diff --git a/doc/grammar.bnf b/doc/grammar.bnf
index 1981507..89f7b96 100644
--- a/doc/grammar.bnf
+++ b/doc/grammar.bnf
@@ -1,11 +1,15 @@
 PROG ::= (INSTR (EOI INSTR)*)?
 INSTR ::= EXPR
-EXPR ::= TERM
+EXPR ::= IMP
+
+IMP ::= OR (imp OR)?
+OR ::= AND (or AND)*
+AND ::= TERM (and TERM)*
 
 TERM ::= FACTOR ((add | sub) FACTOR)*
 FACTOR ::= UNOP ((mul | div | mod) UNOP)*
 
-UNOP ::= (add | sub)? POW
+UNOP ::= (add | sub | not)? POW
 POW ::= GROUP (pow GROUP)?
 GROUP ::= BASE | opar EXPR cpar
-BASE ::= int
+BASE ::= int | bool
diff --git a/lib/Compiler.cpp b/lib/Compiler.cpp
index a882290..fb638d5 100644
--- a/lib/Compiler.cpp
+++ b/lib/Compiler.cpp
@@ -28,6 +28,31 @@ namespace roza
         prog->push_instr(OP_PUSH_CONST, prog->push_value(value));
       } break;
 
+      case NODE_BOOL: {
+        auto value = std::make_shared<Value>(root->repr() == "true", root->loc());
+        prog->push_instr(OP_PUSH_CONST, prog->push_value(value));
+      } break;
+
+      case NODE_IMP: {
+        compile_children(root, prog);
+        prog->push_instr(OP_IMP);
+      } break;
+
+      case NODE_AND: {
+        compile_children(root, prog);
+        prog->push_instr(OP_AND);
+      } break;
+
+      case NODE_OR: {
+        compile_children(root, prog);
+        prog->push_instr(OP_OR);
+      } break;
+
+      case NODE_NOT: {
+        compile_children(root, prog);
+        prog->push_instr(OP_NOT);
+      } break;
+
       case NODE_ADD: {
         compile_children(root, prog);
         prog->push_instr(OP_IADD);
diff --git a/lib/Lexer.cpp b/lib/Lexer.cpp
index cb2725d..4f47fcc 100644
--- a/lib/Lexer.cpp
+++ b/lib/Lexer.cpp
@@ -7,15 +7,44 @@ namespace roza
     : m_log { log }
     , m_loc { loc }
   {
+    std::vector<std::tuple<std::string, NodeType, bool>> texts = {
+      {"=>", NODE_IMP, false},
+      {"+", NODE_ADD, false},
+      {"-", NODE_SUB, false},
+      {"*", NODE_MUL, false},
+      {"/", NODE_DIV, false},
+      {"%", NODE_MOD, false},
+      {"^", NODE_POW, false},
+      {"(", NODE_OPAR, false},
+      {")", NODE_CPAR, false},
+    };
+
+    std::vector<std::tuple<std::string, NodeType, bool>> keywords = {
+      {"true", NODE_BOOL, true},
+      {"false", NODE_BOOL, true},
+      {"and", NODE_AND, false},
+      {"or", NODE_OR, false},
+      {"not", NODE_NOT, false},
+    };
+
+
     m_scanners.push_back(std::bind(&Lexer::scan_int, this));
-    m_scanners.push_back(std::bind(&Lexer::scan_text, this, "+", NODE_ADD, false));
-    m_scanners.push_back(std::bind(&Lexer::scan_text, this, "-", NODE_SUB, false));
-    m_scanners.push_back(std::bind(&Lexer::scan_text, this, "*", NODE_MUL, false));
-    m_scanners.push_back(std::bind(&Lexer::scan_text, this, "/", NODE_DIV, false));
-    m_scanners.push_back(std::bind(&Lexer::scan_text, this, "%", NODE_MOD, false));
-    m_scanners.push_back(std::bind(&Lexer::scan_text, this, "^", NODE_POW, false));
-    m_scanners.push_back(std::bind(&Lexer::scan_text, this, "(", NODE_OPAR, false));
-    m_scanners.push_back(std::bind(&Lexer::scan_text, this, ")", NODE_CPAR, false));
+
+    for (auto const& entry: keywords)
+      {
+        m_scanners.push_back(std::bind(&Lexer::scan_keyword, this,
+                                       std::get<0>(entry),
+                                       std::get<1>(entry),
+                                       std::get<2>(entry)));
+      }
+
+    for (auto const& entry: texts)
+      {
+        m_scanners.push_back(std::bind(&Lexer::scan_text, this,
+                                       std::get<0>(entry),
+                                       std::get<1>(entry),
+                                       std::get<2>(entry)));
+      }
 
