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comp.lang.lisp

Re: Anaphoric macros and packages

William James

7/23/2015 8:51:00 PM

Erik Naggum wrote:

> (whereas ((expr-1 (whatever-1))
> (expr-2 (whatever-2)))
> (something-using-expr-1-and/or-expr-2))
>
> Reading it like the standard contract legalese, the key idea is that all
> prior forms are true when an expression in the binding forms is evaluated
> (just like the operator `and') and prior variable are bound to the (true)
> value of each prior expression. The body is an implicit `progn' that can
> thus rely on all of these forms having non-nil values.

Gauche Scheme:

(and-let* ((a (assoc 'bar '((foo . 33) (bar . 44))))
(b (cdr a)))
b)
===>
44

(and-let* ((a (assoc 'who '((foo . 33) (bar . 44))))
(b (cdr a)))
b)
===>
#f

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