Added full reduce capabilities not tested

lib/type/collection.js

@@ -146,6 +146,64 @@ exports.deepMap2 = function deepMap2(array1, array2, callback) {
   return res;
 };
 
+/**
+ * Reduce the given array to a scalar, applying a callback function to
+ * each pair of values, in the selected dimension.
+ * @param {Array | Matrix} mat
+ * @param {Integer} dimension
+ * @param {function} callback
+ * @return {Array | Matrix} res
+ */
+exports.reduce = function reduce (mat, dim, callback) {
+	if (mat instanceof Matrix) {
+		mat = mat.valueOf();
+	}
+	return _reduce(mat, dim, callback);
+}
+
+function _reduce(mat, dim, callback){
+	if(dim<=0){
+		if( typeof mat[0] === "number" ){
+			var i;
+			var val = mat[0];
+			for(i=0; i<mat.length; i++){
+				val = callback(val, mat[i]);
+			}
+			return val;
+		}else{
+			var tran = _switch(mat);
+			var i;
+			var ret = [];
+			for(i=0; i<tran.length; i++){
+				ret[i] = _reduce(tran[i], dim-1, callback);
+			}
+			return ret
+		}
+	}else{
+		var i;
+		var ret = [];
+		for(i=0; i<mat.length; i++){
+			ret[i] = _reduce(mat[i], dim-1, callback);
+		}
+		return ret;
+	}
+}
+
+function _switch(mat){
+    var I = mat.length;
+    var J = mat[0].length;
+    var i, j;
+    var ret = new Array();
+    for( j=0; j<J; j++) {
+        var tmp = new Array();
+        for( i=0; i<I; i++) {
+            tmp.push(mat[i][j]);
+        }
+        ret.push(tmp);
+    }
+    return ret;
+}
+
 /**
  * Recursively loop over all elements in a given multi dimensional array
  * and invoke the callback on each of the elements.