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From - Fri Sep 24 14:13:45 1999
Message-ID: <367A9894.7DE14518@icparc.ic.ac.uk>
Date: Fri, 18 Dec 1998 18:01:56 +0000
From: Joachim Schimpf <js10@icparc.ic.ac.uk>
Organization: IC-Parc, Imperial College, London
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To: sn10, ks15
Subject: EXDR format
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-- 
------------------------------------------------------------------------
 Joachim Schimpf                /               phone: +44 171 594 8187
 IC-Parc, Imperial College     /              mailto:J.Schimpf@ic.ac.uk
 London SW7 2AZ, UK           /      http://www.icparc.ic.ac.uk/eclipse

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EXDR interchange format
============================================================

We have defined a data interchange format called EXDR for the
communication between ECLiPSe and other languages.
The data types available in this format are Integer, Double,
String, List, Nil and Structure. The mapping onto different
languages is as follows:

EXDR type	ECLiPSe type	TCL type	VB type
-----------------------------------------------------------
Integer		integer		int
		123		123

Double		real		double
		12.3		12.3

String		string		string
		"abc"		abc

List		./2		list
		[a,b,c]		{a b c}
				"a b c"

Nil		[]/0		empty string
		[]		{} ""

Struct		compound	list
		foo(bar,3)	{foo bar 3}


Language primitives to read/write EXDR terms
============================================================

Eclipse predicates:

    write_exdr(+Stream, ++Term)

    	This predicate writes terms in exdr format.
	Term must be ground and can contain structures, lists, atoms,
	strings, (double) floats and (short) integers.
	It uses the "natural" types of the Eclipse terms.
	Atoms are written as structures of arity 0 (not as strings).

    read_exdr(+Stream, -Term)

    	This predicate reads exdr format and constructs an Eclipse term.


Tcl procedures:

    ec_read_exdr channel
    
    	Reads one term in exdr format. 


    ec_write_exdr channel ?format? term

    	Writes one term in exdr format. Types are specified as follows:

	To create	Use
	EXDR type	<format>	term required

	String		S		string
	Integer		I		integer
	Double		D		double
	List		[<formats>]	list of certain length
	List		[<formats>*]	list
	Struct		(<formats>)	list of certain length
	Struct		(<formats>*)	list

	e.g. Tcl command				results in Eclipse term

	ec_write_exdr ec_queue6	S hello			"hello"
	ec_write_exdr ec_queue6	() hello		hello
	ec_write_exdr ec_queue6	S 123			"123"
	ec_write_exdr ec_queue6	I 123			123
	ec_write_exdr ec_queue6	D 123			123.0
	ec_write_exdr ec_queue6	() 123			'123'
	ec_write_exdr ec_queue6	{[SID]} {a 3 4.5}	["a", 3, 4.5]
	ec_write_exdr ec_queue6	{[I*]} {1 2 3 4}	[1, 2, 3, 4]
	ec_write_exdr ec_queue6	{(I*)} {f 1 2 3}	f(1,2,3)

	The format argument defaults to S.


Serialized representation of EXDR terms (EXDR_VERSION 1)
============================================================

This is what we actually send over the communication channels:

    Term	::=	'V' Version (Integer|Double|String|List|Nil|Struct)
    Integer	::=	'I' <xdr_int>
    Double	::=	'D' <xdr_double>
    String	::=	'S' Length <byte>*
    List 	::=	'[' Term (List|Nil)
    Nil	 	::=	']'
    Struct	::=	'F' Arity String Term*
    Length	::=	<xdr_int>			// >= 0
    Arity	::=	<xdr_int>			// >= 0
    Version	::=	<byte>
    <xdr_int>	::=	4 bytes, msb first
    <xdr_double>::=	8 bytes, ieee double, exponent first