   }
 
@@ -118,6 +147,18 @@ namespace roza
     return m_nodes.at(index);
   }
 
+  bool Lexer::is_sep(size_t index) const
+  {
+    if (index >= m_source.size())
+      {
+        return true;
+      }
+
+    char c = m_source[index];
+
+    return !std::isalnum(c);
+  }
+
   ScanInfo Lexer::scan_int() const
   {
     size_t cursor = m_cursor;
@@ -160,4 +201,20 @@ namespace roza
       m_cursor + text.size()
     };
   }
+
+  ScanInfo Lexer::scan_keyword(std::string const& keyword,
+                               NodeType type,
+                               bool value) const
+  {
+    auto info = scan_text(keyword, type, value);
+
+    if (is_sep(info.cursor))
+      {
+        return info;
+      }
+
+    return ScanInfo {
+    };
+  }
+
 }
diff --git a/lib/Lexer.hpp b/lib/Lexer.hpp
index f60c278..9ecc8fd 100644
--- a/lib/Lexer.hpp
+++ b/lib/Lexer.hpp
@@ -38,10 +38,16 @@ namespace roza
     std::vector<std::shared_ptr<Node>> m_nodes;
     std::vector<scanner> m_scanners;
 
+    bool is_sep(size_t index) const;
+
     ScanInfo scan_int() const;
     ScanInfo scan_text(std::string const& text,
                        NodeType type,
                        bool value=false) const;
+
+    ScanInfo scan_keyword(std::string const& keyword,
+                          NodeType type,
+                          bool value=false) const;
   };
 }
 
diff --git a/lib/Node.hpp b/lib/Node.hpp
index 8cd6acd..b7f6b49 100644
--- a/lib/Node.hpp
+++ b/lib/Node.hpp
@@ -8,7 +8,8 @@
   G(NODE_PROG), G(NODE_INSTR), G(NODE_EOI),                     \
     G(NODE_INT), G(NODE_ADD), G(NODE_SUB), G(NODE_MUL),         \
     G(NODE_DIV), G(NODE_MOD), G(NODE_POW), G(NODE_OPAR),        \
-    G(NODE_CPAR), G(NODE_UADD), G(NODE_USUB)
+    G(NODE_CPAR), G(NODE_UADD), G(NODE_USUB), G(NODE_BOOL),     \
+    G(NODE_AND), G(NODE_OR), G(NODE_NOT), G(NODE_IMP)
 
 namespace roza
 {
diff --git a/lib/Parser.cpp b/lib/Parser.cpp
index d77ed7c..21ab5cd 100644
--- a/lib/Parser.cpp
+++ b/lib/Parser.cpp
@@ -126,7 +126,52 @@ namespace roza
 
   std::shared_ptr<Node> Parser::parse_expr()
   {
-    return parse_term();
+    return parse_imp();
+  }
+
+  std::shared_ptr<Node> Parser::parse_imp()
+  {
+    auto lhs = parse_or();
+
+    if (type_is(NODE_IMP))
+      {
+        auto root = consume();
+        root->add_child(lhs);
+        root->add_child(parse_or());
+        lhs = root;
+      }
+
+    return lhs;
+  }
+
+  std::shared_ptr<Node> Parser::parse_or()
+  {
+    auto lhs = parse_and();
+
+    while (type_is(NODE_OR))
+      {
+        auto root = consume();
+        root->add_child(lhs);
+        root->add_child(parse_and());
+        lhs = root;
+      }
+
+    return lhs;
+  }
+
+  std::shared_ptr<Node> Parser::parse_and()
+  {
+    auto lhs = parse_term();
+
+    while (type_is(NODE_AND))
+      {
+        auto root = consume();
+        root->add_child(lhs);
+        root->add_child(parse_term());
+        lhs = root;
+      }
+
+    return lhs;
   }
 
   std::shared_ptr<Node> Parser::parse_term()
@@ -181,6 +226,15 @@ namespace roza
         return root;
       }
 
+    if (type_is(NODE_NOT))
+      {
+        auto root = std::make_shared<Node>(NODE_NOT, "", m_lexer.loc());
+        next();
+
+        root->add_child(parse_pow());
+        return root;
+      }
+
     return parse_pow();
   }
 
