How can it be valid implementation of isxdigit? ``` int isxdigit(int c) { if (c == EOF) { return false; } return some_a

How can it be valid implementation of isxdigit? ``` int isxdigit(int c) { if (c == EOF) { return false; } return some_array[c]; } ``` If you write code like this, then everything in programming is UB.