diff --git a/source/Ox.js b/source/Ox.js
index 9d000683..12102fb3 100644
--- a/source/Ox.js
+++ b/source/Ox.js
@@ -365,10 +365,10 @@ Ox.every <f> Tests if every element of a collection satisfies a given condition
     > Ox.every([true, true, true])
     true
 @*/
-Ox.every = function(obj, fn) {
-    return Ox.filter(Ox.values(obj), fn || function(v) {
+Ox.every = function(col, fn) {
+    return Ox.filter(Ox.values(col), fn || function(v) {
         return v;
-    }).length == Ox.len(obj);
+    }).length == Ox.len(col);
 };
 
 /*@
@@ -383,10 +383,10 @@ Ox.filter <f> Filters a collection by a given condition
     'foobar'
 @*/
 
-Ox.filter = function(obj, fn) {
-    var type = Ox.typeOf(obj),
+Ox.filter = function(col, fn) {
+    var type = Ox.typeOf(col),
         ret = type == 'array' ? [] : type == 'object' ? {} : '';
-    Ox.forEach(obj, function(v, k) {
+    Ox.forEach(col, function(v, k) {
         if (fn(v, k)) {
             if (type == 'array') {
                 ret.push(v);
@@ -886,6 +886,34 @@ Ox.some = function(obj, fn) {
     return Ox.filter(Ox.values(obj), fn).length > 0;
 };
 
+/*@
+Ox.substr <f> Returns a substring or sub-array
+    Ox.sub behaves like collection[start:stop] in Python
+    (or, for strings, like str.substring() with negative values for stop)
+    > Ox.sub([1, 2, 3], 1, -1)
+    [2]
+    > Ox.sub('foobar', 1)
+    "oobar"
+    > Ox.sub('foobar', -1)
+    "r"
+    > Ox.sub('foobar', 1, 5)
+    "ooba"
+    > Ox.sub('foobar', 1, -1)
+    "ooba"
+    > Ox.sub('foobar', -5, 5)
+    "ooba"
+    > Ox.sub('foobar', -5, -1)
+    "ooba"
+@*/
+Ox.sub = function(col, start, stop) {
+    stop = Ox.isUndefined(stop) ? col.length : stop;
+    start = start < 0 ? col.length + start : start;
+    stop = stop < 0 ? col.length + stop : stop;
+    return Ox.isArray(col) ? Ox.filter(col, function(val, key) {
+        return key >= start && key < stop;
+    }) : col.substring(start, stop);
+}
+
 /*@
 Ox.sum <f> Returns the sum of the values of a collection
     > Ox.sum(1, 2, 3)
@@ -4255,13 +4283,11 @@ Ox.substr <f> A better <code>substr</code>
     > Ox.substr('foobar', -5, -1)
     "ooba"
 @*/
-// fixme: this would be nice to have for arrays, too
+// deprecated, use Ox.sub()
 Ox.substr = function(str, start, stop) {
     // fixme: needed?
     stop = Ox.isUndefined(stop) ? str.length : stop;
     return str.substring(
-        start < 0 ? str.length + start : start,
-        stop < 0 ? str.length + stop : stop
     );
 };