Check if s is an uppercased ASCII string.
ditto
assert(`A`.isUppercasedASCII); assert(!`a`.isUppercasedASCII); assert(!`alpha`.isUppercasedASCII); assert(`ALPHA`.isUppercasedASCII); assert(!`aThing`.isUppercasedASCII); assert(!`Alpha`.isUppercasedASCII); assert(!`Jack London`.isUppercasedASCII);
See Implementation
Check if s is an uppercased ASCII string.