SIGNATURE Char

-- ASCII-Characters 

IMPORT  Nat ONLY nat 

SORT char

FUN     min max                         : char

FUN     pred succ                       : char -> char

FUN     tab newline blank vtab
        backspace return formfeed bell  : char

FUN     <= = >= < > |=                  : char**char->bool

FUN     lower?         -- abcdefghijklmnopqrstuvwxyz
        upper?         -- ABCDEFGHIJKLMNOPQRSTUVWXYZ
        control?       -- ^@^A^B^C^D^E^F^G^H^I^J^K^L^M^N^O
                       -- ^P^Q^R^S^T^U^V^W^X^Y^Z^[^\^]^^^_ DEL
        punctuation?   -- !"#$%&'()*+,-./ :;<=>?@ [\]^_` {|}~
        letter?        -- lower? or upper?
        digit?         -- 0123456789
        letgit?        -- letter? or digit?
        space?         -- newline tab blank
        whitespace?    -- space? formfeed return vtab
        printable?     -- blank  digit?  lower? upper? punctuation?
                                        : char->bool

FUN     lower upper                     : char -> char
        -- convert to corresponding upper- or lowercase letter
        -- identity if not lower? resp. upper?

FUN     !                               : denotation->char
        -- character denotation
        -- d! is undefined, if #(d) != 1