diff --git a/src/collection/__comm__/_str_hash.scad b/src/collection/__comm__/_str_hash.scad
new file mode 100644
index 00000000..ab9fc52b
--- /dev/null
+++ b/src/collection/__comm__/_str_hash.scad
@@ -0,0 +1,11 @@
+use <../../util/sum.scad>;
+
+function _str_hash(value) = 
+    let(
+	    s = str(value),
+		leng = len(s)
+	)
+	sum([
+	    for(i = [0:leng - 1])
+		ord(s[i]) * pow(31, leng - 1 - i)
+	]);
\ No newline at end of file
diff --git a/src/collection/_impl/_hashset_impl.scad b/src/collection/_impl/_hashset_impl.scad
new file mode 100644
index 00000000..627f804a
--- /dev/null
+++ b/src/collection/_impl/_hashset_impl.scad
@@ -0,0 +1,23 @@
+use <../../util/slice.scad>;
+use <../../util/some.scad>;
+
+function _hashset_add(set, elem, hash, eq) =
+    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)
+	);
+
+function _hashset(elems, leng, buckets, hash, eq, i = 0) = 
+    i == leng ? buckets :
+	_hashset(elems, leng, _hashset_add(buckets, elems[i], hash, eq), hash, eq, 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
diff --git a/src/collection/hashset.scad b/src/collection/hashset.scad
index 16657040..04643ff8 100644
--- a/src/collection/hashset.scad
+++ b/src/collection/hashset.scad
@@ -1,21 +1,28 @@
-use <../util/sum.scad>;
+use <__comm__/_str_hash.scad>;
+use <_impl/_hashset_impl.scad>;
 use <../util/slice.scad>;
 use <../util/some.scad>;
 
-function strhash(value) = 
-    let(
-	    s = str(value),
-		leng = len(s)
-	)
-	sum([
-	    for(i = [0:leng - 1])
-		ord(s[i]) * pow(31, leng - 1 - i)
-	]);
-	
-df_hash = function(e) strhash(e);
+// public functions: hashset, hashset_has, hashset_add, hashset_del, hashset_list
+
+/*
+use <collection/hashset.scad>;
+
+s = hashset([1, 2, 3, 4, 5, 2, 3, 5]);
+echo(hashset_list(s));
+s2 = hashset_add(s, 9);
+echo(hashset_list(s2));
+
+echo(hashset_has(s2, 13));
+
+echo(hashset_list(hashset_del(s2, 2)));
+*/
+
+
+df_hash = function(e) _str_hash(e);
 df_eq = function(e1, e2) e1 == e2;
 	
-function hashset(elems, bucket_size = 16, hash = df_hash, eq = df_eq) =
+function hashset(elems, hash = df_hash, eq = df_eq, bucket_size = 16) =
     let(
 	    elems_undef = is_undef(elems),
 	    size = elems_undef ? bucket_size : len(elems),
@@ -23,26 +30,12 @@ function hashset(elems, bucket_size = 16, hash = df_hash, eq = df_eq) =
 	)
 	elems_undef ? buckets :
 	_hashset(elems, len(elems), buckets, hash, eq);
-	
-function _hashset(elems, leng, buckets, hash, eq, i = 0) = 
-    i == leng ? buckets :
-	_hashset(elems, leng, hashset_add(buckets, elems[i], hash, eq), hash, eq, i + 1);
 
 function hashset_has(set, elem, hash = df_hash, eq = df_eq) =
     some(set[hash(elem) % len(set)], function(e) eq(e, elem));
 	
 function hashset_add(set, elem, hash = df_hash, eq = df_eq) =
-    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)
-	);
+    _hashset_add(set, elem, hash, eq);
 	
 function hashset_del(set, elem, hash = df_hash, eq = df_eq) =
     let(
@@ -59,10 +52,6 @@ function hashset_del(set, elem, hash = df_hash, eq = df_eq) =
 		slice(set, bidx + 1)
 	);
 
-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_list(set) = [
     for(bucket = set) 
         for(elem = bucket)