! character classification functions

dec isalpha, isupper, islower, isdigit, isxdigit, isalnum,
    isspace, ispunct, isctrl, isascii, isgraph : char -> bool;

dec tolower, toupper : char -> char;

! definitions for ASCII -- adjust for different character sets

--- isalpha c <= isupper c or islower c;
--- isupper c <= 'A' =< c and c =< 'Z';
--- islower c <= 'a' =< c and c =< 'z';
--- isdigit c <= '0' =< c and c =< '9';
--- isxdigit c <= isdigit c or 'a' =< c and c =< 'f' or 'A' =< c and c =< 'F';
--- isalnum c <= isalpha c or isdigit c;
--- isspace c <= c = ' ' or c = '\t' or c = '\n';
--- ispunct c <= isgraph c and c /= ' ' and not(isalnum c);
--- isctrl c <= isascii c and not(isgraph c);
--- isgraph c <= ' ' =< c and c =< '~';
--- isascii c <= ord c < 128;

--- tolower c <= if isupper c then chr(ord c + 32) else c;
--- toupper c <= if islower c then chr(ord c - 32) else c;