
+    | IDENTIFIER
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::type_expression>(position, $1, false);
+        }
+assign_statement: IDENTIFIER ASSIGNMENT expression
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@2.begin.column)
+            };
+            $$ = std::make_unique<elna::source::assign_statement>(position, $1, std::move($3));
+        }
+call_statement: IDENTIFIER LEFT_PAREN arguments RIGHT_PAREN
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::call_statement>(position, $1);
+            std::swap($3, $$->arguments());
+        }
+compound_statement: BEGIN_BLOCK statements END_BLOCK
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::compound_statement>(position);
+            std::swap($2, $$->statements());
+        }
+if_statement: IF expression THEN statement
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::if_statement>(position,
+                std::move($2), std::move($4));
+        }
+while_statement: WHILE expression DO statement
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::while_statement>(position,
+                std::move($2), std::move($4));
+        }
+statement:
+    assign_statement { $$ = std::move($1); }
+    | call_statement { $$ = std::move($1); }
+    | compound_statement { $$ = std::move($1); }
+    | if_statement { $$ = std::move($1); }
+    | while_statement { $$ = std::move($1); }
+variable_declaration: IDENTIFIER COLON type_expression
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::declaration>(position, $1, std::move($3));
+        }
+variable_declarations:
+    variable_declaration COMMA variable_declarations
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), std::move($1));
+        }
+    | variable_declaration { $$.emplace_back(std::move($1)); }
+constant_definition: IDENTIFIER EQUALS integer_literal
+        {
+            elna::source::position position{
+                static_cast<std::size_t>(@1.begin.line),
+                static_cast<std::size_t>(@1.begin.column)
+            };
+            $$ = std::make_unique<elna::source::constant_definition>(position,
+                $1, std::move($3)); 
+        };
+constant_definitions:
+    constant_definition COMMA constant_definitions
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), std::move($1));
+        }
+    | constant_definition { $$.emplace_back(std::move($1)); }
+constant_definition_part:
+    /* no constant definitions */ {}
+    | CONST constant_definitions SEMICOLON { std::swap($$, $2); };
+variable_declaration_part:
+    /* no constant declarations */ {}
+    | VAR variable_declarations SEMICOLON { std::swap($$, $2); };
+arguments:
+    /* no arguments */ {}
+    | expression COMMA arguments
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), std::move($1));
+        }
+    | expression { $$.emplace_back(std::move($1)); }
+statements:
+    /* no statements */ {}
+    | statement SEMICOLON statements
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), std::move($1));
+        }
+    | statement { $$.emplace_back(std::move($1)); }
+%%
+
+void yy::parser::error(const location_type& loc, const std::string &message)
+{
+    throw yy::parser::syntax_error(loc, message);
+}
diff --git a/tests/empty_file.eln b/tests/empty_file.eln
new file mode 100644
index 0000000..e69de29
diff --git a/tests/failures/empty_file.txt b/tests/failures/empty_file.txt
new file mode 100644
index 0000000..e69de29