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| -rw-r--r-- | kaakaa/utils.scm | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/kaakaa/utils.scm b/kaakaa/utils.scm index 5677af2..a922ef2 100644 --- a/kaakaa/utils.scm +++ b/kaakaa/utils.scm @@ -22,6 +22,7 @@ #:use-module (ice-9 match) #:use-module (ice-9 popen) #:export (-> + foldn alist->plist call-with-input-pipe)) @@ -43,6 +44,27 @@ For example: => 16" (->-helper x (cut proc ...) ...)) +(define (foldn proc lst . inits) + "Apply @var{proc} to the elements of @var{lst} to build a result, and return +that result. @var{proc} may return multiple values, in which case, an equal +number of values are returned. Each @var{proc} call is @code{(proc element +previous ...)} where @code{element} is an element of @var{lst}, and +@code{(previous ...)} is the return from the previous call to @var{proc} or the +given @var{inits} for the first call. For example, + +(foldn (lambda (n sum sum-of-squares) + (values (+ sum n) + (+ sum-of-squares (expt n 2)))) + (iota 10) + 0 0) +=> 45 +=> 285" + (apply values + (fold (lambda (element results) + (call-with-values (cut apply proc element results) list)) + inits + lst))) + (define (alist->plist alist) "Convert association list @var{alist} to a property list. Keys in @var{alist} are converted to keywords." |