Info Catalog eintr: setcar eintr: car cdr & cons eintr: cons Exercise

eintr: setcdr

 
 7.6 ‘setcdr’
 ============
 
 The ‘setcdr’ function is similar to the ‘setcar’ function, except that
 the function replaces the second and subsequent elements of a list
 rather than the first element.
 
    (To see how to change the last element of a list, look ahead to 
 The ‘kill-new’ function kill-new function, which uses the ‘nthcdr’ and
 ‘setcdr’ functions.)
 
    To see how this works, set the value of the variable to a list of
 domesticated animals by evaluating the following expression:
 
      (setq domesticated-animals '(horse cow sheep goat))
 
 If you now evaluate the list, you will be returned the list ‘(horse cow
 sheep goat)’:
 
      domesticated-animals
           ⇒ (horse cow sheep goat)
 
    Next, evaluate ‘setcdr’ with two arguments, the name of the variable
 which has a list as its value, and the list to which the CDR of the
 first list will be set;
 
      (setcdr domesticated-animals '(cat dog))
 
 If you evaluate this expression, the list ‘(cat dog)’ will appear in the
 echo area.  This is the value returned by the function.  The result we
 are interested in is the side effect, which we can see by evaluating the
 variable ‘domesticated-animals’:
 
      domesticated-animals
           ⇒ (horse cat dog)
 
 Indeed, the list is changed from ‘(horse cow sheep goat)’ to ‘(horse cat
 dog)’.  The CDR of the list is changed from ‘(cow sheep goat)’ to ‘(cat
 dog)’.
 

Info Catalog eintr: setcar eintr: car cdr & cons eintr: cons Exercise