3 files changed, 38 insertions(+), 0 deletions(-)

M algorithms.scm
M doc/algorithms.texi
M tests/test-algorithms.scm

@@ 16,6 16,7 @@
             generate
             increasing?
             init
+            juxt
             product
             repeat
             replicate


@@ 56,6 57,10 @@
 (define (init lst)
   (drop-right lst 1))
 
+(define (juxt . procs)
+  (λ args
+    (map (λ (proc) (apply proc args)) procs)))
+
 (define (product lst)
   (fold-right * 1 lst))
 

@@ 192,6 192,28 @@ Examples:
 @end example
 @end deffn
 
+@deffn {Scheme Procedure} juxt @var{proc}@dots{}
+Takes variable number of procedures and returns a procedure that is the juxtaposition
+of those procedures.  The returned procedure takes a variable number of arguments, and
+returns a list containing the result of applying each procedures to the
+arguments.
+
+This algorithm comes from Clojure's
+@code{@url{https://clojuredocs.org/clojure.core/juxt, juxt}}.
+
+Examples:
+@example
+> ((juxt first last) '(1 2 3))
+'(1 3)
+> ((juxt + *) 1 2 3 4)
+'(10 24)
+> ((juxt zip append)  '(1 2 3) '(4 5 6))
+'(((1 4) (2 5) (3 6)) (1 2 3 4 5 6))
+@end example
+@end deffn
+
+
+
 @deffn {Scheme Procedure} product @var{lst}
 Returns the product of the elements in @var{lst}.
 

@@ 1,5 1,9 @@
 (define-module (test-algoritms)
+  #:use-module ((srfi srfi-1) #:select (first
+                                        last
+                                        zip))
   #:use-module (srfi srfi-64)
+
   #:use-module (algorithms))
 
 (module-define! (resolve-module '(srfi srfi-64))


@@ 79,6 83,13 @@
   (test-equal '()
     (init '(1)))
 
+  (test-equal '(5 6)
+    ((juxt + *) 2 3))
+  (test-equal '(1 3)
+    ((juxt first last) '(1 2 3)))
+  (test-equal '(((1 4) (2 5) (3 6)) (1 2 3 4 5 6))
+    ((juxt zip append)  '(1 2 3) '(4 5 6)))
+
   (test-equal 6
     (product '(3 2 1)))
   (test-equal 3628800