Nikodemus Siivola

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Neat TYPEP Trick #
hacking, May 15th 2012

How do you test if an object is a cons that has the desired symbol in the car?

(typep x '(cons (eql :foo)))


(and (consp x) (eq :foo (car x)))

is essentially just as short...

I still find cons types neat, even if they're a nightmare when it comes to type derivation, but that's a different matter. Some nightmares aren't all bad.