Common-Lisp and Emacs-Lisp identifiers can start with digits, e.g., 2pi, !, { and } are all valid identifiers. ?, [ and ] are valid identifiers in Common-Lisp. Emacs-Lisp identifiers cannot start with ? and cannot contain [ or ]. The rare, seldom seen #?, #!, #[, #], #{ and #} reader macros reserved for Common-Lisp users are far too obscure to mention.
Given that the https://hyperpolyglot.org/lisp.htmlidentifier info is at least half false,
it might be wise to check the other entries as well.
http://www.lispworks.com/documentation/lw50/CLHS/Body/02_cd.htm
2.3.4 Symbols as Tokens
Any token that is not a potential number, does not contain a package marker, and does not consist entirely of dots will always be interpreted as a symbol.
2.3.1.1 Potential Numbers as Tokens
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Common-Lisp and Emacs-Lisp identifiers can start with digits, e.g., 2pi, !, { and } are all valid identifiers. ?, [ and ] are valid identifiers in Common-Lisp. Emacs-Lisp identifiers cannot start with ? and cannot contain [ or ]. The rare, seldom seen #?, #!, #[, #], #{ and #} reader macros reserved for Common-Lisp users are far too obscure to mention. Given that the https://hyperpolyglot.org/lisp.html identifier info is at least half false, it might be wise to check the other entries as well. http://www.lispworks.com/documentation/lw50/CLHS/Body/02_cd.htm 2.3.4 Symbols as Tokens Any token that is not a potential number, does not contain a package marker, and does not consist entirely of dots will always be interpreted as a symbol. 2.3.1.1 Potential Numbers as Tokens …