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post: Add posts/group-by-tag. 

* haunt/post.scm (group-by-tag): New procedure.
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David Thompson 2015-04-11 23:34:23 -04:00
parent 390980cf5c
commit 44fdd16202
1 changed files with 15 additions and 0 deletions
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15
haunt/post.scm
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@ -23,6 +23,7 @@
;;; Code: ;;; Code:
(define-module (haunt post) (define-module (haunt post)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-9) #:use-module (srfi srfi-9)
#:use-module (srfi srfi-19) #:use-module (srfi srfi-19)
#:use-module (haunt utils) #:use-module (haunt utils)
@ -34,6 +35,7 @@
post-ref post-ref
post-slug post-slug
posts/reverse-chronological posts/reverse-chronological
posts/group-by-tag
register-metdata-parser! register-metdata-parser!
parse-metadata)) parse-metadata))
@ -66,6 +68,19 @@
(lambda (a b) (lambda (a b)
(time>? (post->time a) (post->time b))))) (time>? (post->time a) (post->time b)))))
(define (posts/group-by-tag posts)
"Return an alist of tags mapped to the posts that used them."
(let ((table (make-hash-table)))
(for-each (lambda (post)
(for-each (lambda (tag)
(let ((current (hash-ref table tag)))
(if current
(hash-set! table tag (cons post current))
(hash-set! table tag (list post)))))
(or (post-ref post 'tags) '())))
posts)
(hash-fold alist-cons '() table)))
;;; ;;;
;;; Metadata ;;; Metadata
;;; ;;;