Backquote and Comma Syntax

Allows the body of a macro to look like the expanded form.

(defmacro push (element stack)

‘(if (null ,stack) (setq ',stack '(,element))

(setq ,stack (cons ,element ,stack)) ) )

>(macroexpand '(push 5 s))

(IF (NULL S)(SETQ 'S '(5))(SETQ S (CONS 5 S)))

T

Backquote is like QUOTE but it allows subexpressions preceded by a comma to be evaluated.

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