NAME
Muldis::D::Core::Cast - Muldis D explicit type-casting operators
VERSION
This document is Muldis::D::Core::Cast version 0.129.0.
PREFACE
This document is part of the Muldis D language specification, whose root document is Muldis::D; you should read that root document before you read this one, which provides subservient details. Moreover, you should read the Muldis::D::Core document before this current document, as that forms its own tree beneath a root document branch.
DESCRIPTION
This document's purpose is to consolidate all the core Muldis D type-casting routines that are conceptually monadic functions between 2 core types. It also declares a few special data types that support them.
This documentation is pending.
TYPE SUMMARY
Following are all the data types described in this document, arranged in a type graph according to their proper sub|supertype relationships:
sys.std.Core.Type.Universal
sys.std.Core.Type.Scalar
sys.std.Core.Type.DHScalar
sys.std.Core.Type.Int
sys.std.Core.Type.NNInt
sys.std.Core.Type.PInt
# These are all finite integer types.
sys.std.Core.Type.Cast.PInt1_4
sys.std.Core.Type.Cast.PInt2_36This documentation is pending.
DATA TYPES FOR ENCODING SCALARS AS TEXTS
sys.std.Core.Type.Cast.PInt1_4
PInt1_4 is a proper subtype of PInt where all member values are between 1 and 4. Its maximum value is 4. The cardinality of this type is 4.
sys.std.Core.Type.Cast.PInt2_36
PInt2_36 is a proper subtype of PInt where all member values are between 2 and 36. (The significance of the number 36 is 10 digits plus 26 letters.) Its default value is 10 (to correspond to base-10 being the default base for numeric literals in the STD dialects when no explicit base is given); its minimum and maximum values are 2 and 36, respectively. The cardinality of this type is 35.
FUNCTIONS FOR CASTING BETWEEN TUPLES AND SINGLE-TUPLE RELATIONS
sys.std.Core.Cast.Tuple_from_Relation
function sys.std.Core.Cast.Tuple_from_Relation (Tuple <-- $topic : Relation) {...}
This function results in the Tuple that is the sole member tuple of its argument. This function will fail if its argument does not have exactly one tuple. Note that this operation is also known as t.
sys.std.Core.Cast.Relation_from_Tuple
function sys.std.Core.Cast.Relation_from_Tuple (Relation <-- $topic : Tuple) {...}
This function results in the Relation value those body has just the one Tuple that is its argument. Note that this operation is also known as r.
FUNCTIONS FOR CASTING BETWEEN CANONICAL SETS AND BAGS
sys.std.Core.Cast.Set_from_Bag
function sys.std.Core.Cast.Set_from_Bag (Set <-- $topic : Bag) {...}
This function results in the Set that is the projection of the value attribute of its Bag argument.
sys.std.Core.Cast.Bag_from_Set
function sys.std.Core.Cast.Bag_from_Set (Bag <-- $topic : Set) {...}
This function results in the Bag that is the extension of its Set argument with a new count attribute whose value for every tuple is 1.
FUNCTIONS FOR CASTING BETWEEN INTEGERS AND RATIONALS
These functions convert between Rat values and equal or nearly equal Int values.
sys.std.Core.Cast.Int_from_Rat
function sys.std.Core.Cast.Int_from_Rat (Int <-- $rat : Rat, $round_meth : RoundMeth) {...}
This selector function results in the Int value that is conceptually equal to or otherwise nearest to its rat argument, where the nearest is determined by the rounding method specified by the round_meth argument.
sys.std.Core.Cast.Rat_from_Int
function sys.std.Core.Cast.Rat_from_Int (Rat <-- $int : Int) {...}
This selector function results in the Rat value that is conceptually equal to its Int argument.
FUNCTIONS FOR ENCODING INTEGERS AS TEXTS
These functions convert between Int values and canonically formatted representations of integers as character strings.
sys.std.Core.Cast.Int_from_Text
function sys.std.Core.Cast.Int_from_Text (Int <-- $text : Text, $radix? : PInt2_36) {...}
This selector function results in the Int value that its (not-empty) text argument maps to when the whole character string is evaluated as a base-radix integer. Extending the typical formats of [base-2, base-8, base-10, base-16], this function supports base-2 through base-36; to get the latter, the characters 0-9 and A-Z represent values in 0-35. This function will fail if text can't be mapped as specified.
sys.std.Core.Cast.Text_from_Int
function sys.std.Core.Cast.Text_from_Int (Text <-- $int : Int, $radix? : PInt2_36) {...}
This selector function results in the (not-empty) Text value where its int argument is formatted as a base-radix integer.
