savejson.m

  json=savejson(rootname,obj,filename)
     or
  json=savejson(rootname,obj,opt)
  json=savejson(rootname,obj,'param1',value1,'param2',value2,...)

  convert a MATLAB object (cell, struct or array) into a JSON (JavaScript
  Object Notation) string

  author: Qianqian Fang (fangq<at> nmr.mgh.harvard.edu)
             created on 2011/09/09

  $Id: savejson.m 371 2012-06-20 12:43:06Z fangq $

  input:
       rootname: name of the root-object, if set to '', will use variable name
       obj: a MATLAB object (array, cell, cell array, struct, struct array)
       filename: a string for the file name to save the output JSON data
       opt: a struct for additional options, use [] if all use default
         opt can have the following fields (first in [.|.] is the default)

         opt.FileName [''|string]: a file name to save the output JSON data
         opt.FloatFormat ['%.10g'|string]: format to show each numeric element
                          of a 1D/2D array;
         opt.ArrayIndent [1|0]: if 1, output explicit data array with
                          precedent indentation; if 0, no indentation
         opt.ArrayToStruct[0|1]: when set to 0, savejson outputs 1D/2D
                          array in JSON array format; if sets to 1, an
                          array will be shown as a struct with fields
                          "_ArrayType_", "_ArraySize_" and "_ArrayData_"; for
                          sparse arrays, the non-zero elements will be
                          saved to _ArrayData_ field in triplet-format i.e.
                          (ix,iy,val) and "_ArrayIsSparse_" will be added
                          with a value of 1; for a complex array, the 
                          _ArrayData_ array will include two columns 
                          (4 for sparse) to record the real and imaginary 
                          parts, and also "_ArrayIsComplex_":1 is added. 
         opt.ParseLogical [0|1]: if this is set to 1, logical array elem
                          will use true/false rather than 1/0.
         opt.NoRowBracket [1|0]: if this is set to 1, arrays with a single
                          numerical element will be shown without a square
                          bracket, unless it is the root object; if 0, square
                          brackets are forced for any numerical arrays.
         opt.ForceRootName [0|1]: when set to 1 and rootname is empty, savejson
                          will use the name of the passed obj variable as the 
                          root object name; if obj is an expression and 
                          does not have a name, 'root' will be used; if this 
                          is set to 0 and rootname is empty, the root level 
                          will be merged down to the lower level.
         opt.Inf ['"$1_Inf_"'|string]: a customized regular expression pattern
                          to represent +/-Inf. The matched pattern is '([-+]*)Inf'
                          and $1 represents the sign. For those who want to use
                          1e999 to represent Inf, they can set opt.Inf to '$11e999'
         opt.NaN ['"_NaN_"'|string]: a customized regular expression pattern
                          to represent NaN
         opt.JSONP [''|string]: to generate a JSONP output (JSON with padding),
                          for example, if opt.JSON='foo', the JSON data is
                          wrapped inside a function call as 'foo(...);'
         opt.UnpackHex [1|0]: conver the 0x[hex code] output by loadjson 
                          back to the string form
         opt can be replaced by a list of ('param',value) pairs. The param 
         string is equivallent to a field in opt.
  output:
       json: a string in the JSON format (see http://json.org)

  examples:
       a=struct('node',[1  9  10; 2 1 1.2], 'elem',[9 1;1 2;2 3],...
            'face',[9 01 2; 1 2 3; NaN,Inf,-Inf], 'author','FangQ');
       savejson('mesh',a)
       savejson('',a,'ArrayIndent',0,'FloatFormat','\t%.5g')

 -- this function is part of jsonlab toolbox (http://iso2mesh.sf.net/cgi-bin/index.cgi?jsonlab)