diff --git a/lib/array-ext.js b/lib/array-ext.js
index 27470a5..e5f6980 100644
--- a/lib/array-ext.js
+++ b/lib/array-ext.js
@@ -1,98 +1,99 @@
+// batteries
+// Copyright 2010 - 2011 Sami Samhuri <sami@samhuri.net>
+
+var ArrayExt =
+{ at: at
+, compact: compact
+, first: first
+, flatten: flatten
+, grep: grep
+, last: last
+, max: max
+, min: min
+, pluck: pluck
+, sortBy: sortBy
+, unique: unique
+};
+
 exports.extendNative = function() {
-    Object.keys(ArrayExt).forEach(function(k) {
-        if (Array.prototype[k]) return; // don't overwrite existing members
-        Array.prototype[k] = function() {
-            var fn = ArrayExt[k]
-              , args = [].slice.call(arguments)
-              ;
-            args.unshift(this);
-            return fn.apply(ArrayExt, args);
-        };
-    });
+  require('./ext').extend(Array, ArrayExt);
 };
 
-var ArrayToString = [].toString();
+require('./object-ext').extend(exports, ArrayExt);
 
-var ArrayExt = exports.ArrayExt = {
-    
-// abbrev
+// TODO
+// - abbrev
+// - pack
+// - partition
 
-    // [1,2,3,4,5].at(-1) => 5
-    at: function(a, i) {
-        if (i >= 0) return a[i];
-        return a[a.length + i];
-    }
+// [1,2,3,4,5].at(-1) => 5
+function at(a, i) {
+  if (i >= 0) return a[i];
+  return a[a.length + i];
+}
 
-    // TODO make this work for non-array objects
-  , compact: function(a) {
-        var b = []
-          , i = a.length
-          ;
-        while (i--) {
-            if (a[i] !== null && a[i] !== undefined) b[i] = a[i];
-        }
-        return b;
-    }
+// TODO make this work for non-array objects
+function compact(a) {
+  var b = []
+    , i = a.length
+    ;
+  while (i--) {
+    if (a[i] !== null && a[i] !== undefined) b[i] = a[i];
+  }
+  return b;
+}
 
-  , first: function(a) { return a[0]; }
-  
-    // Based on underscore.js's flatten
-  , flatten: function(a) {
-        return a.reduce(function(initial, elem) {
-            if (elem && elem.flatten) initial = initial.concat(elem.flatten());
-            else initial.push(elem);
-            return initial;
-        });
-    }
+function first(a) { return a[0]; }
 
-  , grep: function(a, regex) {
-        return a.filter(function(v) { return regex.test(v); });
-    }
+// Based on underscore.js's flatten
+function flatten(a) {
+  return a.reduce(function(initial, elem) {
+    if (elem && elem.flatten) initial = initial.concat(elem.flatten());
+    else initial.push(elem);
+    return initial;
+  });
+}
 
-  , last: function(a) { return a[a.length-1]; }
+function grep(a, regex) {
+  return a.filter(function(v) { return regex.test(v); });
+}
 
-  , max: function(a) {
-        return a.reduce(function(max, v) { return v > max ? v : max });
-    }
+function last(a) { return a[a.length-1]; }
 
-  , min: function(a) {
-        return a.reduce(function(min, v) { return v < min ? v : min });
-    }
+function max(a) {
+  return a.reduce(function(max, v) { return v > max ? v : max });
+}
 
-    // pack
-    // partition
+function min(a) {
+  return a.reduce(function(min, v) { return v < min ? v : min });
+}
 
-  , pluck: function(a /* , key paths, ... */) {
-        var args = [].slice.call(arguments, 1);
-        args.unshift(a);
-        return pluck.apply(null, args);
-    }
+function pluck(a /* , key paths, ... */) {
+  var args = [].slice.call(arguments, 1);
+  args.unshift(a);
+  return pluck.apply(null, args);
+}
 
