Reorder functions alphabetically, add the identity and function composition and finally rename defaultCompare into compare and make it take a comparison as argument, defaulting to the identity

fun.js

@@ -1,7 +1,9 @@
 function Fun() {
 	return {
-		defaultCompare: defaultCompare,
+		compare: compare,
+		compose: compose,
 		defined: defined,
+		id: id,
 		insert: insert,
 		map: map,
 		mapFilter: mapFilter,
@@ -9,10 +11,32 @@ function Fun() {
 		proj: proj
 	};
 
-	function insert(obj, t, compare, min, max) {
-		min = min == undefined ? 0 : min;
-		max = max == undefined ? t.length : max;
-		compare = compare == undefined ? defaultCompare : compare;
+	function compare(on) {
+		on = on || id;
+		return function(a, b) {
+			var va = on(a), vb = on(b);
+			return va < vb ? -1 : (va > vb ? 1 : 0)
+		};
+	}
+
+	function compose(f, g) {
+		return function() {
+			return g(f.apply(null, arguments));
+		};
+	}
+
+	function defined(x) {
+		return x != undefined;
+	}
+
+	function id(x) {
+		return x;
+	}
+
+	function insert(obj, t, comparer, min, max) {
+		min = defined(min) ? min : 0;
+		max = defined(max) ? max : t.length;
+		comparer = comparer || compare();
 		if(max - min < 1) {
 			return min;
 		}
@@ -24,16 +48,6 @@ function Fun() {
 		}
 	}
 
-	function defaultCompare(a, b) {
-		if(a < b) {
-			return -1;
-		} else if(a > b) {
-			return 1;
-		} else {
-			return 0;
-		}
-	}
-
 	function map(mapper, f) {
 		return function() {
 			var args = Array.prototype.map.call(arguments, mapper);
@@ -41,14 +55,6 @@ function Fun() {
 		}
 	}
 
-	function of(o) {
-		return function(key) {return o[key];};
-	}
-
-	function proj(key) {
-		return function(o) {return o[key];};
-	}
-
 	function mapFilter(mapper, predicate) {
 		return function(array) {
 			return array.reduce(function(accumulator, elem) {
@@ -58,7 +64,11 @@ function Fun() {
 		};
 	}
 
-	function defined(x) {
-		return x != undefined;
+	function of(o) {
+		return function(key) {return o[key];};
+	}
+
+	function proj(key) {
+		return function(o) {return o[key];};
 	}
 }