diff --git a/srfi/143.sld b/srfi/143.sld
index eb084a00..59a09ac5 100644
--- a/srfi/143.sld
+++ b/srfi/143.sld
@@ -28,9 +28,10 @@
     fxarithmetic-shift 
     fxarithmetic-shift-left fxarithmetic-shift-right
 ;  fxbit-count fxlength 
-    fxif fxbit-set? ;fxcopy-bit
-;  fxfirst-set-bit fxbit-field
-;  fxbit-field-rotate fxbit-field-reverse
+    fxif fxbit-set? fxcopy-bit
+    ;fxfirst-set-bit 
+    fxbit-field
+    fxbit-field-rotate fxbit-field-reverse
   )
   (inline
     fx-width
@@ -46,7 +47,10 @@
     fxnot fxand fxior fxxor 
     fxarithmetic-shift 
     fxarithmetic-shift-left fxarithmetic-shift-right
-    fxif fxbit-set?
+    fxif fxbit-set? fxcopy-bit
+    ;fxfirst-set-bit 
+    fxbit-field
+    mask
   )
   (begin
     (define (fx-width) 31)
@@ -140,5 +144,42 @@
          Cyc_check_fixnum(data, i);
          int result = ((obj_obj2int(i)) & (1 << (obj_obj2int(index))));
          return_closcall1(data, k, result ? boolean_t : boolean_f); ")
+
+    (define (fxcopy-bit index to bool)
+      (if bool
+          (fxior to (fxarithmetic-shift-left 1 index))
+          (fxand to (fxnot (fxarithmetic-shift-left 1 index)))))
+
+    ;; Helper function
+    (define (mask start end) (fxnot (fxarithmetic-shift-left -1 (- end start))))
+
+    ;(define (fxfirst-set-bit i) (- (fxbit-count (fxxor i (- i 1))) 1))
+    
+    (define (fxbit-field n start end)
+      (fxand (mask start end) (fxarithmetic-shift n (- start))))
+
+    (define (fxbit-field-rotate n count start end)
+      (define width (fx- end start))
+      (set! count (modulo count width))
+      (let ((mask (fxnot (fxarithmetic-shift -1 width))))
+        (define zn (fxand mask (fxarithmetic-shift n (- start))))
+        (fxior (fxarithmetic-shift
+                 (fxior (fxand mask (fxarithmetic-shift zn count))
+                         (fxarithmetic-shift zn (- count width)))
+                 start)
+                (fxand (fxnot (fxarithmetic-shift mask start)) n))))
+    
+    (define (fxreverse k n)
+      (do ((m (if (negative? n) (fxnot n) n) (fxarithmetic-shift-right m 1))
+           (k (fx+ -1 k) (fx+ -1 k))
+           (rvs 0 (fxior (fxarithmetic-shift-left rvs 1) (fxand 1 m))))
+          ((fxnegative? k) (if (fxnegative? n) (fxnot rvs) rvs))))
+    
+    (define (fxbit-field-reverse n start end)
+      (define width (- end start))
+      (let ((mask (fxnot (fxarithmetic-shift-left -1 width))))
+        (define zn (fxand mask (fxarithmetic-shift-right n start)))
+        (fxior (fxarithmetic-shift-left (fxreverse width zn) start)
+                (fxand (fxnot (fxarithmetic-shift-left mask start)) n))))
   ))