Concise way to say equal to set of values in C++

Question

For example I have the following string,

if (str[i] == \'(\' ||
    str[i] == \')\' ||
    str[i] == \'+\' ||
    str[i] == \'-\' ||
    str[i] == \'/\' ||
    s         


        

Answer 1

Not glorious because it is C instead of C++, but the C standard library is always accessible from C++ code, and my first idea as an old dinosaur would be:

if (strchr("()+-/*", str[i]) != NULL)

Simple and compact