diff --git a/samples/test.brc b/samples/test.brc
index b2f978b..02f3f71 100644
--- a/samples/test.brc
+++ b/samples/test.brc
@@ -49,10 +49,10 @@ i u32 <- 0, rep text[i] != 0:
 ;*/
 
 main fun -> u32
-    num1 u8 <- 42
-    num2 s8 <- -15
+    /*num1 u8 <- 42
+    num2 s8 <- 3 - +15
     num3 u32 <- 1234123
-    num4 s32 <- -345345
+    num4 s32 <- -345345*/
     num5 r32 <- -42.58
 
     ret 0
diff --git a/src/Compiler/ModuleBuilder.cpp b/src/Compiler/ModuleBuilder.cpp
index ca59586..5a8c3c7 100644
--- a/src/Compiler/ModuleBuilder.cpp
+++ b/src/Compiler/ModuleBuilder.cpp
@@ -11,6 +11,7 @@
 #include "Parser/Expression/ExpressionCall.h"
 #include "Parser/Expression/ExpressionIfElse.h"
 #include "Parser/Expression/ExpressionBinary.h"
+#include "Parser/Expression/ExpressionUnary.h"
 #include "Parser/Expression/ExpressionBlock.h"
 
 #include "Parser/Statement/StatementFunction.h"
@@ -172,6 +173,8 @@ void ModuleBuilder::buildVarDeclaration(shared_ptr<StatementVariable> statement)
         }
     } else {
         llvm::Value *value = valueForExpression(statement->getExpression());
+        if (value == nullptr)
+            return;
         llvm::AllocaInst *alloca = builder->CreateAlloca(typeForValueType(statement->getValueType(), 0), nullptr, statement->getName());
 
         if (!setAlloca(statement->getName(), alloca))
@@ -297,6 +300,8 @@ llvm::Value *ModuleBuilder::valueForExpression(shared_ptr<Expression> expression
             return valueForExpression(dynamic_pointer_cast<ExpressionGrouping>(expression)->getExpression());
         case ExpressionKind::BINARY:
             return valueForBinary(dynamic_pointer_cast<ExpressionBinary>(expression));
+        case ExpressionKind::UNARY:
+            return valueForUnary(dynamic_pointer_cast<ExpressionUnary>(expression));
         case ExpressionKind::IF_ELSE:
             return valueForIfElse(dynamic_pointer_cast<ExpressionIfElse>(expression));
         case ExpressionKind::VAR:
@@ -337,7 +342,7 @@ llvm::Value *ModuleBuilder::valueForLiteral(shared_ptr<ExpressionLiteral> expres
         case ValueTypeKind::S32:
             return llvm::ConstantInt::get(typeS32, expression->getS32Value(), true);
         case ValueTypeKind::R32:
-            return llvm::ConstantInt::get(typeR32, expression->getR32Value(), true);
+            return llvm::ConstantFP::get(typeR32, expression->getR32Value());
     }
 }
 
@@ -383,7 +388,7 @@ llvm::Value *ModuleBuilder::valueForBinaryBool(ExpressionBinaryOperation operati
     case ExpressionBinaryOperation::NOT_EQUAL:
         return builder->CreateICmpNE(leftValue, rightValue);
     default:
-        markError(0, 0, "Unexpecgted operation for boolean operands");
+        markError(0, 0, "Unexpected operation for boolean operands");
         return nullptr;
     }
 }
@@ -469,6 +474,26 @@ llvm::Value *ModuleBuilder::valueForBinaryReal(ExpressionBinaryOperation operati
     }
 }
 
+llvm::Value *ModuleBuilder::valueForUnary(shared_ptr<ExpressionUnary> expression) {
+    llvm::Value *value = valueForExpression(expression->getExpression());
+    llvm::Type *type = value->getType();
+
+    // do nothing for plus
+    if (expression->getOperation() == ExpressionUnaryOperation::PLUS)
+        return value;
+
+    if (type == typeU8 || type == typeU32) {
+        return builder->CreateNeg(value);
+    } else if (type == typeS8 || type == typeS32) {
+        return builder->CreateNSWNeg(value);
+    } else if (type == typeR32) {
+        return builder->CreateFNeg(value);
+    }
+
+    markError(0, 0, "Unexpected operation");
+    return nullptr;
+}
+
 llvm::Value *ModuleBuilder::valueForIfElse(shared_ptr<ExpressionIfElse> expression) {
     shared_ptr<Expression> conditionExpression = expression->getCondition();
 
