diff --git a/src/lib.rs b/src/lib.rs
index a4edb0d..a2629b8 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,6 +1,6 @@
 use std::cmp::Ordering;
 
-pub fn partition_by<T, F: FnMut(&T, &T) -> Ordering>
+fn partition_by<T, F: FnMut(&T, &T) -> Ordering>
 (slice: &mut [T], start: isize, end: isize, compare: &mut F) -> isize {
 
     let mut i = start;
@@ -15,7 +15,7 @@ pub fn partition_by<T, F: FnMut(&T, &T) -> Ordering>
 
 }
 
-pub fn quick_sort_by<T, F: FnMut(&T, &T) -> Ordering>
+fn quick_sort_by<T, F: FnMut(&T, &T) -> Ordering>
 (slice: &mut [T], start: isize, end: isize, compare: &mut F) {
 
     if start < end {
@@ -27,7 +27,7 @@ pub fn quick_sort_by<T, F: FnMut(&T, &T) -> Ordering>
 }
 
 pub fn partial_sort_by<T, F: FnMut(&T, &T) -> Ordering>
-(slice: &mut [T], k: isize, compare: &mut F) {
+(slice: &mut [T], k: usize, compare: &mut F) {
 
     let mut start = 0;
     let mut end = slice.len() as isize - 1;
@@ -37,7 +37,7 @@ pub fn partial_sort_by<T, F: FnMut(&T, &T) -> Ordering>
         let index = partition_by(slice, start, end, compare);
         let rank = index + 1;
 
-        if rank >= k {
+        if rank >= k as isize {
             end = index - 1;
         } else if index - start > end - index {
             quick_sort_by(slice, index + 1, end, compare);
@@ -64,11 +64,11 @@ pub fn partial_sort_by<T, F: FnMut(&T, &T) -> Ordering>
 ///
 /// The implementation is based on [this gist](https://gist.github.com/mesuvash/4095565).
 pub fn partial_sort<T: Ord>(slice: &mut [T], k: usize) {
-    partial_sort_by(slice, k as isize, &mut |x, y| x.cmp(y));
+    partial_sort_by(slice, k, &mut |x, y| x.cmp(y));
 }
 
 pub fn partial_sort_by_key<T, O: Ord, F: FnMut(&T) -> O>(slice: &mut [T], k: usize, key: &mut F) {
-    partial_sort_by(slice, k as isize, &mut |x, y| key(x).cmp(&key(y)));
+    partial_sort_by(slice, k, &mut |x, y| key(x).cmp(&key(y)));
 }
 
 #[cfg(test)]