>Accessing an element of an array via ptr[3] is actually just short for (ptr + 3). This can be equivalently written as (3 + ptr) and therefore as 3[ptr], which

>Accessing an element of an array via ptr[3] is actually just short for (ptr + 3). This can be equivalently written as (3 + ptr) and therefore as 3[ptr], which turns out to be completely valid code. C++ standard defines the syntax of a postfix expression as this postfix-expression: primary-expression postfix-expression[expression] postfix-expression[braced-init-list] [expression]primary-expression is not valid