text: /*  value_equals.js
      
      The MIT License (MIT)
      
      Copyright (c) 2013-2020, Reactive Sets
      
      Permission is hereby granted, free of charge, to any person obtaining a copy
      of this software and associated documentation files (the "Software"), to deal
      in the Software without restriction, including without limitation the rights
      to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
      copies of the Software, and to permit persons to whom the Software is
      furnished to do so, subject to the following conditions:
      
      The above copyright notice and this permission notice shall be included in all
      copies or substantial portions of the Software.
      
      THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
      IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
      FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
      AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
      LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
      OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
      SOFTWARE.
  */
  export function value_equals(a, b, enforce_properties_order, cyclic) {
    'use strict';
    
    var toString = Object.prototype.toString;
    
    return equals(a, b, enforce_properties_order, cyclic);
    
    /* --------------------------------------------------------------------------
        @function value_equals( a, b, enforce_properties_order, cyclic )
        
        @short Returns true if a and b are deeply equal, false otherwise.
        
        @parameters
        - **a** (Any type): value to compare to ```b```
        - **b** (Any type): value compared to ```a```
        - **enforce_properties_order** (Boolean): true to check if Object
          properties are provided in the same order between ```a``` and
          ```b```
        - **cyclic** (Boolean): true to check for cycles in cyclic objects
        
        @description
        Implementation:
        ```a``` is considered equal to ```b``` if all scalar values in
        a and b are strictly equal as compared with operator '===' except
        for these two special cases:
        - ```0 === -0``` but are not considered equal by value_equals().
        - ```NaN``` is not equal to itself but is considered equal by
        value_equals().
        
        ```RegExp``` objects must have the same ```lastIndex``` to be
        considered equal. i.e. both regular expressions have matched
        the same number of times.
        
        Functions must be identical, so that they have the same closure
        context.
        
        ```undefined``` is a valid value, including in Objects
        
        This function is checked by 106 CI tests.
        
        Provide options for slower, less-common use cases:
        
        - Unless enforce_properties_order is true, if ```a``` and ```b```
          are non-Array Objects, the order of occurence of their attributes
          is considered irrelevant: ```{ a: 1, b: 2 }``` is considered equal
          to ```{ b: 2, a: 1 }```.
        
        - Unless cyclic is true, Cyclic objects will throw a
          ```RangeError``` exception: ```"Maximum call stack size exceeded"```
    */
    function equals( a, b, enforce_properties_order, cyclic ) {
      return a === b       // strick equality should be enough unless zero
        && a !== 0         // because 0 === -0, requires test by _equals()
        || _equals( a, b ) // handles not strictly equal or zero values
      ;
      
      function _equals( a, b ) {
        // a and b have already failed test for strict equality or are zero
        
        var s, l, p, x, y;
        
        // They should have the same toString() signature
        if ( ( s = toString.call( a ) ) !== toString.call( b ) ) return false;
        
        switch( s ) {
          default: // Boolean, Date, String
            return a.valueOf() === b.valueOf();
          
          case '[object Number]':
            // Converts Number instances into primitive values
            // This is required also for NaN test bellow
            a = +a;
            b = +b;
            
            return a ?         // a is Non-zero and Non-NaN
                a === b
              :                // a is 0, -0 or NaN
                a === a ?      // a is 0 or -O
                1/a === 1/b    // 1/0 !== 1/-0 because Infinity !== -Infinity
              : b !== b        // NaN, the only Number not equal to itself!
            ;
          // [object Number]
          
          case '[object RegExp]':
            return a.source   == b.source
              && a.global     == b.global
              && a.ignoreCase == b.ignoreCase
              && a.multiline  == b.multiline
              && a.lastIndex  == b.lastIndex
            ;
          // [object RegExp]
          
          case '[object Function]':
            return false; // functions should be strictly equal because of closure context
          // [object Function]
          
          case '[object Array]':
            if ( cyclic && ( x = reference_equals( a, b ) ) !== null ) return x; // intentionally duplicated bellow for [object Object]
            
            if ( ( l = a.length ) != b.length ) return false;
            // Both have as many elements
            
            while ( l-- ) {
              if ( ( x = a[ l ] ) === ( y = b[ l ] ) && x !== 0 || _equals( x, y ) ) continue;
              
              return false;
            }
            
            return true;
          // [object Array]
          
          case '[object Object]':
            if ( cyclic && ( x = reference_equals( a, b ) ) !== null ) return x; // intentionally duplicated from above for [object Array]
            
            l = 0; // counter of own properties
            
            if ( enforce_properties_order ) {
              var properties = [];
              
              for ( p in a ) {
                if ( a.hasOwnProperty( p ) ) {
                  properties.push( p );
                  
                  if ( ( x = a[ p ] ) === ( y = b[ p ] ) && x !== 0 || _equals( x, y ) ) continue;
                  
                  return false;
                }
              }
              
              // Check if 'b' has as the same properties as 'a' in the same order
              for ( p in b )
                if ( b.hasOwnProperty( p ) && properties[ l++ ] != p )
                  return false;
            } else {
              for ( p in a ) {
                if ( a.hasOwnProperty( p ) ) {
                  ++l;
                  
                  if ( ( x = a[ p ] ) === ( y = b[ p ] ) && x !== 0 || _equals( x, y ) ) continue;
                  
                  return false;
                }
              }
              
              // Check if 'b' has as not more own properties than 'a'
              for ( p in b )
                if ( b.hasOwnProperty( p ) && --l < 0 )
                  return false;
            }
            
            return true;
          // [object Object]
        } // switch toString.call( a )
      } // _equals()
      
      /* -----------------------------------------------------------------------------------------
         reference_equals( a, b )
         
         Helper function to compare object references on cyclic objects or arrays.
         
         Returns:
           - null if a or b is not part of a cycle, adding them to object_references array
           - true: same cycle found for a and b
           - false: different cycle found for a and b
         
         On the first call of a specific invocation of equal(), replaces self with inner function
         holding object_references array object in closure context.
         
         This allows to create a context only if and when an invocation of equal() compares
         objects or arrays.
      */
      function reference_equals( a, b ) {
        var object_references = [];
        
        return ( reference_equals = _reference_equals )( a, b );
        
        function _reference_equals( a, b ) {
          var l = object_references.length;
          
          while ( l-- )
            if ( object_references[ l-- ] === b )
              return object_references[ l ] === a;
          
          object_references.push( a, b );
          
          return null;
        } // _reference_equals()
      } // reference_equals()
    } // equals()
  }; // value_equals.js