Created
December 11, 2011 11:16
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(library (tagbody utils) | |
(export plist->alist | |
shift-left | |
unzip | |
syntax->list | |
) | |
(import (rnrs)) | |
(define (syntax->list stxobj) | |
(define (inner stx) | |
(syntax-case stx () | |
[() '()] | |
[(x . rest) | |
(cons #'x (inner #'rest))])) | |
(assert (list? (syntax->datum stxobj))) | |
(inner stxobj)) | |
(define (plist->alist car? plist) | |
;; assumes head of (car? plist) is true | |
(define (rcons a b) | |
(cons (reverse a) b)) | |
(if (null? plist) | |
'() | |
(let loop ((plist (cdr plist)) | |
(current-field (list (car plist))) | |
(return-list '())) | |
(cond ((null? plist) | |
(reverse | |
(if (null? current-field) | |
return-list | |
(rcons current-field return-list)))) | |
((car? (car plist)) | |
(loop (cdr plist) | |
(list (car plist)) | |
(rcons current-field return-list))) | |
(else | |
(loop (cdr plist) | |
(cons (car plist) current-field) | |
return-list)))))) | |
(define (unzip list-of-pairs) | |
(let loop ((pairs list-of-pairs) (cars '()) (cdrs '())) | |
(if (null? pairs) | |
(values (reverse cars) (reverse cdrs)) | |
(loop (cdr pairs) (cons (caar pairs) cars) | |
(cons (cdar pairs) cdrs))))) | |
(define (shift-left old-list end) | |
(append (cdr old-list) (list end))) | |
) |
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