Rewrote grammar, implemented two visitors

src/main/antlr4/de/hsrm/compiler/Klang/Klang.g4

@@ -1,25 +1,44 @@
 grammar Klang;
 
 parse
-  : multiplicativeExpr <EOF>
+  : block <EOF>
   ;
 
-multiplicativeExpr
-  : unaryExpression (MULT unaryExpression)*  
+block
+  : statement*
   ;
 
-unaryExpression
-  : INTEGER_LITERAL
+statement
+  : print
   ;
 
+print
+  : PRINT expression SCOL
+  ;
+
+expression
+  : atom MULT atom #multiplicationExpression
+  | atom op=(ADD | SUB) atom #additiveExpression
+  | atom MOD atom #moduloExpression
+  | SUB atom #unaryNegateExpression
+  ;
+
+atom
+  : INTEGER_LITERAL #intAtom
+  ;
+
+PRINT: 'print';
+SCOL: ';';
+
+MULT: '*';
+ADD: '+';
+SUB: '-';
+MOD: '%';
+
 INTEGER_LITERAL
   : [0-9]+
   ;
 
-MULT
-  : '*'
-  ;
-
 WS
  : [ \t\r\n] -> skip
  ;