More information available at: http://forge.scilab.org/index.php/p/json/
Introduction
============
JSON (JavaScript Object Notation) is a lightweight data-interchange format. It
is easy for humans to read and write. It is easy for machines to parse and
generate. It is based on a subset of the JavaScript Programming Language,
[Standard ECMA-262 3rd Edition - December 1999](http://www.ecma-international.org/publications/files/ecma-st/ECMA-262.pdf).
The JSON format is often used for serializing and transmitting structured data
over a network connection. It is primarily used to transmit data between a
server and web application, serving as an alternative to XML.
For more information, please read:
[http://json.org/](http://json.org/)
[http://en.wikipedia.org/wiki/Json](http://en.wikipedia.org/wiki/Json)
Structures:
===========
Since JSON supports key-value objects, the parser interprets the key-value JSON
objects as Scilab ``struct`` objects.
(Type ``help struct`` in Scilab for more information on Scilab structures.)
Consider the following example:
{
"orderID": 12345,
"shopperName": "John Smith",
"shopperEmail": "johnsmith@example.com",
"contents": [
{
"productID": 34,
"productName": "SuperWidget",
"quantity": 1
},
{
"productID": 56,
"productName": "WonderWidget",
"quantity": 3
}
],
"orderCompleted": true
}
Assuming the above JSON text is saved in a text file in the current working
directory, the text can be loaded into Scilab and parsed thus:
json_eg = mgetl("eg_1.json");
mystruct = JSONParse(json_eg)
This returns the following Scilab structure:
mystruct =
orderID: 12345
shopperName: "John Smith"
shopperEmail: "johnsmith@example.com"
contents: [1x2 struct]
orderCompleted: "%T"
Individual elements in the structure can be accessed thus:
Example 1:
-->mystruct.orderID
ans =
12345.
Example 2:
-->mystruct.contents.productName
ans =
ans(1)
SuperWidget
ans(2)
WonderWidget
Note that the JSON values of ``true``, ``false`` and ``null`` are represented in
Scilab as ``%T``, ``%F`` and ``%Nan``. Since Scilab contains a function called
``null()``, the function will be temporarily redefined by the parser. However,
the parser will restore the function after it is done parsing.
A Note About Matrices
=====================
A special aspect about this particular parser is the way it interprets vectors
and matrices:
JSON of the form:
"[1, 2, 3, 4, 5]"
is returned as a (row) vector is Scilab, as one might expect.
JSON of the form:
"[[1, 2, 3], [4, 5, 6], [7, 8, 9]]"
is returned as a two-dimensional matrix in Scilab:
1. 2. 3.
4. 5. 6.
7. 8. 9.
as one might expect, since the above JSON is fundamentally an example of a set
of arrays within an array. There is currently no support for hypermatrices. If
you need them, please add an [issue](http://forge.scilab.org/index.php/p/json/issues/create/)
and I'll consider adding support.
Proceeding with the above convention, a Scilab column vector would be defined in
JSON thus:
"[[1], [2], [3], [4]]"
which when parsed, returns this:
1.
2.
3.
4.
Other Notes
===========
* The parser takes into consideration JSON backslash-escapes. Except for the
backslash-quote, all other backslash-escapes are left as is as they do not
affect Scilab strings. Backslash-quotes are taken into consideration during the
parsing process.
* This version only has a parser. The next major version will include a JSON
encoder as well. Suggestions on this are welcome.