FUNCTIONS FOR ENCODING RATIONALS AS TEXTS
These functions convert between Rat values and canonically formatted representations of rationals as character strings.
sys.std.Core.Cast.Rat_from_Text
function sys.std.Core.Cast.Rat_from_Text (Rat <-- $text : Text, $radix? : PInt2_36) {...}
This selector function results in the Rat value that its (not-empty) text argument maps to when the whole character string is evaluated as a base-radix rational. Extending the typical formats of [base-2, base-8, base-10, base-16], this function supports base-2 through base-36; to get the latter, the characters 0-9 and A-Z represent values in 0-35. This function will fail if text can't be mapped as specified.
sys.std.Core.Cast.Text_from_Rat
function sys.std.Core.Cast.Text_from_Rat (Text <-- $rat : Rat, $radix? : PInt2_36) {...}
This selector function results in the (not-empty) Text value where its rat argument is formatted as a base-radix rational.
FUNCTIONS FOR ENCODING BLOBS AS TEXTS
These functions convert between Blob values and canonically formatted representations of binary strings as character strings.
sys.std.Core.Cast.Blob_from_Text
function sys.std.Core.Cast.Blob_from_Text (Blob <-- $text : Text, $size : PInt1_4) {...}
This selector function results in the Blob value that its text argument maps to when each input character represents a sequence of 1-4 bits, the number of bits per character being determined by the size argument; for example, if size is 1, then each input character is a [0-1] and represents a bit; or, if size is 4, then each input character is a [0-9A-F] and represents 4 bits. This function will fail if text can't be mapped as specified.
sys.std.Core.Cast.Text_from_Blob
function sys.std.Core.Cast.Text_from_Blob (Text <-- $blob : Blob, $size : PInt1_4) {...}
This selector function results in the Text value where its argument is encoded using a character for each sequence of 1-4 bits, the number of bits per character being determined by the size argument. This function will fail if blob doesn't have a length in bits which is a multiple of size.
FUNCTIONS FOR ENCODING INTEGERS AS BLOBS
These functions convert between Int values and canonically formatted representations of integers as binary strings. Conjecture: These may not actually be useful, and perhaps only operators that take an argument specifying a fixed-length field size, with big and little endian versions, would be appropriate instead. Or maybe both kinds are necessary.
sys.std.Core.Cast.Int_from_Blob_S_VBE
function sys.std.Core.Cast.Int_from_Blob_S_VBE (Int <-- $blob : Blob) {...}
This selector function results in the Int value that its blob argument maps to when the whole bit string is treated literally as a variable-length binary (two's complement) signed integer of 1 or more bits in length. The first bit is taken as the sign bit, and any other bits provide greater precision than the -1 thru 0 range. The bit string is assumed to be big-endian, since it may not be possible to use little-endian in situations where the bit length isn't a multiple of 8.
sys.std.Core.Cast.Blob_S_VBE_from_Int
function sys.std.Core.Cast.Blob_S_VBE_from_Int (Blob <-- $int : Int) {...}
This selector function results in the Blob value where its int argument is formatted as a variable-length binary (two's complement) signed integer of 1 or more bits in length; the smallest number of bits necessary to store int is used.
sys.std.Core.Cast.Int_from_Blob_U_VBE
function sys.std.Core.Cast.Int_from_Blob_U_VBE (NNInt <-- $blob : Blob) {...}
This function is the same as sys.std.Core.Cast.Int_from_Blob_S_VBE but that it does unsigned integers.
sys.std.Core.Cast.Blob_U_VBE_from_Int
function sys.std.Core.Cast.Blob_U_VBE_from_Int (NNInt <-- $blob : Blob) {...}
This function is the same as sys.std.Core.Cast.Blob_S_VBE_from_Int but that it does unsigned integers.
SEE ALSO
Go to Muldis::D for the majority of distribution-internal references, and Muldis::D::SeeAlso for the majority of distribution-external references.
AUTHOR
Darren Duncan (darren@DarrenDuncan.net)
LICENSE AND COPYRIGHT
This file is part of the formal specification of the Muldis D language.
Muldis D is Copyright © 2002-2010, Muldis Data Systems, Inc.
See the LICENSE AND COPYRIGHT of Muldis::D for details.
TRADEMARK POLICY
The TRADEMARK POLICY in Muldis::D applies to this file too.
ACKNOWLEDGEMENTS
The ACKNOWLEDGEMENTS in Muldis::D apply to this file too.