## Basic Operators Unlike C, Swift lets you perform remainder (%) calculations on floating-point numbers. ~~~ if x = y { // this is not valid, because x = y does not return a value } // Swift中的取模操作 -9 % 4 // equals -1，理解成：-9 = (4 × -2) + -1 ~~~ Swift also provides two identity operators (=== and !==), which you use to test whether two object references both refer to the same object instance ~~~ // ？？？ var arr1 = [1, 2, 3] var arr2 = arr1 arr2[0] = 10; arr1 // [10, 2, 3] arr2 // [10, 2, 3] arr1 === arr2 // 修改arr2，arr1也跟著修改，所以應該是指向一個object，這里應該是true，但結果卻是false ~~~