These avoid issues with out of range values for ctype.h functions

char_predicates.hpp

#ifndef CHAR_PREDICATES_HPP
#define CHAR_PREDICATES_HPP

[[nodiscard]] static inline bool
is_digit(int ch)
{
	return ((ch >= '0') && (ch <= '9'));
}

[[nodiscard]] static inline bool
is_alpha(int ch)
{
	const bool lower = (ch >= 'a') && (ch <= 'z');
	const bool upper = (ch >= 'A') && (ch <= 'Z');
	const bool either = lower || upper;
	return either;
}

[[nodiscard]] static inline bool
is_ident(int ch)
{
    const bool any = (is_digit(ch)) || (is_alpha(ch)) || (ch == '_');
    return any;
}

#endif