diff --git a/src/Compiler/ModuleBuilder.h b/src/Compiler/ModuleBuilder.h
index b9f0100..872b4ad 100644
--- a/src/Compiler/ModuleBuilder.h
+++ b/src/Compiler/ModuleBuilder.h
@@ -23,6 +23,7 @@ class ExpressionVariable;
 class ExpressionCall;
 class ExpressionIfElse;
 class ExpressionBinary;
+class ExpressionUnary;
 enum class ExpressionBinaryOperation;
 
 class Statement;
@@ -86,6 +87,7 @@ private:
     llvm::Value *valueForBinaryUnsignedInteger(ExpressionBinaryOperation operation, llvm::Value *leftValue, llvm::Value *rightValue);
     llvm::Value *valueForBinarySignedInteger(ExpressionBinaryOperation operation, llvm::Value *leftValue, llvm::Value *rightValue);
     llvm::Value *valueForBinaryReal(ExpressionBinaryOperation operation, llvm::Value *leftValue, llvm::Value *rightValue);
+    llvm::Value *valueForUnary(shared_ptr<ExpressionUnary> expression);
     llvm::Value *valueForIfElse(shared_ptr<ExpressionIfElse> expression);
     llvm::Value *valueForVar(shared_ptr<ExpressionVariable> expression);
     llvm::Value *valueForCall(shared_ptr<ExpressionCall> expression);
diff --git a/src/Lexer/Token.cpp b/src/Lexer/Token.cpp
index 5fcc1df..2adddfe 100644
--- a/src/Lexer/Token.cpp
+++ b/src/Lexer/Token.cpp
@@ -4,21 +4,30 @@ vector<TokenKind> Token::tokensEquality = {
     TokenKind::EQUAL,
     TokenKind::NOT_EQUAL
 };
+
 vector<TokenKind> Token::tokensComparison = {
     TokenKind::LESS,
     TokenKind::LESS_EQUAL,
     TokenKind::GREATER,
     TokenKind::GREATER_EQUAL
 };
+
 vector<TokenKind> Token::tokensTerm = {
     TokenKind::PLUS,
     TokenKind::MINUS
 };
+
 vector<TokenKind> Token::tokensFactor = {
     TokenKind::STAR,
     TokenKind::SLASH,
     TokenKind::PERCENT
 };
+
+vector<TokenKind> Token::tokensUnary = {
+    TokenKind::PLUS,
+    TokenKind::MINUS
+};
+
 vector<TokenKind> Token::tokensBinary = {
     TokenKind::EQUAL,
     TokenKind::NOT_EQUAL,
@@ -35,6 +44,7 @@ vector<TokenKind> Token::tokensBinary = {
     TokenKind::SLASH,
     TokenKind::PERCENT
 };
+
 vector<TokenKind> Token::tokensLiteral = {
     TokenKind::BOOL,
     TokenKind::INTEGER_DEC,
diff --git a/src/Lexer/Token.h b/src/Lexer/Token.h
index c6ee86a..4b1ab57 100644
--- a/src/Lexer/Token.h
+++ b/src/Lexer/Token.h
@@ -65,6 +65,7 @@ public:
     static vector<TokenKind> tokensComparison;
     static vector<TokenKind> tokensTerm;
     static vector<TokenKind> tokensFactor;
+    static vector<TokenKind> tokensUnary;
     static vector<TokenKind> tokensBinary;
     static vector<TokenKind> tokensLiteral;
 
diff --git a/src/Logger.cpp b/src/Logger.cpp
index a2c9543..6cfbd4f 100644
--- a/src/Logger.cpp
+++ b/src/Logger.cpp
@@ -20,6 +20,7 @@
 
 #include "Parser/Expression/Expression.h"
 #include "Parser/Expression/ExpressionBinary.h"
+#include "Parser/Expression/ExpressionUnary.h"
 #include "Parser/Expression/ExpressionIfElse.h"
 #include "Parser/Expression/ExpressionVariable.h"
 #include "Parser/Expression/ExpressionGrouping.h"
@@ -344,7 +345,9 @@ string Logger::toString(shared_ptr<StatementExpression> statement) {
 string Logger::toString(shared_ptr<Expression> expression) {
     switch (expression->getKind()) {
         case ExpressionKind::BINARY:
-            return toString(dynamic_pointer_cast<ExpressionBinary>(expression));
+        return toString(dynamic_pointer_cast<ExpressionBinary>(expression));
+        case ExpressionKind::UNARY:
+            return toString(dynamic_pointer_cast<ExpressionUnary>(expression));
         case ExpressionKind::IF_ELSE:
             return toString(dynamic_pointer_cast<ExpressionIfElse>(expression));
         case ExpressionKind::VAR:
@@ -391,6 +394,17 @@ string Logger::toString(shared_ptr<ExpressionBinary> expression) {
     }
 }
 
