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1 definition found
 for cons cell
From The Free On-line Dictionary of Computing (30 December 2018) :

  cons cell
  
      /konz sel/ or /kons sel/ A Lisp pair object
     containing any two objects.  In Lisp, "cons" (short for
     "construct") is the fundamental operation for building structures
     such as lists and other binary trees.  The application of
     "cons" to objects H and T is written
  
     	(cons H T)
  
     and returns a pair object known as a "cons", "cons cell" or
     dotted pair.
  
     Typically, a cons would be stored in memory as a two consecutive
     pointers.
  
     The two objects in a cons, and the functions to extract them, are
     called "car" and "cdr" after two 15-bit fields of the machine
     code instruction format of the IBM 7090 that hosted the
     original LISP implementation.  These fields were called the
     "address" and "decrement" parts so "car" stood for "Contents of
     Address part of Register" and "cdr" for "Contents of Decrement
     part of Register".
  
     In the typical case where the cons holds one node of a list
     structure, the car is the head of the list (first element) and
     the cdr is the tail of the list (the rest).  If the list had
     only one element then the tail would be an empty list, represented
     by the cdr containing the special value "nil".
  
     To aid in working with nested structures such as lists of lists,
     Lisp provides functions to access the car of the car ("caar"), the
     car of the cdr ("cadr"), the cdr of the car ("cdar") and the cdr
     of the cdr ("cddr").
  
     (2014-11-09)
  

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