@@ -214,7 +268,18 @@ namespace roza
 
   std::shared_ptr<Node> Parser::parse_base()
   {
-    return parse_int();
+    if (type_is(NODE_INT)
+        || type_is(NODE_BOOL))
+      {
+        return consume();
+      }
+
+    m_log.fatal(node()->loc(),
+                "unknown node '"
+                + node()->string()
+                + "'");
+
+    return nullptr;
   }
 
   std::shared_ptr<Node> Parser::parse_int()
diff --git a/lib/Parser.hpp b/lib/Parser.hpp
index e7d50c0..95f396d 100644
--- a/lib/Parser.hpp
+++ b/lib/Parser.hpp
@@ -32,6 +32,9 @@ namespace roza
     std::shared_ptr<Node> parse_prog();
     std::shared_ptr<Node> parse_instr();
     std::shared_ptr<Node> parse_expr();
+    std::shared_ptr<Node> parse_imp();
+    std::shared_ptr<Node> parse_or();
+    std::shared_ptr<Node> parse_and();
     std::shared_ptr<Node> parse_term();
     std::shared_ptr<Node> parse_factor();
     std::shared_ptr<Node> parse_unop();
diff --git a/lib/StaticPass.cpp b/lib/StaticPass.cpp
index 6121632..1123e36 100644
--- a/lib/StaticPass.cpp
+++ b/lib/StaticPass.cpp
@@ -19,7 +19,25 @@ namespace roza
 
     switch (root->type())
       {
-      case NODE_INT: break;
+      case NODE_INT:
+      case NODE_BOOL:
+        break;
+
+      case NODE_IMP:
+      case NODE_OR:
+      case NODE_AND: {
+        check_children(root);
+        auto lhs = resolver.find(root->child(0));
+        auto rhs = resolver.find(root->child(1));
+        check_types(root, lhs, std::make_shared<Type>(TY_BOOL));
+        check_types(root, lhs, rhs);
+      } break;
+
+      case NODE_NOT: {
+        check_children(root);
+        auto lhs = resolver.find(root->child(0));
+        check_types(root, lhs, std::make_shared<Type>(TY_BOOL));
+      } break;
 
       case NODE_ADD:
       case NODE_SUB:
@@ -27,35 +45,74 @@ namespace roza
       case NODE_DIV:
       case NODE_MOD:
       case NODE_POW: {
+        check_children(root);
         auto lhs = resolver.find(root->child(0));
         auto rhs = resolver.find(root->child(1));
-
-        if (!lhs->equals(*rhs))
-          {
-            m_log.fatal(root->loc(),
-                        std::string()
-                        + "type mismatch, expected '"
-                        + lhs->string()
-                        + "', got '"
-                        + rhs->string()
-                        + "'");
-          }
-
+        check_types(root, lhs, std::make_shared<Type>(TY_INT));
+        check_types(root, lhs, rhs);
       } break;
 
       case NODE_UADD:
       case NODE_USUB: {
+        check_children(root);
       } break;
 
       case NODE_PROG: {
-        for (size_t i=0; i<root->size(); i++)
-          {
-            check(root->child(i));
-          }
+        check_children(root);
       } break;
 
       default:
         m_log.fatal(root->loc(), "cannot check node '" + root->string() + "'");
       }
   }
+
+  void StaticPass::check_children(std::shared_ptr<Node> root)
+  {
+    for (size_t i=0; i<root->size(); i++)
+      {
+        check(root->child(i));
+      }
+  }
+
+  void StaticPass::check_types(std::shared_ptr<Node> root,
+                               std::shared_ptr<Type> lhs,
+                               std::shared_ptr<Type> rhs)
+  {
+    if (!lhs->equals(*rhs))
+      {
+        m_log.fatal(root->loc(),
+                    std::string()
+                    + "type mismatch, expected '"
+                    + lhs->string()
+                    + "', got '"
+                    + rhs->string()
+                    + "'");
+      }
+  }
+
+  void StaticPass::check_types(std::shared_ptr<Node> root,
+                               std::shared_ptr<Type> lhs,
+                               std::vector<std::shared_ptr<Type>> const& rhs)
+  {
+    for (auto const& ty: rhs)
+      {
+        if (lhs->equals(*ty))
+          {
+            return;
+          }
+      }
+
+    std::stringstream ss;
+
+    ss << "type mismatch, got '" << lhs->string() << "'";
+    ss << "candidates are:" << std::endl;
+
+    for (auto ty: rhs)
+      {
+        ss << "\t-> " << ty->string() << std::endl;
+      }
+
+    m_log.fatal(root->loc(), ss.str());
+  }
+
 }
diff --git a/lib/StaticPass.hpp b/lib/StaticPass.hpp
index e62b0bf..5697b6c 100644
--- a/lib/StaticPass.hpp
+++ b/lib/StaticPass.hpp
@@ -4,6 +4,7 @@
 #include "commons.hpp"
 #include "StatusLog.hpp"
 #include "Node.hpp"
+#include "Type.hpp"
 
