Sharp Quote

#' is a frequently-used ReadMacro in CommonLisp. ("Sharp quote" because # means 'sharp' in MusicalNotation? and ' is the QuoteOperator? in Lisp.)

 #'foo

expands to (is SyntacticSugar for)

 (function foo)

Every symbol in CommonLisp can refer to both a function and a value. Since

 foo

by itself refers to the value, we write

 (function foo)

to refer to the function. The function special form is also used to create a LexicalClosure from a LambdaExpression. (A lambda expression may also be executed directly, but this actually macro-expands to the (function (lambda ... )) form.

In essence, all this means that function is a special form such that (funcall (function <whatever>) ...) evaluates to (<whatever> ...).

See SingleNamespaceLisp, FunctionLambda.

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CategoryCommonLisp