--------------4487EB716201DD5652BFA1D7--


From - Fri Sep 24 14:14:08 1999
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To: js10@icparc.ic.ac.uk, ks15@icparc.ic.ac.uk
Subject: Exdr  - including VB
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From: Stefano Novello <sn10@icparc.ic.ac.uk>
Date: Wed, 13 Jan 1999 15:06:27 +0000
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EXDR interchange format
============================================================

We have defined a data interchange format called EXDR for the
communication between ECLiPSe and other languages.
The data types available in this format are Integer, Double,
String, List, Nil and Structure. The mapping onto different
languages is as follows:

EXDR type	ECLiPSe type	TCL type	VB type
-----------------------------------------------------------
Integer		integer		int		Long
		123		123		123

Double		real		double		Double
		12.3		12.3		12.3

String		string		string		String
		"abc"		abc		"abc"

List		./2		list		Collection of variant
		[a,b,c]		{a b c}
				"a b c"

Nil		[]/0		empty string	Empty Collection of variant
		[]		{} ""		

Struct		compound	list		Array of variant
		foo(bar,3)	{foo bar 3}	functor at index 0


Language primitives to read/write EXDR terms
============================================================

Eclipse predicates:

    write_exdr(+Stream, ++Term)

    	This predicate writes terms in exdr format.
	Term must be ground and can contain structures, lists, atoms,
	strings, (double) floats and (short) integers.
	It uses the "natural" types of the Eclipse terms.
	Atoms are written as structures of arity 0 (not as strings).

    read_exdr(+Stream, -Term)

    	This predicate reads exdr format and constructs an Eclipse term.


Tcl procedures:

    ec_read_exdr channel
    
    	Reads one term in exdr format. 


    ec_write_exdr channel ?format? term

    	Writes one term in exdr format. Types are specified as follows:

	To create	Use
	EXDR type	<format>	term required

	String		S		string
	Integer		I		integer
	Double		D		double
	List		[<formats>]	list of certain length
	List		[<formats>*]	list
	Struct		(<formats>)	list of certain length
	Struct		(<formats>*)	list

	e.g. Tcl command				results in Eclipse term

	ec_write_exdr ec_queue6	S hello			"hello"
	ec_write_exdr ec_queue6	() hello		hello
	ec_write_exdr ec_queue6	S 123			"123"
	ec_write_exdr ec_queue6	I 123			123
	ec_write_exdr ec_queue6	D 123			123.0
	ec_write_exdr ec_queue6	() 123			'123'
	ec_write_exdr ec_queue6	{[SID]} {a 3 4.5}	["a", 3, 4.5]
	ec_write_exdr ec_queue6	{[I*]} {1 2 3 4}	[1, 2, 3, 4]
	ec_write_exdr ec_queue6	{(I*)} {f 1 2 3}	f(1,2,3)

	The format argument defaults to S.

Visual Basic methods:
Methods of the EclipseStream class

sub WriteExdr(v as Variant)
	Does a default conversion
	long -> int
	double -> double
	string -> string
	collection -> list
	array -> structure

sub WriteExdrHead()
sub WriteExdrInt(Long i)
sub WriteExdrFloat(Double d)
sub WriteExdrString(String s)
sub WriteExdrAtom(String s)
sub WriteExdrStruct(String functor,Long arity)
sub WriteExdrLopen()
sub WriteExdrLclose()

function ReadExdr() as Variant

Serialized representation of EXDR terms (EXDR_VERSION 1)
============================================================

This is what we actually send over the communication channels:

    Term	::=	'V' Version (Integer|Double|String|List|Nil|Struct)
    Integer	::=	'I' <xdr_int>
    Double	::=	'D' <xdr_double>
    String	::=	'S' Length <byte>*
    List 	::=	'[' Term (List|Nil)
    Nil	 	::=	']'
    Struct	::=	'F' Arity String Term*
    Length	::=	<xdr_int>			// >= 0
    Arity	::=	<xdr_int>			// >= 0
    Version	::=	<byte>
    <xdr_int>	::=	4 bytes, msb first
    <xdr_double>::=	8 bytes, ieee double, exponent first