Implemented addition

src/build/Function.go

@@ -113,6 +113,16 @@ func (f *Function) CompileInstruction(line token.List) error {
 		return f.CompileFunctionCall(expr)
 	}
 
+	if expr.Token.Kind == token.Operator {
+		switch expr.Token.Text() {
+		case "+=":
+			name := expr.Children[0].Token.Text()
+			number, _ := strconv.Atoi(expr.Children[1].Token.Text())
+			f.Assembler.AddRegisterNumber(f.Variables[name].Register, uint64(number))
+			return nil
+		}
+	}
+
 	return errors.New(&errors.InvalidInstruction{Instruction: expr.Token.Text()}, f.File, expr.Token.Position)
 }