I'm a little new to Emacs. When looking at some of the configurations, I found there are two types command in "add-hook".

(add-hook 'LaTeX-mode-hook #'LaTeX-math-mode)


(add-hook 'LaTeX-mode-hook 'LaTeX-math-mode)

This has confused me for a long time and I don't know how to search "#'" in google...



1 Answer 1


In Emacs Lisp, if foo is a symbol, then 'foo and #'foo are completely equivalent. The latter form (with #') is preferred when foo is a function, as it documents the fact that it is intended to be funcalled.

Your two forms are therefore completely equivalent, and the one with #' is preferred.

Edit: as pointed out by Malabarba, this is not quite true: #' on symbols will cause the byte-compiler to emit a warning if the function is not defined.

(Note that this is not the case for lambda-forms, for which plain ' prevents the byte-compiler from compiling the lambda-form, as documented elsewhere. Note further that this is also not necessarily the case in other Lisp dialects, for example in Common Lisp #'foo performs early binding.)


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