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| procedure, pass(this)  | init (this, id, p1, p2, p3, p4) | 
|   | Create a quadrilateral element based upon four points.  
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| procedure, pass(this)  | facet_id (this, t, side) | 
|   | Return the edge id for face i as a 2-tuple t.  
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| procedure, pass(this)  | facet_order (this, t, side) | 
|   | Return the ordered edge for face i as a 2-tuple t.  
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| procedure, pass(this)  | diameter (this) | 
|   | Compute the diameter of a quadrilateral element.  
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| procedure, pass(this)  | centroid (this) | 
|   | Compute the centroid of a quadrilateral element.  
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| procedure, pass(this)  | equal (this, other) | 
|   | Check if two quad elements are equal.  
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|   | 
| generic  | operator (this, other) | 
|   | Check if two quad elements are equal.  
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|   | 
| procedure, pass(this)  | element (this, id, gdim, npts) | 
|   | Create an element with npts.  
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|   | 
| procedure, pass(this)  | free (this) | 
|   | Deallocate an element.  
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| procedure, pass(this)  | gdim (this) | 
|   | Get the geometric dimension of an element.  
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| procedure, pass(this)  | npts (this) | 
|   | Get the number of points in an element.  
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| procedure, pass(this)  | p (this, i) | 
|   | Return a pointer to point i of the element.  
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| procedure, pass(this)  | n_points (this) | 
|   | Get the number of points in an element.  
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| procedure, non_overridable, pass  | element_point (this, i) | 
|   | Return a pointer to point i of the element.  
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| procedure(element_equal), deferred, pass  | equal (this, other) | 
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| procedure(element_diameter), deferred, pass  | diameter (this) | 
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| procedure(element_centroid), deferred, pass  | centroid (this) | 
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| procedure(element_facet_id), deferred, pass  | facet_id (this, t, side) | 
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| procedure(element_facet_order), deferred, pass  | facet_order (this, t, side) | 
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| procedure, pass(this)  | id (this) | 
|   | Return the index of an entity.  
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| procedure, pass(this)  | set_id (this, id) | 
|   | Update the index of an entity.  
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|   | 
2D element composed of 4 points 
 Node numbering (NEKTON symmetric notation)
      3+-----+4    ^ s
       |     |     |
       |     |     |
      1+-----+2    +----> r 
Definition at line 58 of file quad.f90.