Structures | Signatures | Identifiers

Signature BYTE

Conversion operations between Word8.word values and characters.

Bytes are 8-bit integers as provided by the Word8 structure, but serve the dual role as elements composing the extended ASCII character set. The Byte structure provides functions for converting values between these two roles. 
structure Byte : BYTE

signature BYTE = 
  sig
    val byteToChar      : Word8.word -> char
    val charToByte      : char -> Word8.word
    val bytesToString   : Word8Vector.vector -> string
    val stringToBytes   : string -> Word8Vector.vector
    val unpackStringVec : Word8VectorSlice.slice -> string
    val unpackString    : Word8ArraySlice.slice -> string
    val packString      : Word8Array.array * int * substring -> unit
  end
[byteToChar i]
returns the character whose code is i.

[charToByte c]
returns an 8-bit word holding the code for the character c.

[bytesToString v]
[stringToBytes s]
These functions convert between a vector of character codes and the corresponding string. Note that these functions do not perform end-of-line, or other character, translations. The semantics of these functions can be defined as follows, although one expects actual implementations will be more efficient: 
    fun bytesToString bv =
      CharVector.tabulate(
        Word8Vector.length bv,
        fn i => byteToChar(Word8Vector.sub(bv, i)))
    fun stringToBytes s =
      Word8Vector.tabulate(
        String.size s,
For implementations where the underlying representation of the Word8Vector.vector and string types are the same, these functions should be constant-time operations.

[unpackStringVec slice]
returns the string consisting of characters whose codes are held in the vector slice slice.

[unpackString slice]
returns the string consisting of characters whose codes are held in the array slice slice.

[packString (arr, i, s)]
puts the substring s into the array arr starting at offset i. It raises Subscript if i < 0 or size s + i > |arr|.

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