# Structure Word8

Identifier index | Structure index
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    (* Word8 -- SML Basis Library *)

    type word = word8

    val wordSize   : int

    val orb        : word * word -> word
    val andb       : word * word -> word
    val xorb       : word * word -> word
    val notb       : word -> word

    val <<         : word * Word.word -> word
    val >>         : word * Word.word -> word
    val ~>>        : word * Word.word -> word

    val +          : word * word -> word
    val -          : word * word -> word
    val *          : word * word -> word
    val div        : word * word -> word
    val mod        : word * word -> word

    val >          : word * word -> bool
    val <          : word * word -> bool
    val >=         : word * word -> bool
    val <=         : word * word -> bool
    val compare    : word * word -> order

    val min        : word * word -> word
    val max        : word * word -> word

    val toString   : word -> string
    val fromString : string -> word option
    val scan       : StringCvt.radix
                   -> (char, 'a) StringCvt.reader -> (word, 'a) StringCvt.reader
    val fmt        : StringCvt.radix -> word -> string

    val toInt      : word -> int
    val toIntX     : word -> int            (* with sign extension *)
    val fromInt    : int -> word

    val toLargeInt    : word -> int
    val toLargeIntX   : word -> int         (* with sign extension *)
    val fromLargeInt  : int -> word

    val toLargeWord   : word -> Word.word
    val toLargeWordX  : word -> Word.word   (* with sign extension *)
    val fromLargeWord : Word.word -> word

    (*
       [word] is the type of 8-bit words, or 8-bit unsigned integers in
       the range 0..255.

       [wordSize] equals 8.

       [orb(w1, w2)] returns the bitwise `or' of w1 and w2.

       [andb(w1, w2)] returns the bitwise `and' of w1 and w2.

       [xorb(w1, w2)] returns the bitwise `exclusive or' or w1 and w2.

       [notb w] returns the bitwise negation of w.

       [<<(w, k)] returns the word resulting from shifting w left by k
       bits.  The bits shifted in are zero, so this is a logical shift.
       Consequently, the result is 0-bits when k >= wordSize.

       [>>(w, k)] returns the word resulting from shifting w right by k
       bits.  The bits shifted in are zero, so this is a logical shift.
       Consequently, the result is 0-bits when k >= wordSize.

       [~>>(w, k)] returns the word resulting from shifting w right by k
       bits.  The bits shifted in are replications of the left-most bit:
       the `sign bit', so this is an arithmetical shift.  Consequently,
       for k >= wordSize and wordToInt w >= 0 the result is all 0-bits, and
       for k >= wordSize and wordToInt w <  0 the result is all 1-bits.

       To make <<, >>, and ~>> infix, use the declaration:
                              infix 5 << >> ~>>

       [+]
       [-]
       [*]
       [div]
       [mod] represent unsigned integer addition, subtraction,
       multiplication, division, and remainder, modulus 256.  The
       operations (i div j) and (i mod j) raise Div when j = 0.  Otherwise
       no exceptions are raised.

       [<]
       [<=]
       [>]
       [>=] compare words as unsigned integers.

       [compare(w1, w2)] returns LESS, EQUAL, or GREATER, according
       as w1 is less than, equal to, or greater than w2 (as unsigned integers).

       [min(w1, w2)] returns the smaller of w1 and w2 (as unsigned integers).

       [max(w1, w2)] returns the larger of w1 and w2 (as unsigned integers).

       [fmt radix w] returns a string representing w, in the radix (base)
       specified by radix.

         radix    description                     output format
         ------------------------------------------------------
          BIN     unsigned binary      (base  2)  [01]+
          OCT     unsigned octal       (base  8)  [0-7]+
          DEC     unsigned decimal     (base 10)  [0-9]+
          HEX     unsigned hexadecimal (base 16)  [0-9A-F]+

       [toString w] returns a string representing w in unsigned
       hexadecimal format.  Equivalent to (fmt HEX w).

       [fromString s] returns SOME(w) if a hexadecimal unsigned numeral
       can be scanned from a prefix of string s, ignoring any initial
       whitespace; returns NONE otherwise.  Raises Overflow if the scanned
       number cannot be represented as a word.  An unsigned hexadecimal
       numeral must have form, after possible initial whitespace:
           [0-9a-fA-F]+

       [scan radix {getc} charsrc] attempts to scan an unsigned numeral
       from the character source charsrc, using the accessor getc, and
       ignoring any initial whitespace.  The radix argument specifies the
       base of the numeral (BIN, OCT, DEC, HEX).  If successful, it
       returns SOME(w, rest) where w is the value of the numeral scanned,
       and rest is the unused part of the character source.  Raises
       Overflow if the scanned number cannot be represented as a word.  A
       numeral must have form, after possible initial whitespace:

         radix    input format
         -------------------------------------
          BIN     (0w)?[0-1]+
          OCT     (0w)?[0-7]+
          DEC     (0w)?[0-9]+
          HEX     (0wx|0wX|0x|0X)?[0-9a-fA-F]+

       [toInt w] returns the integer in the range 0..255 represented by w.

       [toIntX w] returns the signed integer (in the range ~128..127)
       represented by bit-pattern w.

       [fromInt i] returns the word holding the 8 least significant bits of i.

       [toLargeInt w] returns the integer in the range 0..255 represented by w.

       [toLargeIntX w] returns the signed integer (in the range ~128..127)
       represented by bit-pattern w.

       [fromLargeInt i] returns the word holding the 8 least significant bits of i.

       [toLargeWord w] returns the Word.word value corresponding to w.

       [toLargeWordX w] returns the Word.word value corresponding to w,
       with sign extension.  That is, the 8 least significant bits of the
       result are those of w, and the remaining bits are all equal to the
       most significant bit of w: its `sign bit'.

       [fromLargeWord w] returns w modulo 256.
    *)

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--- | ---

Moscow ML 2.00