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(guile.info.gz) List Predicates

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 22.2.2 List Predicates
 ----------------------
 
 Often it is useful to test whether a given Scheme object is a list or
 not.  List-processing procedures could use this information to test
 whether their input is valid, or they could do different things
 depending on the datatype of their arguments.
 
  -- Scheme Procedure: list? x
  -- C Function: scm_list_p (x)
      Return `#t' iff X is a proper list, else `#f'.
 
    The predicate `null?' is often used in list-processing code to tell
 whether a given list has run out of elements.  That is, a loop somehow
 deals with the elements of a list until the list satisfies `null?'.
 Then, the algorithm terminates.
 
  -- Scheme Procedure: null? x
  -- C Function: scm_null_p (x)
      Return `#t' iff X is the empty list, else `#f'.
 
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