deque-empty? ( deque -- ? )
Persistent deques

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Vocabulary
persistent.deques

Inputs

deque

a deque

Outputs

?

t/f

Word description
Returns true if the deque is empty. This takes constant time.

Definition

USING: accessors combinators.short-circuit lists ;

IN: persistent.deques

: deque-empty? ( deque -- ? )
    { [ front>> nil? ] [ back>> nil? ] } 1&& ;