diff --git a/src/collection/_impl/_hashset_add_impl.scad b/src/collection/_impl/_hashset_add_impl.scad
new file mode 100644
index 00000000..0cfa822d
--- /dev/null
+++ b/src/collection/_impl/_hashset_add_impl.scad
@@ -0,0 +1,15 @@
+use <../../util/slice.scad>;
+use <../../util/some.scad>;
+
+function _hashset_add(set, elem, eq, hash) =
+    let(
+	    idx = hash(elem) % len(set),
+		bucket = set[idx]
+	)
+	len(bucket) == 0 ? concat(slice(set, 0, idx), [[elem]], slice(set, idx + 1)) :
+	some(bucket, function(e) eq(e, elem)) ? set :
+	concat(
+	    slice(set, 0, idx), 
+		[concat(bucket, [elem])], 
+		slice(set, idx + 1)
+	);
\ No newline at end of file
diff --git a/src/collection/_impl/_hashset_impl.scad b/src/collection/_impl/_hashset_impl.scad
index 0e8c6d04..625b70bd 100644
--- a/src/collection/_impl/_hashset_impl.scad
+++ b/src/collection/_impl/_hashset_impl.scad
@@ -1,23 +1,5 @@
-use <../../util/slice.scad>;
-use <../../util/some.scad>;
-
-function _hashset_add(set, elem, eq, hash) =
-    let(
-	    idx = hash(elem) % len(set),
-		bucket = set[idx]
-	)
-	len(bucket) == 0 ? concat(slice(set, 0, idx), [[elem]], slice(set, idx + 1)) :
-	some(bucket, function(e) eq(e, elem)) ? set :
-	concat(
-	    slice(set, 0, idx), 
-		[concat(bucket, [elem])], 
-		slice(set, idx + 1)
-	);
+use <_hashset_add_impl.scad>;
 
 function _hashset(elems, leng, buckets, eq, hash, i = 0) = 
     i == leng ? buckets :
-	_hashset(elems, leng, _hashset_add(buckets, elems[i], eq, hash), eq, hash, i + 1);
-
-function _find(lt, elem, eq, leng, i = 0) =
-    i == leng ? -1 :
-    eq(lt[i], elem) ? i : _find(lt, elem, eq, leng, i + 1);
\ No newline at end of file
+	_hashset(elems, leng, _hashset_add(buckets, elems[i], eq, hash), eq, hash, i + 1);
\ No newline at end of file
diff --git a/src/collection/hashset.scad b/src/collection/hashset.scad
index f4a4ccc5..47c08575 100644
--- a/src/collection/hashset.scad
+++ b/src/collection/hashset.scad
@@ -1,14 +1,8 @@
 use <__comm__/_str_hash.scad>;
 use <_impl/_hashset_impl.scad>;
-use <../util/slice.scad>;
-use <../util/some.scad>;
-
-// public functions: hashset, hashset_has, hashset_add, hashset_del, hashset_list
-
-df_hash = function(e) _str_hash(e);
-df_eq = function(e1, e2) e1 == e2;
+use <_impl/_hashset_add_impl.scad>;
 	
-function hashset(lt, eq = df_eq, hash = df_hash, bucket_numbers) =
+function hashset(lt, eq = function(e1, e2) e1 == e2, hash = function(e) _str_hash(e), bucket_numbers) =
     let(
 	    lt_undef = is_undef(lt),
 		bucket_numbers_undef = is_undef(bucket_numbers),
@@ -16,25 +10,4 @@ function hashset(lt, eq = df_eq, hash = df_hash, bucket_numbers) =
 		               (lt_undef ? 16 : len(lt)) : bucket_numbers,
 	    buckets = [for(i = [0:b_numbers - 1]) []]
 	)
-	lt_undef ? buckets : _hashset(lt, len(lt), buckets, eq, hash);
-
-function hashset_has(set, elem, eq = df_eq, hash = df_hash) =
-    some(set[hash(elem) % len(set)], function(e) eq(e, elem));
-	
-function hashset_add(set, elem, eq = df_eq, hash = df_hash) =
-    _hashset_add(set, elem, eq, hash);
-	
-function hashset_del(set, elem, eq = df_eq, hash = df_hash) =
-    let(
-	    bidx = hash(elem) % len(set),
-		bucket = set[bidx],
-		leng = len(bucket)
-	)
-	leng == 0 ? set :
-	let(i = _find(bucket, elem, eq, leng))
-	i == -1 ? set : 
-	concat(
-	    slice(set, 0, bidx), 
-		[concat(slice(bucket, 0, i), slice(bucket, i + 1))],
-		slice(set, bidx + 1)
-	);
\ No newline at end of file
+	lt_undef ? buckets : _hashset(lt, len(lt), buckets, eq, hash);
\ No newline at end of file
diff --git a/src/collection/hashset_add.scad b/src/collection/hashset_add.scad
new file mode 100644
index 00000000..8897b8ae
--- /dev/null
+++ b/src/collection/hashset_add.scad
@@ -0,0 +1,5 @@
+use <__comm__/_str_hash.scad>;
+use <_impl/_hashset_add_impl.scad>;
+
+function hashset_add(set, elem, eq = function(e1, e2) e1 == e2, hash = function(e) _str_hash(e)) =
+    _hashset_add(set, elem, eq, hash);
\ No newline at end of file
diff --git a/src/collection/hashset_del.scad b/src/collection/hashset_del.scad
new file mode 100644
index 00000000..0ee22c8c
--- /dev/null
+++ b/src/collection/hashset_del.scad
@@ -0,0 +1,21 @@
+use <__comm__/_str_hash.scad>;
+use <../util/slice.scad>;
+
+function _find(lt, elem, eq, leng, i = 0) =
+    i == leng ? -1 :
+    eq(lt[i], elem) ? i : _find(lt, elem, eq, leng, i + 1);
+
+function hashset_del(set, elem, eq = function(e1, e2) e1 == e2, hash = function(e) _str_hash(e)) =
+    let(
+	    bidx = hash(elem) % len(set),
+		bucket = set[bidx],
+		leng = len(bucket)
+	)
+	leng == 0 ? set :
+	let(i = _find(bucket, elem, eq, leng))
+	i == -1 ? set : 
+	concat(
+	    slice(set, 0, bidx), 
+		[concat(slice(bucket, 0, i), slice(bucket, i + 1))],
+		slice(set, bidx + 1)
+	);
\ No newline at end of file
diff --git a/src/collection/hashset_has.scad b/src/collection/hashset_has.scad
new file mode 100644
index 00000000..13b0bc16
--- /dev/null
+++ b/src/collection/hashset_has.scad
@@ -0,0 +1,5 @@
+use <__comm__/_str_hash.scad>;
+use <../util/some.scad>;
+
+function hashset_has(set, elem, eq = function(e1, e2) e1 == e2, hash = function(e) _str_hash(e)) =
+    some(set[hash(elem) % len(set)], function(e) eq(e, elem));
\ No newline at end of file
diff --git a/test/collection/test_hashset.scad b/test/collection/test_hashset.scad
index d0fd5b1e..0bc076b1 100644
--- a/test/collection/test_hashset.scad
+++ b/test/collection/test_hashset.scad
@@ -1,6 +1,9 @@
 use <unittest.scad>;
 use <collection/hashset.scad>;
 use <collection/hashset_list.scad>;
+use <collection/hashset_add.scad>;
+use <collection/hashset_del.scad>;
+use <collection/hashset_has.scad>;
 
 module test_hashset() {
     echo("==== test_hashset ====");