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From: "B. Pym" <Nobody447095@here-nor-there.org>
Newsgroups: comp.lang.lisp,comp.lang.scheme
Subject: Re: Simple problem in PG's ANSI Common Lisp
Date: Thu, 26 Sep 2024 02:17:26 -0000 (UTC)
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paul graham wrote:

> Or you could write
> 
> (defun pos+ (lst)
>   (let ((i -1))
>     (mapcar #'(lambda (x) (+ x (incf i)))
>             lst)))
> 
> Btw, in Arc that would be
> 
> (def pos+ (lst)
>   (let i -1
>     (map [+ _ (++ i)] lst)))


Gauche Scheme

(define (pos+ lst)
  (let1 i -1
    (map (~>  (+ (inc! i))) lst)))

Given:

(define-syntax ->
  (syntax-rules ()
    [(_ x)  x]
    [(_ x (y more ...) z ...)
     (-> (y x more ...) z ...)]
    [(_ x y z ...)
     (-> (y x) z ...)]))

(define-syntax ~>
  (syntax-rules ()
    [(_ (func0 a ...) func ...)
     (lambda xs (-> (apply func0 (append xs (list a ...))) func ...))]
    [(_ func0 func ...)
     (lambda xs (-> (apply func0 xs) func ...))]))