+string Logger::toString(shared_ptr<ExpressionUnary> expression) {
+    switch (expression->getOperation()) {
+        case ExpressionUnaryOperation::PLUS:
+            return "+" + toString(expression->getExpression());
+        case ExpressionUnaryOperation::MINUS:
+            return "-" + toString(expression->getExpression());
+        case ExpressionUnaryOperation::INVALID:
+            return "{INVALID}";
+    }
+}
+
 string Logger::toString(shared_ptr<ExpressionIfElse> expression) {
     string text;
 
diff --git a/src/Logger.h b/src/Logger.h
index 3101911..72e6746 100644
--- a/src/Logger.h
+++ b/src/Logger.h
@@ -20,6 +20,7 @@ class StatementExpression;
 
 class Expression;
 class ExpressionBinary;
+class ExpressionUnary;
 class ExpressionIfElse;
 class ExpressionVariable;
 class ExpressionGrouping;
@@ -51,6 +52,7 @@ private:
 
     static string toString(shared_ptr<Expression> expression);
     static string toString(shared_ptr<ExpressionBinary> expression);
+    static string toString(shared_ptr<ExpressionUnary> expression);
     static string toString(shared_ptr<ExpressionIfElse> expression);
     static string toString(shared_ptr<ExpressionVariable> expression);
     static string toString(shared_ptr<ExpressionGrouping> expression);
diff --git a/src/Parser/Expression/ExpressionUnary.cpp b/src/Parser/Expression/ExpressionUnary.cpp
index 420cdd9..ddc570d 100644
--- a/src/Parser/Expression/ExpressionUnary.cpp
+++ b/src/Parser/Expression/ExpressionUnary.cpp
@@ -7,12 +7,15 @@ Expression(ExpressionKind::UNARY, nullptr), expression(expression) {
     switch (token->getKind()) {
         case TokenKind::PLUS:
             operation = ExpressionUnaryOperation::PLUS;
+            valueType = expression->getValueType();
             break;
         case TokenKind::MINUS:
             operation = ExpressionUnaryOperation::MINUS;
+            valueType = expression->getValueType();
             break;
         default:
             operation = ExpressionUnaryOperation::INVALID;
+            valueType = nullptr;
             break;
     }
 }
diff --git a/src/Parser/Parser.cpp b/src/Parser/Parser.cpp
index 9906eeb..cd9b957 100644
--- a/src/Parser/Parser.cpp
+++ b/src/Parser/Parser.cpp
@@ -12,6 +12,7 @@
 #include "Parser/Expression/ExpressionVariable.h"
 #include "Parser/Expression/ExpressionCall.h"
 #include "Parser/Expression/ExpressionIfElse.h"
+#include "Parser/Expression/ExpressionUnary.h"
 #include "Parser/Expression/ExpressionBinary.h"
 #include "Parser/Expression/ExpressionBlock.h"
 
@@ -723,7 +724,7 @@ shared_ptr<Expression> Parser::matchTerm() {
 }
 
 shared_ptr<Expression> Parser::matchFactor() {
-    shared_ptr<Expression> expression = matchPrimary();
+    shared_ptr<Expression> expression = matchUnary();
     if (expression == nullptr)
         return nullptr;
 
@@ -733,6 +734,19 @@ shared_ptr<Expression> Parser::matchFactor() {
     return expression;
 }
 
+shared_ptr<Expression> Parser::matchUnary() {
+    shared_ptr<Token> token = tokens.at(currentIndex);
+
+    if (tryMatchingTokenKinds(Token::tokensUnary, false, true)) {
+        shared_ptr<Expression> expression = matchPrimary();
+        if (expression == nullptr)
+            return nullptr;
+        return make_shared<ExpressionUnary>(token, expression);
+    }
+
+    return matchPrimary();
+}
+
 shared_ptr<Expression> Parser::matchPrimary() {
     shared_ptr<Expression> expression;
     int errorsCount = errors.size();
diff --git a/src/Parser/Parser.h b/src/Parser/Parser.h
index 8e5a8d5..0e27960 100644
--- a/src/Parser/Parser.h
+++ b/src/Parser/Parser.h
@@ -43,7 +43,8 @@ private:
     shared_ptr<Expression> matchComparison(); // <, <=, >, >=
     shared_ptr<Expression> matchTerm(); // +, -
     shared_ptr<Expression> matchFactor(); // *, /, %
-    shared_ptr<Expression> matchPrimary(); // integer, ()
+    shared_ptr<Expression> matchUnary(); // +, -
+    shared_ptr<Expression> matchPrimary(); // literal, ()
 
     shared_ptr<Expression> matchExpressionGrouping();
     shared_ptr<Expression> matchExpressionLiteral();