 namespace roza
 {
@@ -14,9 +15,18 @@ namespace roza
     virtual ~StaticPass();
 
     void check(std::shared_ptr<Node> root);
+    void check_children(std::shared_ptr<Node> root);
 
   private:
     StatusLog& m_log;
+
+    void check_types(std::shared_ptr<Node> root,
+                     std::shared_ptr<Type> lhs,
+                     std::shared_ptr<Type> rhs);
+
+    void check_types(std::shared_ptr<Node> root,
+                     std::shared_ptr<Type> lhs,
+                     std::vector<std::shared_ptr<Type>> const& rhs);
   };
 }
 
diff --git a/lib/Type.hpp b/lib/Type.hpp
index 28280da..efbbb6d 100644
--- a/lib/Type.hpp
+++ b/lib/Type.hpp
@@ -4,7 +4,7 @@
 #include "commons.hpp"
 
 #define BASE_TYPE(G) \
-  G(TY_INT)
+  G(TY_INT), G(TY_BOOL)
 
 namespace roza
 {
diff --git a/lib/TypeResolver.cpp b/lib/TypeResolver.cpp
index 8a0c213..bff5878 100644
--- a/lib/TypeResolver.cpp
+++ b/lib/TypeResolver.cpp
@@ -23,6 +23,14 @@ namespace roza
         return std::make_shared<Type>(BaseType::TY_INT);
       } break;
 
+      case NODE_IMP:
+      case NODE_AND:
+      case NODE_OR:
+      case NODE_NOT:
+      case NODE_BOOL: {
+        return std::make_shared<Type>(BaseType::TY_BOOL);
+      } break;
+
       case NODE_ADD:
       case NODE_SUB:
       case NODE_MUL:
diff --git a/lib/VM.cpp b/lib/VM.cpp
index cefcf82..b7484d7 100644
--- a/lib/VM.cpp
+++ b/lib/VM.cpp
@@ -25,6 +25,37 @@ namespace roza
             m_pc++;
           } break;
 
+          case OP_IMP: {
+            apply_binop(program, [](auto lhs, auto rhs){
+              bool a = lhs->as_bool();
+              bool b = rhs->as_bool();
+
+              return std::make_shared<Value>(!a || b,
+                                             lhs->loc());
+            });
+          } break;
+
+          case OP_AND: {
+            apply_binop(program, [](auto lhs, auto rhs){
+              return std::make_shared<Value>(lhs->as_bool() && rhs->as_bool(),
+                                             lhs->loc());
+            });
+          } break;
+
+          case OP_OR: {
+            apply_binop(program, [](auto lhs, auto rhs){
+              return std::make_shared<Value>(lhs->as_bool() || rhs->as_bool(),
+                                             lhs->loc());
+            });
+          } break;
+
+          case OP_NOT: {
+            apply_unop(program, [](auto lhs){
+              return std::make_shared<Value>(!lhs->as_bool(),
+                                             lhs->loc());
+            });
+          } break;
+
           case OP_IADD: {
             apply_binop(program, [](auto lhs, auto rhs){
               return std::make_shared<Value>(lhs->as_int() + rhs->as_int(),
@@ -62,7 +93,8 @@ namespace roza
 
           case OP_IPOW: {
             apply_binop(program, [](auto lhs, auto rhs){
-              return std::make_shared<Value>(std::pow(lhs->as_int(), rhs->as_int()),
+              return std::make_shared<Value>(static_cast<int>(std::pow(lhs->as_int(),
+                                                                       rhs->as_int())),
                                              lhs->loc());
             });
           } break;
diff --git a/lib/Value.cpp b/lib/Value.cpp
index 51d5648..6661bdf 100644
--- a/lib/Value.cpp
+++ b/lib/Value.cpp
@@ -9,6 +9,13 @@ namespace roza
   {
   }
 
+  /*explicit*/ Value::Value(bool value, SrcLoc loc)
+    : m_type { std::make_shared<Type>(BaseType::TY_BOOL) }
+    , m_bool_val { value }
+    , m_loc { loc }
+  {
+  }
+
   /*virtual*/ Value::~Value()
   {
   }
@@ -20,6 +27,11 @@ namespace roza
         return std::to_string(m_int_val);
       }
 
