The Standard ML Basis Library

The PACK_REAL signature

Synopsis

signature PACK_REAL  (* OPTIONAL *)
structure PackRealBig :> PACK_REAL  (* OPTIONAL *)
  where type real = Real.real
structure PackRealLittle :> PACK_REAL  (* OPTIONAL *)
  where type real = Real.real
structure PackReal<N>Big :> PACK_REAL  (* OPTIONAL *)
  where type real = Real{N}.real
structure PackReal<N>Little :> PACK_REAL  (* OPTIONAL *)
  where type real = Real{N}.real


The PACK_REAL signature specifies the interface for packing and unpacking floating-point numbers into Word8 vectors and arrays. This provides a mechanism for transmitting floating-point values over a network.

For each optional Real<N> structure provided by an implementation, the implementation may also provide a pair of structures PackReal<N>Big and PackReal<N>Little. These structures share the real type defined in Real<N>. The PackReal<N>Big structures perform big-endian packing and unpacking, and the PackReal<N>Little structures perform little-endian packing and unpacking.

In addition, an implementation may provide the structures PackRealBig and PackRealLittle, which are aliases for the PACK_REAL structures related to the default Real structure.

Interface

type real
val bytesPerElem : int
val isBigEndian : bool
val toBytes   : real -> Word8Vector.vector
val fromBytes : Word8Vector.vector -> real
val subVec : Word8Vector.vector * int -> real
val subArr : Word8Array.array * int -> real
val update : Word8Array.array * int * real -> unit

Description

val bytesPerElem : int

The number of bytes per element, sufficient to store a value of type real.

isBigEndian

is true if the structure implements a big-endian view of the data.

val toBytes : real -> Word8Vector.vector
val fromBytes : Word8Vector.vector -> real

These functions pack and unpack floating-point values into and out of Word8Vector.vector values. The function fromBytes raises the Subscript exception if the argument vector does not have length at least bytesPerElem; otherwise the first bytesPerElem bytes are used.

subVec (seq, i)

subArr (seq, i)

These functions extract the subsequence

seq[bytesPerElem*i..bytesPerElem*(i+1)-1]

of the aggregate seq and convert it into a real value according to the endianness of the structure. They raise the Subscript exception if i < 0 or if Word8Array.length seq < bytesPerElem * (i + 1).

update (arr, i, r)

stores r into the bytes bytesPerElem*i through bytesPerElem*(i+1)-1 of the array arr, according to the structure's endianness. It raises the Subscript exception if i < 0 or if Word8Array.length arr < bytesPerElem * (i + 1).

See Also

PACK_WORD, REAL

Generated October 02, 2003
Last Modified May 28, 2000
Comments to John Reppy.

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