-  , sortBy: function(arr, keyPath) {
-        return arr.slice().sort(function(a, b) {
-            var propA = drillInto(a)
-              , propB = drillInto(b);
-            if (propA < propB) return -1
-            if (propA > propB) return 1
-            return 0
-        });
-    }
+function sortBy(arr, keyPath) {
+  return arr.slice().sort(function(a, b) {
+    var propA = drillInto(a)
+      , propB = drillInto(b);
+    if (propA < propB) return -1
+    if (propA > propB) return 1
+    return 0
+  });
+}
 
-  , toString: function(a) {
-        return '[' + ArrayToString.call(a) + ']';
-    }
-
-  , unique: function(a) {
-        var b = []
-          , i = 0
-          , n = a.length
-          ;
-        for (; i < n; ++i) {
-            if (b.indexOf(a[i]) === -1) b.push(a[i]);
-        }
-        return b;
-    }
-};
+function unique(a) {
+  var b = []
+    , i = 0
+    , n = a.length
+    ;
+  for (; i < n; ++i) {
+    if (b.indexOf(a[i]) === -1) b.push(a[i]);
+  }
+  return b;
+}
 
 
 // pluck
diff --git a/lib/date-ext.js b/lib/date-ext.js
index 472128c..1785fdd 100644
--- a/lib/date-ext.js
+++ b/lib/date-ext.js
@@ -1,16 +1,14 @@
+// batteries
+// Copyright 2010 - 2011 Sami Samhuri <sami@samhuri.net>
+
+var DateExt = { format: format };
+
 exports.extendNative = function() {
-    Object.keys(DateExt).forEach(function(k) {
-        if (Date.prototype[k]) return; // don't overwrite existing members
-        Date.prototype[k] = function() {
-            var fn = DateExt[k]
-              , args = [].slice.call(arguments)
-              ;
-            args.shift(this);
-            fn.apply(DateExt, args);
-        };
-    });
+  require('./ext').extend(Date, DateExt);
 };
 
+require('./object-ext').extend(exports, DateExt);
+
 var Weekdays = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday',
                 'Friday', 'Saturday'];
 
@@ -22,77 +20,77 @@ var Months = ['January', 'February', 'March', 'April', 'May', 'June', 'July',
 var MonthsShort = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug',
                    'Sep', 'Oct', 'Nov', 'Dec'];
 
+function format(d, fmt) {
+  return fmt.replace(/%(.)/, function(_, c) {
+      switch (c) {
+          case 'A': return Weekdays[d.getDay()];
+          case 'a': return WeekdaysShort[d.getDay()];
+          case 'B': return Months[d.getMonth()];
+          case 'b': // fall through
+          case 'h': return MonthsShort[d.getMonth()];
+          case 'D': return format(d, '%m/%d/%y');
+          case 'd': return pad(d.getDate());
+          case 'e': return d.getDate();
+          case 'F': return format(d, '%Y-%m-%d');
+          case 'H': return pad(d.getHours());
+          case 'I':
+              var hour = d.getHours();
+              if (hour == 0) hour = 12;
+              else if (hour > 12) hour -= 12;
+              return pad(hour);
+          case 'k': return pad(d.getHours(), ' ');
+          case 'l':
+              var hour = d.getHours();
+              if (hour == 0) hour = 12;
+              else if (hour > 12) hour -= 12;
+              return pad(hour, ' ');
+          case 'M': return pad(d.getMinutes());
+          case 'm': return pad(d.getMonth() + 1);
+          case 'n': return '\n';
+          case 'p': return d.getHours() < 12 ? 'AM' : 'PM';
+          case 'R': return format(d, '%H:%M');
+          case 'r': return format(d, '%I:%M:%S %p');
+          case 'S': return pad(d.getSeconds());
+          case 's': return d.getTime();
+          case 'T': return format(d, '%H:%M:%S');
+          case 't': return '\t';
+          case 'u':
+              var day = d.getDay();
+              return day == 0 ? 7 : day; // 1 - 7, Monday is first day of the week
+          case 'v': return format(d, '%e-%b-%Y');
+          case 'w': return d.getDay(); // 0 - 6, Sunday is first day of the week
+          case 'Y': return d.getFullYear();
+          case 'y':
+              var year = d.getYear();
+              return year < 100 ? year : year - 100;
+          case 'Z':
+              var tz = d.toString().match(/\((\w+)\)/);
+              return tz && tz[1] || '';
+          case 'z':
+              var off = d.getTimezoneOffset();
+              return (off < 0 ? '-' : '+') + pad(off / 60) + pad(off % 60);
+          default: return c;
+      }
+  });
+}
+
 function pad(n, padding) {
     padding = padding || '0';
     return n < 10 ? (padding + n) : n;
 }
 
