@@ -139,6 +139,9 @@ (define-module (guix utils)
with-environment-variables
arguments-from-environment-variable
+ flatten
+ flat-map
+
config-directory
cache-directory
@@ -1028,6 +1031,29 @@ (define (with-atomic-file-output file proc)
(false-if-exception (delete-file template))
(close-port out)))))
+;; TODO: bring over other utility procedures from (haunt utils).
+(define* (flatten lst #:optional depth)
+ "Return a list that recursively concatenates the sub-lists of LST,
+up to DEPTH levels deep. When DEPTH is #f, the entire tree is
+flattened."
+ (if (and (number? depth) (zero? depth))
+ lst
+ (fold-right (match-lambda*
+ (((sub-list ...) memo)
+ (append (flatten sub-list (and depth (1- depth)))
+ memo))
+ ((elem memo)
+ (cons elem memo)))
+ '()
+ lst)))
+
+(define (flat-map proc . lsts)
+ "Apply PROC to each element of each list in LSTS and return a new
+list in which nested lists are concatenated into the result.
+
+For example, the list (1 2 (3)) would be flattened to (1 2 3)."
+ (flatten (apply map proc lsts) 1))
+
(define* (xdg-directory variable suffix #:key (ensure? #t))
"Return the name of the XDG directory that matches VARIABLE and SUFFIX,
after making sure that it exists if ENSURE? is true. VARIABLE is an