diff --git a/src/bam/flags.rs b/src/bam/flags.rs
index ed2d8d8fc..bacd01b09 100644
--- a/src/bam/flags.rs
+++ b/src/bam/flags.rs
@@ -1,15 +1,14 @@
 //! A module that provides an easier way to work with SAM flags.
 //! It achieves this by providing a struct (`Flag`) with associated constants representing
-//! flags, and the `check_flag()` function that allows testing if specific flags are set or not set.
+//! flags. And the `is_in_flag()` and `is_not_in_flag()` functions that allow testing if specific flags are set or not set.
 //!
-//! For example, the following code tests if the read flag has the FIRST_IN_PAIR flag set and the MATE_UNMAPPED flag not set:
 //! ```
-//! use rust_htslib::bam::flags{Flag, check_flag};
+//! use rust_htslib::bam::flags{Flag, is_in_flag, is_not_in_flag};
 //! let read_flag = record.flag(); // in general this is the way to obtain a flag.
 //! let read_flag = 64;
-//! assert_eq!(check_flag(read_flag, Flag::FIRST_IN_PAIR, Flag::MATE_UNMAPPED), true);
+//! assert_eq!(is_in_flag(read_flag, Flag::FIRST_IN_PAIR), true);
+//! assert_eq!(is_not_in_flag(read_flag, Flag::MATE_UNMAPPED), true);
 //! ```
-
 ///
 /// This structure contains constants representing SAM flag values as u16.
 /// Using this structure incurs no runtime cost.
@@ -37,6 +36,54 @@ impl Flag {
     pub const SUPPLEMENTARY: u16 = 2048;
 }
 
+pub fn is_not_in_flag(flag: u16, not_in: u16) -> bool {
+    //! This function uses bitwise operations to test if flags are not set
+    //! # Arguments
+    //! * `flag`: u16 - The record flag you want to test
+    //! * `not_in`: u16 - The flags you want to check if they are not set (use 0 for no test)
+    //!
+    //! # Usage:
+    //! example: let test if a flag is primary alignment and did not fail QC
+    //! ```
+    //! use rust_htslib::bam::flags;
+    //! use rust_htslib::bam::flags::Flag;
+    //! let read_flag = 65;
+    //! assert_eq!(flags::is_not_in_flag(read_flag, Flag::NOT_PRIMARY_ALN + Flag::FAIL_QC), true);
+    //! ```
+    //! let test that the read is mapped.
+    //! ```
+    //!
+    //! use rust_htslib::bam::flags::{Flag, is_not_in_flag};
+    //! let read_flag = 18;
+    //! assert_eq!(is_not_in_flag(read_flag, Flag::READ_UNMAPPED), true);
+    //! ```
+    //!
+    if (not_in & flag) != 0 {
+        return false;
+    }
+    true
+}
+pub fn is_in_flag(flag: u16, in_: u16) -> bool {
+    //! This function uses bitwise operations to test if flags are set
+    //! # Arguments
+    //! * `flag`: u16 - The record flag you want to test
+    //! * `in_`: u16 - The flags you want to check if they are set (use 0 for no test)
+    //!
+    //! # Usage:
+    //! example: let test if a flag is both paired and first in pair
+    //! ```
+    //! use rust_htslib::bam::flags::{Flag, is_in_flag};
+    //! let read_flag = 65;
+    //! assert_eq!(is_in_flag(read_flag, Flag::PAIRED + Flag::FIRST_IN_PAIR), true);
+    //! ```
+
+    if (in_ & flag) != in_ {
+        return false;
+    }
+    true
+}
+
+/* Deprecated
 pub fn check_flag(flag: u16, in_: u16, not_in: u16) -> bool {
     //! This function uses bitwise operations to test if flags are set or not.
     //!
@@ -79,3 +126,4 @@ pub fn check_flag(flag: u16, in_: u16, not_in: u16) -> bool {
     }
     return true;
 }
+*/