diff --git a/smnp/ast/parser.py b/smnp/ast/parser.py
index d54b1e8..5af9786 100644
--- a/smnp/ast/parser.py
+++ b/smnp/ast/parser.py
@@ -93,22 +93,50 @@ class Parser:
 
     # leftAssociative -> left | left OP right
     @staticmethod
-    def leftAssociativeOperatorParser(leftParser, operatorTokenType, rightParser, createNode):
+    def leftAssociativeOperatorParser(leftParser, operatorTokenTypes, rightParser, createNode):
         from smnp.ast.node.operator import OperatorNode
+
         def parse(input):
+            operatorParser = Parser.oneOfTerminals(*operatorTokenTypes, createNode=lambda val, pos: OperatorNode.withChildren([val], pos))
             left = leftParser(input)
             if left.result:
-                operator = Parser.terminalParser(operatorTokenType, lambda val, pos: OperatorNode.withChildren([val], pos))(input)
+                operator = operatorParser(input)
                 while operator.result:
                     right = rightParser(input)
                     left = ParseResult.OK(createNode(left.node, operator.node, right.node))
-                    operator = Parser.terminalParser(operatorTokenType, lambda val, pos: OperatorNode.withChildren([val], pos))(input)
+                    operator = operatorParser(input)
                 return left
 
             return ParseResult.FAIL()
 
         return parse
 
+    @staticmethod
+    def oneOfTerminals(*tokenTypes, createNode=None):
+        return Parser.oneOf(*[ Parser.terminalParser(expectedType, createNode=createNode) for expectedType in tokenTypes ])
+
+    # leftAssociative -> left OP right | right
+    @staticmethod
+    def leftAssociativeOperatorOrRightParser(leftParser, operatorTokenType, rightParser, createNode):
+        from smnp.ast.node.operator import OperatorNode
+        def parse(input):
+            left = leftParser(input)
+            oneAtLeast = False
+            if left.result:
+                operator = Parser.terminalParser(operatorTokenType, lambda val, pos: OperatorNode.withChildren([val], pos))(input)
+                while operator.result:
+                    oneAtLeast = True
+                    right = rightParser(input)
+                    left = ParseResult.OK(createNode(left.node, operator.node, right.node))
+                    operator = Parser.terminalParser(operatorTokenType, lambda val, pos: OperatorNode.withChildren([val], pos))(input)
+
+                if oneAtLeast:
+                    return left
+
+            return ParseResult.FAIL()
+
+        return Parser.oneOf(parse, rightParser)
+
     # loop -> start item* end
     @staticmethod
     def loop(startParser, itemParser, endParser, createNode):
@@ -154,6 +182,10 @@ class Parser:
 
