LabLISP Guide

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**''BACKQUOTE''**

Backquote expects one argument, typically a list, and can be also invoked with the backquote special character ''`''. In the example for quote form, the backquote form works the same:

<code lisp>
`(a b c)             ; backquote here is ..
(backquote (a b c))  ; .. same as quote
</code> 

But in backquoted list, some parts can be switched back to evaluation with comma character (see ''UNQUOTE''):

<code lisp>
>`(a ,(+ 1 2) c)    ; backquoted list
(A 3 C)             ; form (+ 1 2) evaluated
</code> 

While with normal quote we would have this:

<code lisp>
>'(a ,(+ 1 2) c)         ; quoted list
(A (UNQUOTE (+ 1 2)) C)  ; comma character expanded, but not evaluated
</code> 

And multiple backqoutes are ignored:

<code lisp>
>``(a ,(+ 1 2) c)   ; multiple backquoting ..
(A 3 C)             ; .. behaves as single backquote
</code> 

The forms ''BACKQUOTE'', ''UNQUOTE'' and ''SPLICE-UNQUOTE'' are useful for writing macros.