Revision as of 13:51, 5 January 2025 edit Skyvine (talk \| contribs) 278 edits m Update section target to existing section. Fixes one of the broken anchors listings in the template on the talk page. ← Previous edit		Revision as of 13:57, 5 January 2025 edit undo Skyvine (talk \| contribs) 278 edits m →Self-evaluating forms and quoting: The page on Grave accent was split, with the Backtick page discussing the stand-alone character. Update the link and the language here to align with that work. Fixes the other "broken anchor" listing in the talk page. Next edit →
Line 364: Any expression can also be marked to prevent it from being evaluated (as is necessary for symbols and lists). This is the role of the {{Lisp2\|quote}} special operator, or its abbreviation {{Lisp2\|'}} (one quotation mark). For instance, usually if entering the symbol {{Lisp2\|foo}}, it returns the value of the corresponding variable (or an error, if there is no such variable). To refer to the literal symbol, enter {{Lisp2\|(quote foo)}} or, usually, {{Lisp2\|'foo}}. {{anchor\|Backquote}}Both Common Lisp and Scheme also support the ''backquote'' operator (termed ''[[quasiquote]]'' in Scheme), entered with the {{Lisp2\|`}} character ([[~~Grave accent#Use in programming\|grave accent~~Backtick]]). This is almost the same as the plain quote, except it allows expressions to be evaluated and their values interpolated into a quoted list with the comma {{Lisp2\|,}} ''unquote'' and comma-at {{Lisp2\|,@}} ''splice'' operators. If the variable {{Lisp2\|snue}} has the value {{Lisp2\|(bar baz)}} then {{Lisp2\|`(foo ,snue)}} evaluates to {{Lisp2\|(foo (bar baz))}}, while {{Lisp2\|`(foo ,@snue)}} evaluates to {{Lisp2\|(foo bar baz)}}. The backquote is most often used in defining macro expansions.<ref name="cTQAG">{{cite web\|url=http://www.cs.washington.edu/education/courses/cse341/04wi/lectures/14-scheme-quote.html \|title=CSE 341: Scheme: Quote, Quasiquote, and Metaprogramming \|publisher=Cs.washington.edu \|date=1999-02-22 \|access-date=2013-11-15}}</ref><ref name="waVLs">[http://repository.readscheme.org/ftp/papers/pepm99/bawden.pdf Quasiquotation in Lisp] {{Webarchive\|url=https://web.archive.org/web/20130603114956/http://repository.readscheme.org/ftp/papers/pepm99/bawden.pdf \|date=2013-06-03}}, Alan Bawden</ref> Self-evaluating forms and quoted forms are Lisp's equivalent of literals. It may be possible to modify the values of (mutable) literals in program code. For instance, if a function returns a quoted form, and the code that calls the function modifies the form, this may alter the behavior of the function on subsequent invocations.

Lisp (programming language): Difference between revisions