-var DateExt = {
-    // FIXME write a c extension that uses strftime to do the heavy lifting
-    format: function(d, fmt) {
-        return fmt.replace(/%(.)/, function(_, c) {
-            switch (c) {
-                case 'A': return Weekdays[d.getDay()];
-                case 'a': return WeekdaysShort[d.getDay()];
-                case 'B': return Months[d.getMonth()];
-                case 'b': // fall through
-                case 'h': return MonthsShort[d.getMonth()];
-                case 'D': return DateExt.format(d, '%m/%d/%y');
-                case 'd': return pad(d.getDate());
-                case 'e': return d.getDate();
-                case 'F': return DateExt.format(d, '%Y-%m-%d');
-                case 'H': return pad(d.getHours());
-                case 'I':
-                    var hour = d.getHours();
-                    if (hour == 0) hour = 12;
-                    else if (hour > 12) hour -= 12;
-                    return pad(hour);
-                case 'k': return pad(d.getHours(), ' ');
-                case 'l':
-                    var hour = d.getHours();
-                    if (hour == 0) hour = 12;
-                    else if (hour > 12) hour -= 12;
-                    return pad(hour, ' ');
-                case 'M': return pad(d.getMinutes());
-                case 'm': return pad(d.getMonth() + 1);
-                case 'n': return '\n';
-                case 'p': return d.getHours() < 12 ? 'AM' : 'PM';
-                case 'R': return DateExt.format(d, '%H:%M');
-                case 'r': return DateExt.format(d, '%I:%M:%S %p');
-                case 'S': return pad(d.getSeconds());
-                case 's': return d.getTime();
-                case 'T': return DateExt.format(d, '%H:%M:%S');
-                case 't': return '\t';
-                case 'u':
-                    var day = d.getDay();
-                    return day == 0 ? 7 : day; // 1 - 7, Monday is first day of the week
-                case 'v': return DateExt.format(d, '%e-%b-%Y');
-                case 'w': return d.getDay(); // 0 - 6, Sunday is first day of the week
-                case 'Y': return d.getFullYear();
-                case 'y':
-                    var year = d.getYear();
-                    return year < 100 ? year : year - 100;
-                case 'Z':
-                    var tz = d.toString().match(/\((\w+)\)/);
-                    return tz && tz[1] || '';
-                case 'z':
-                    var off = d.getTimezoneOffset();
-                    return (off < 0 ? '-' : '+') + pad(off / 60) + pad(off % 60);
-                default: return c;
-            }
-        });
-    },
-    month: function(d) {
-        return Months(d.getMonth());
-    },
-    shortMonth: function(d) {
-        return MonthsShort(d.getMonth());
-    },
-    weekday: function(d) {
-        return Weekdays(d.getDay());
-    },
-    shortWeekday: function(d) {
-        return WeekdaysShort(d.getDay());
-    }
-};
-exports.DateExt = DateExt;
\ No newline at end of file
+function month(d) {
+  return Months(d.getMonth());
+}
+
+function shortMonth(d) {
+  return MonthsShort(d.getMonth());
+}
+
+function weekday(d) {
+  return Weekdays(d.getDay());
+}
+
+function shortWeekday(d) {
+  return WeekdaysShort(d.getDay());
+}
diff --git a/lib/ext.js b/lib/ext.js
index 17445d1..b8a04a6 100644
--- a/lib/ext.js
+++ b/lib/ext.js
@@ -1,13 +1,18 @@
+// batteries
+// Copyright 2010 - 2011 Sami Samhuri <sami@samhuri.net>
+
 exports.extend = function(obj, ext) {
-    // FIXME why doesn't this work when the caller supplies
-    // a native type's proto for obj? e.g. Array.prototype
-    Object.keys(ext).forEach(function(k) {
-        if (obj[k]) return; // don't overwrite existing members
-        obj[k] = function() {
-            var fn = ext[k]
-              , args = [].slice.call(arguments)
-              ;
-            fn.apply(null, args);
-        };
+  Object.keys(ext).forEach(function(k) {
+    if (k in obj.prototype) return; // don't overwrite existing members
+    var wrapper = function() {
+      var fn = ext[k]
+        , args = [].slice.call(arguments)
+        ;
+      args.unshift(this);
+      return fn.apply(this, args);
+    };
+    Object.defineProperty(obj.prototype, k, {
+      get: function() { return wrapper; }
     });
+  });
 };
diff --git a/lib/math-ext.js b/lib/math-ext.js
index 80618d6..5226c41 100644
--- a/lib/math-ext.js
+++ b/lib/math-ext.js
@@ -1,20 +1,26 @@
-exports.extendNative = function() {
-    Math.sum = sum;
-    Math.avg = avg;
+// batteries
+// Copyright 2010 - 2011 Sami Samhuri <sami@samhuri.net>
+
+var MathExt =
+{ avg: avg
+, sum: sum
+};
+
+exports.extendNative = function() {
+  Math.avg = avg;
+  Math.sum = sum;
 };
 
