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McCarthy's pure Lisp existed only on paper. The first Lisp that ran on a computer had mutable variables, as did Lisp 1.5, Maclisp, etc... Immutability require

• agumonkey 3mo ago
  fair point but from memory most of early programs in his paper were purely immutable in nature (tree recursion and substition), right ?
  • dismalaf 3mo ago
    Yes but he also wrote this when describing the language: > In addition to the facilities for describing S-functions, there are facilities for using S-functions in programs written as sequences of statements along the lines of FORTRAN (4) or ALGOL (5). These features will not be described in this article
    • agumonkey 3mo ago
      hmm funny i completely missed that, i thought these traits were introduced a bit later