+    if (m_type->equals(TY_BOOL))
+      {
+        return m_bool_val ? "true" : "false";
+      }
+
     assert("cannot stringify unknown value " && 0);
   }
 }
diff --git a/lib/Value.hpp b/lib/Value.hpp
index 16521da..2e15f1a 100644
--- a/lib/Value.hpp
+++ b/lib/Value.hpp
@@ -11,16 +11,21 @@ namespace roza
   {
   public:
     explicit Value(int value, SrcLoc loc);
+    explicit Value(bool value, SrcLoc loc);
     virtual ~Value();
 
     SrcLoc loc() const { return m_loc; }
+
     int as_int() const { return m_int_val; }
+    bool as_bool() const { return m_bool_val; }
+
     std::shared_ptr<Type> type() const { return m_type; }
     std::string string() const;
 
   private:
     std::shared_ptr<Type> m_type;
     int m_int_val;
+    bool m_bool_val;
     SrcLoc m_loc;
   };
 }
diff --git a/lib/opcodes.hpp b/lib/opcodes.hpp
index 5664fd0..dd0348a 100644
--- a/lib/opcodes.hpp
+++ b/lib/opcodes.hpp
@@ -7,7 +7,8 @@
   G(OP_PUSH_CONST), \
     G(OP_POP), \
     G(OP_IADD), G(OP_ISUB), G(OP_IMUL), G(OP_IDIV), G(OP_IMOD), G(OP_IPOW), \
-    G(OP_MOD), G(OP_IUADD), G(OP_IUSUB),
+    G(OP_MOD), G(OP_IUADD), G(OP_IUSUB), G(OP_AND), G(OP_OR), G(OP_NOT), \
+    G(OP_IMP)
 
 namespace roza
 {
diff --git a/tests/Lexer.cpp b/tests/Lexer.cpp
index 2c0cb6c..3c59794 100644
--- a/tests/Lexer.cpp
+++ b/tests/Lexer.cpp
@@ -55,3 +55,25 @@ TEST_CASE_METHOD(LexerTest, "Lexer_int_arith")
   REQUIRE("CPAR" == get_str(7));
   REQUIRE("" == get_str(8));
 }
+
+TEST_CASE_METHOD(LexerTest, "Lexer_keywords")
+{
+  REQUIRE_THROWS(m_lexer.scan(" andor "));
+  REQUIRE_NOTHROW(m_lexer.scan(" and+ "));
+  REQUIRE_NOTHROW(m_lexer.scan(" (and) "));
+}
+
+TEST_CASE_METHOD(LexerTest, "Lexer_bool")
+{
+  SECTION("nominal cases")
+    {
+      m_lexer.scan("and or not true false =>");
+      REQUIRE("AND" == get_str(0));
+      REQUIRE("OR" == get_str(1));
+      REQUIRE("NOT" == get_str(2));
+      REQUIRE("BOOL[true]" == get_str(3));
+      REQUIRE("BOOL[false]" == get_str(4));
+      REQUIRE("IMP" == get_str(5));
+      REQUIRE("" == get_str(6));
+    }
+}
diff --git a/tests/Parser.cpp b/tests/Parser.cpp
index 938564d..d794ec8 100644
--- a/tests/Parser.cpp
+++ b/tests/Parser.cpp
@@ -70,3 +70,24 @@ TEST_CASE_METHOD(ParserTest, "Parser_int_arith")
 
   test_node("PROG(USUB(POW(INT[2],INT[7])))", " -2^7 ");
 }
+
+TEST_CASE_METHOD(ParserTest, "Parser_bool")
+{
+  test_node("PROG(BOOL[true])",
+            "true");
+
+  test_node("PROG(AND(BOOL[true],BOOL[false]))",
+            "true and false");
+
+  test_node("PROG(OR(BOOL[true],BOOL[false]))",
+            "true or false");
+
+  test_node("PROG(NOT(BOOL[false]))",
+            "not false");
+
+  test_node("PROG(NOT(OR(BOOL[false],BOOL[true])))",
+              "not (false or true)");
+
+  test_node("PROG(IMP(BOOL[true],BOOL[false]))",
+              "true => false");
+}
diff --git a/tests/StaticPass.cpp b/tests/StaticPass.cpp
index 52e7a2a..d713a1b 100644
--- a/tests/StaticPass.cpp
+++ b/tests/StaticPass.cpp
@@ -33,4 +33,5 @@ protected:
 TEST_CASE_METHOD(StaticPassTest, "StaticPass_integer")
 {
   test_ok(" 43 ");
+  test_ko(" 43 + 7 * true");
 }