-exports.sum = sum;
 function sum() {
-    var nums = Array.isArray(arguments[0]) ? arguments[0] : arguments
-      , i = nums.length
-      , sum = 0
-      ;
-    while (i--) sum += arguments[i];
-    return sum;
+  var nums = Array.isArray(arguments[0]) ? arguments[0] : arguments
+    , i = nums.length
+    , sum = 0
+    ;
+  while (i--) sum += arguments[i];
+  return sum;
 }
 
-exports.avg = avg;
 function avg() {
-    var nums = Array.isArray(arguments[0]) ? arguments[0] : arguments;
-    return sum.call(this, nums) / nums.length;
+  var nums = Array.isArray(arguments[0]) ? arguments[0] : arguments;
+  return sum.call(this, nums) / nums.length;
 }
diff --git a/lib/object-ext.js b/lib/object-ext.js
index fe885b1..58facd7 100644
--- a/lib/object-ext.js
+++ b/lib/object-ext.js
@@ -1,10 +1,26 @@
-var ext = exports.ObjectExt = {
+// batteries
+// Copyright 2010 - 2011 Sami Samhuri <sami@samhuri.net>
 
-    cmp: function(a, b) {
-        if (a === b) return 0;
-        if (a < b) return -1;
-        if (a > b) return 1;
-        throw new Error('cannot effectively compare values');
-    }
+var ObjectExt =
+{ cmp: cmp
+, extend: extend
+}
 
+exports.extendNative = function() {
+  require('./ext').extend(Object, ObjectExt);
 };
+
+extend(module.exports, ObjectExt);
+
+function cmp(a, b) {
+  if (a === b) return 0;
+  if (a < b) return -1;
+  if (a > b) return 1;
+  throw new Error('cannot effectively compare values');
+}
+
+function extend(a, b) {
+  Object.getOwnPropertyNames(b).forEach(function(k) {
+    a[k] = b[k];
+  });
+}
diff --git a/lib/string-ext.js b/lib/string-ext.js
index f4873ee..1629202 100644
--- a/lib/string-ext.js
+++ b/lib/string-ext.js
@@ -1,11 +1,21 @@
-var StringExt = exports.StringExt = {
+// batteries
+// Copyright 2010 - 2011 Sami Samhuri <sami@samhuri.net>
 
-    cmp: function(a, b) {
-        if (a === b) return 0;
-        if (a < b) return -1;
-        return 1; // a > b
-    }
+// TODO
+// - reverse
+// - unpack
+// - sha1
 
-    // unpack
+var StringExt = { cmp: cmp };
 
+exports.extendNative = function() {
+  require('./ext').extend(String, StringExt);
 };
+
+require('./object-ext').extend(exports, StringExt);
+
+function cmp(a, b) {
+  if (a === b) return 0;
+  if (a < b) return -1;
+  return 1; // a > b
+}