### Lecture on Newlisp, 6. June 2010.

 I'll give a public lecture on Newlisp at Sunday evening, 6. June 2010, 18:00, Hacklab Mama, Preradovićeva 18, Zagreb. The organizer is LangGang, regional alternative languages interest group, and Alan Pavičić. All interested readers are welcome. UPDATE: That's me, talking about  crawler-tractor . I was told that lecture was interesting, and we ended that meeting in local pizzeria. Thanks to all visitors. If you're programmer from Zagreb or passing through, and you're interested in such kind of lectures and socialization, take a look at official webpage. Here is short movie recorded during one previous, unrelated event in Hacklab, so you can see the atmosphere.

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### Short notes on McCarthy's "Recursive Functions ... "

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If you like the notes, but you prefer white background

check here

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### Interesting Case of Mismatched Parentheses.

 * Programming language: Lisp. One of the most important programming     languages, and probably the most important if we discuss parentheses.        * Author: John McCarthy, the creator of Lisp.   * Article: Recursive Functions of Symbolic Expressions, Communications     of the ACM, April 1960, probably the most important article on Lisp.        * Place: definition of arguably the most important function ever: eval. The holiest place for programmers not afraid of parentheses!

Yet, parentheses do not match there.

 This is not typical Lisp S-expression, it is so called "meta expression". Here is original version of the article:

 And here is the same mismatch in the version retyped using Latex.

 I'll not say where is the error. I'll leave you to play with that. Here is the text, so you can copy and paste it in your editor. The simplest way to check my claim that there is an error is that your editor counts left and right brackets. Notepad++ says there are 68 left and 66 right brackets here.

 eval[e; a] = [ atom [e] -> assoc [e; a]; atom [car [e]] -> [ eq [car [e]; QUOTE] -> cadr [e]; eq [car [e]; ATOM] -> atom [eval [cadr [e]; a]]; eq [car [e]; EQ] -> [eval [cadr [e]; a] = eval [caddr [e]; a]]; eq [car [e]; COND] -> evcon [cdr [e]; a]; eq [car [e]; CAR] -> car [eval [cadr [e]; a]]; eq [car [e]; CDR] -> cdr [eval [cadr [e]; a]]; eq [car [e]; CONS] -> cons [eval [cadr [e]; a]; eval [caddr [e];              a]]; T -> eval [cons [assoc [car [e]; a];                                           evlis [cdr [e]; a]]; a]]; eq [caar [e]; LABEL] -> eval [cons [caddar [e]; cdr [e]];                         cons [list [cadar [e]; car [e]; a]]; eq [caar [e]; LAMBDA] -> eval [caddar [e];                              append [pair [cadar [e]; evlis [cdr [e]; a]; a]]]

 Some puritans might insist that it is brackets mismatch and not parentheses mismatch. Wikipedia thinks that brackets are one type of parentheses. Of course, I cannot say that it is one of the most important parentheses mismatches in history of programming. It had no effect whatsoever, as far as I know. Herbert Stoyan wrote about this error, and it is mentioned in Latex version of the McCarthy's article, 1995. Similar error in Lisp I. Programmer's Manual. It is brought to my attention that intern unofficial publication, "LISP I. Programmer's manual" from March 1960, has different definition:

 However, it is also likely wrong. Look at the line with LABEL, and two occurrences of cdr[e]. With some help of Shubert who commented this post, I believe that the it should be:

 ```eval[e; a] = [ atom [e] -> assoc [e; a]; atom [car [e]] -> [ eq [car [e]; QUOTE] -> cadr [e]; eq [car [e]; ATOM] -> atom [eval [cadr [e]; a]]; eq [car [e]; EQ] -> [eval [cadr [e]; a] = eval [caddr [e]; a]]; eq [car [e]; COND] -> evcon [cdr [e]; a]; eq [car [e]; CAR] -> car [eval [cadr [e]; a]]; eq [car [e]; CDR] -> cdr [eval [cadr [e]; a]]; eq [car [e]; CONS] -> cons [eval [cadr [e]; a]; eval [caddr [e]; a]]; T -> eval [cons [assoc [car [e]; a]; evlis [cdr [e]; a]]; a] ]; eq [caar [e]; LABEL] -> eval [ cons [caddar [e]; cdr [e]]; cons [list [cadar [e]; car [e]]; a] ]; eq [caar [e]; LAMBDA] -> eval [caddar [e]; append [pair [cadar [e]; evlis [cdr [e]; a] ]; a ] ] ] ```

Similar error in Memo 8.
 It is very interesting that error existed also in the third document, memo of AI project on MIT, 1959, which contains different definition of eval:

 For tried and tested EVAL see my post McCarthy's Lisp in Newlisp.

See also Mark Stock's link in comments of this post.

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