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Add a utility to group list values

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This is useful for some queries with duplicated parts of the results.
This commit is contained in:
Christopher Baines 2019-05-18 12:34:37 +01:00
parent 48070e4a99
commit 5124fbc471
1 changed files with 16 additions and 1 deletions
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17
guix-data-service/model/utils.scm
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@ -1,12 +1,14 @@
(define-module (guix-data-service model utils) (define-module (guix-data-service model utils)
#:use-module (srfi srfi-1) #:use-module (srfi srfi-1)
#:use-module (ice-9 vlist) #:use-module (ice-9 vlist)
#:use-module (ice-9 receive)
#:use-module (squee) #:use-module (squee)
#:export (quote-string #:export (quote-string
value->quoted-string-or-null value->quoted-string-or-null
exec-query->vhash exec-query->vhash
two-lists->vhash two-lists->vhash
deduplicate-strings)) deduplicate-strings
group-list-by-first-n-fields))
(define (quote-string s) (define (quote-string s)
(string-append "'" s "'")) (string-append "'" s "'"))
@ -41,3 +43,16 @@
(cons (first pair) result)))) (cons (first pair) result))))
'() '()
(sort strings string<?))) (sort strings string<?)))
(define (group-list-by-first-n-fields n lists)
(fold (lambda (lst groups)
(receive (key vals)
(split-at lst n)
(append
(alist-delete key groups)
`((,key . ,(append
(or (assoc-ref groups key)
'())
(list vals)))))))
'()
lists))