LISP

THE FIRST FUNCTIONAL LANGUAGE: LISP
The oldest and most widely used functional language is Lisp

DATA TYPES AND STRUCTURES
  • There are 2 types of data objects in the original Lisp: atoms and lists.
  • Atoms, which have the form of identifiers, are the symbols of Lisp
  • Numeric constants are also considered atoms
  • Lisp rarely requires the operations of insertions or deletions
  • Lists are specified by delimiting their elements within parentheses
                         Ex,      (A B C D)
  • Nested list structures are also specified by parentheses
                         Ex,      (A (B C) D (E (F G)))
  • The above list contains 4 elements:  the first element is A, the second is (B C), the third is D and the fourth is (E (F G))
  • Internally, lists are usually stored as single-linked list structures, in which each node has 2 pointers and represents an element

THE FIRST LISP INTERPRETER
  • The first requirements for the universal Lisp function was a notation that allowed functions to be expressed in the same way data was expressed
  • Function calls are specified in a prefix list form
                      Ex, (function_name         arg_1 … arg_n)
  • ex, if a + is a function that takes 2 numeric parameters,    ( +  5  7)   evaluates to 12.
  • The function Evaluation could evaluate any other function and was itself in the form of an expression.
  • A feature of early Lisp systems was the use of dynamic scoping

COMMON LISP

·         A combination of several dialects of Lisp

·         The list of features of COMMON Lisp are:

o        A large number of data types and structures, including such things as records, arrays, complex numbers, and character strings

o        Powerful input and output operations

o        A form of packages for modularizing collections of functions and data

o        Providing access control

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