From c66b22bb2c3934786dd986f81ec20ad7f5801df5 Mon Sep 17 00:00:00 2001
From: Justin Lin <justin.sdk@gmail.com>
Date: Thu, 4 Mar 2021 17:14:39 +0800
Subject: [PATCH] add hashset

---
 src/collection/hashset.scad | 72 +++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 src/collection/hashset.scad

diff --git a/src/collection/hashset.scad b/src/collection/hashset.scad
new file mode 100644
index 00000000..b88d5774
--- /dev/null
+++ b/src/collection/hashset.scad
@@ -0,0 +1,72 @@
+use <../util/sum.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);
+df_eq = function(e1, e2) e1 == e2;
+	
+function hashset(elems, bucket_size = 16, hash = df_hash, eq = df_eq) =
+    let(
+	    elems_undef = is_undef(elems),
+	    size = elems_undef ? bucket_size : len(elems),
+	    buckets = [for(i = [0:bucket_size - 1]) []]
+	)
+	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)
+	);
+	
+function hashset_del(set, elem, hash = df_hash, eq = df_eq) =
+    let(
+	    bidx = hash(elem) % len(set),
+		bucket = set[bidx],
+		leng = len(bucket)
+	)
+	leng == 0 ? set :
+	let(i = _find(bucket, elem, eq, leng), _ = echo(i))
+	i == -1 ? set : 
+	concat(
+	    slice(set, 0, bidx), 
+		[concat(slice(bucket, 0, i), slice(bucket, i + 1))],
+		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)
+            elem		
+];
\ No newline at end of file