         return parse
 
+    @staticmethod
+    def epsilon():
+        return lambda *args: ParseResult.OK(NoneNode())
+
     @staticmethod
     def many(parser, createNode):
         def parse(input):
diff --git a/smnp/calc.py b/smnp/calc.py
new file mode 100644
index 0000000..2bd9a85
--- /dev/null
+++ b/smnp/calc.py
@@ -0,0 +1,66 @@
+from smnp.ast.node.model import Node
+from smnp.ast.parser import Parser
+from smnp.token.tokenizer import tokenize
+from smnp.token.type import TokenType
+
+
+class Atom(Node):
+    def __init__(self, value, pos):
+        super().__init__(pos)
+        self.children = [value]
+
+    @property
+    def value(self):
+        return self[0]
+
+class Operation(Node):
+    def __init__(self, left, op, right, pos):
+        super().__init__(pos)
+        self.children = [left, op, right]
+
+    @property
+    def left(self):
+        return self[0]
+
+    @property
+    def operator(self):
+        return self[1]
+
+    @property
+    def right(self):
+        return self[2]
+
+def atom(input):
+    return Parser.terminalParser(TokenType.INTEGER, lambda val, pos: Atom(val, pos))(input)
+
+def chain(input):
+    return Parser.leftAssociativeOperatorParser(atom, [TokenType.DOT], atom, lambda left, op, right: Operation(left, op, right, op.pos))(input)
+
+def factor(input):
+    return Parser.leftAssociativeOperatorParser(chain, [TokenType.DOUBLE_ASTERISK], chain, lambda left, op, right: Operation(left, op, right, op.pos))(input)
+
+def term(input):
+    return Parser.leftAssociativeOperatorParser(factor, [TokenType.ASTERISK, TokenType.SLASH], factor, lambda left, op, right: Operation(left, op, right, op.pos))(input)
+
+def expr(input):
+    return Parser.leftAssociativeOperatorParser(term, [TokenType.PLUS, TokenType.MINUS], term, lambda left, op, right: Operation(left, op, right, op.pos))(input)
+
+def evaluate(node):
+    if type(node) == Atom:
+        return node.value
+    lhs = evaluate(node.left)
+    rhs = evaluate(node.right)
+    return {
+        "+": int(lhs) + int(rhs),
+        "*": int(lhs) * int(rhs),
+        "-": int(lhs) - int(rhs),
+        "/": int(lhs) / int(rhs),
+        "**": int(lhs) ** int(rhs)
+    }[node.operator.value]
+
+def draft():
+
+    tokens = tokenize(['2 + 2 * 2 / 2'])
+    node = expr(tokens).node
+    node.print()
+    print(evaluate(node))
diff --git a/smnp/main.py b/smnp/main.py
index 214e397..da14e33 100644
--- a/smnp/main.py
+++ b/smnp/main.py
@@ -1,14 +1,12 @@
-import sys
-
+from smnp.calc import draft
 from smnp.error.base import SmnpException
-from smnp.library.loader import loadStandardLibrary
-from smnp.program.interpreter import Interpreter
 
 
 def main():
     try:
-        stdLibraryEnv = loadStandardLibrary()
-        Interpreter.interpretFile(sys.argv[1], printTokens=False, printAst=True, execute=False, baseEnvironment=stdLibraryEnv)
+        #stdLibraryEnv = loadStandardLibrary()
+        #Interpreter.interpretFile(sys.argv[1], printTokens=False, printAst=True, execute=False, baseEnvironment=stdLibraryEnv)
+        draft()
 
     except SmnpException as e:
         print(e.message())
diff --git a/smnp/token/tokenizer.py b/smnp/token/tokenizer.py
index aa8a1af..07de7f5 100644
--- a/smnp/token/tokenizer.py
+++ b/smnp/token/tokenizer.py
@@ -20,11 +20,14 @@ tokenizers = (
     defaultTokenizer(TokenType.CLOSE_SQUARE),
     defaultTokenizer(TokenType.OPEN_ANGLE),
     defaultTokenizer(TokenType.CLOSE_ANGLE),
+    defaultTokenizer(TokenType.DOUBLE_ASTERISK),
     defaultTokenizer(TokenType.ASTERISK),
     defaultTokenizer(TokenType.ASSIGN),
     defaultTokenizer(TokenType.ARROW),
     defaultTokenizer(TokenType.COMMA),
+    defaultTokenizer(TokenType.SLASH),
     defaultTokenizer(TokenType.MINUS),
+    defaultTokenizer(TokenType.PLUS),
     defaultTokenizer(TokenType.DOTS),
     defaultTokenizer(TokenType.AMP),
     defaultTokenizer(TokenType.DOT),
diff --git a/smnp/token/type.py b/smnp/token/type.py
index 2489903..e3ab14d 100644
--- a/smnp/token/type.py
+++ b/smnp/token/type.py
@@ -2,6 +2,7 @@ from enum import Enum
 
 
 class TokenType(Enum):
+    DOUBLE_ASTERISK = '**'
     OPEN_CURLY = '{'
     CLOSE_CURLY = '}'
     OPEN_PAREN = '('
@@ -14,7 +15,9 @@ class TokenType(Enum):
     ASSIGN = '='
     ARROW = '->'
     COMMA = ','
+    SLASH = '/'
     MINUS = '-'
+    PLUS = '+'
     DOTS = '...'
     AMP = '&'
     DOT = '.'