Editing Talk:312: With Apologies to Robert Frost

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:To what degree is the rigidity of matching parentheses a feature of Lisp and not a feature of specific implementations of it? I remember one of my professors telling me that they used to just throw a bunch of parentheses at the end of the program. I know in at least one implementation, there is at least a variable that, when true, causes the interpreter to ignore extra right parentheses. As for Perl, if you wish to add more information to the explanation about it, then I'd say go ahead. However, at present there's not really any comparison between the two languages at all in the text. I didn't feel that it was especially necessary to understand the details of Perl to get the comic, so I didn't describe it beyond calling it a popular computer programming language. [[User:Erenan|Erenan]] ([[User talk:Erenan|talk]]) 12:03, 1 August 2012 (EDT)
 
:To what degree is the rigidity of matching parentheses a feature of Lisp and not a feature of specific implementations of it? I remember one of my professors telling me that they used to just throw a bunch of parentheses at the end of the program. I know in at least one implementation, there is at least a variable that, when true, causes the interpreter to ignore extra right parentheses. As for Perl, if you wish to add more information to the explanation about it, then I'd say go ahead. However, at present there's not really any comparison between the two languages at all in the text. I didn't feel that it was especially necessary to understand the details of Perl to get the comic, so I didn't describe it beyond calling it a popular computer programming language. [[User:Erenan|Erenan]] ([[User talk:Erenan|talk]]) 12:03, 1 August 2012 (EDT)
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::Almost all implementations of Lisp require exact parenthesis matching.  The Common Lisp spec requires the reader to issue an error if there's an unmatched right paren.  The Scheme spec is less demanding about making the implementation report such errors, but a standards-conforming program still needs matched parens.  There are a few exceptions, though.  Several Schemes let you use "()", "[]", or "{}" as delimiters.  But other than your note about Lispwork's *ignore-extra-right-parens*, I only know of one that deliberately lets you have mismatched parens: Interlisp lets you use "]" to match all the pending open parentheses, up to the most recent "[".  So, for instance, you could write "(let [(there (be light])", and the "]" would act like "))".  (Genera may have adopted this too; I don't remember offhand.)  This didn't seem to take off, though (I suspect comic #859 is relevant).  Most Lispers I know just use slime-repl-closing-return (C-RET in the REPL) or slime-close-all-parens-in-sexp (C-c C-] in a Lisp buffer).  [[User:Piquan|Piquan]] ([[User talk:Piquan|talk]]) 02:45, 11 February 2018 (UTC)
 
  
 
Lisp rhymes with myth and with, but only if you have a lithp. Think he did that on purpose?
 
Lisp rhymes with myth and with, but only if you have a lithp. Think he did that on purpose?

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