March 2014 update

Task/Loop-over-multiple-arrays-simultaneously/TXR/loop-over-multiple-arrays-simultaneously-2.txr

@@ -0,0 +1,4 @@
+$ txr -e '(pprint (mappend (op list) "abc" "ABC" "123" (repeat "\n"))))'
+aA1
+bB2
+cC3

Task/Loop-over-multiple-arrays-simultaneously/TXR/loop-over-multiple-arrays-simultaneously-3.txr

@@ -0,0 +1,4 @@
+$ txr -e '(each ((x "abc") (y "ABC") (z "123")) (put-line `@x@y@z`))'
+aA1
+bB2
+cC3

Task/Loop-over-multiple-arrays-simultaneously/TXR/loop-over-multiple-arrays-simultaneously-4.txr

@@ -0,0 +1,22 @@
+@(do
+   ;; Scheme's vector-for-each: a one-liner in TXR
+   ;; that happily works over strings and lists.
+   (defun vector-for-each (fun . vecs)
+     [apply mapcar fun (range) vecs])
+
+   (defun display (obj : (stream *stdout*))
+     (pprint obj stream))
+
+   (defun newline (: (stream *stdout*))
+     (display #\newline stream))
+
+   (let ((a (vec "a" "b" "c"))
+         (b (vec "A" "B" "C"))
+         (c (vec 1 2 3)))
+     (vector-for-each
+       (lambda (current-index i1 i2 i3)
+         (display i1)
+         (display i2)
+         (display i3)
+         (newline))
+       a b c)))

Task/Loop-over-multiple-arrays-simultaneously/TXR/loop-over-multiple-arrays-simultaneously-5.txr

@@ -0,0 +1,17 @@
+@(do
+   (macro-time
+     (defun question-var-to-meta-num (var)
+       ^(sys:var ,(int-str (cdr (symbol-name var))))))
+
+   (defmacro map (square-fun . square-args)
+     (tree-bind [(fun . args)] square-fun
+       ^[apply mapcar (op ,fun ,*[mapcar question-var-to-meta-num args])
+               (macrolet ([(. args) ^(quote ,args)])
+                  (list ,*square-args))]))
+
+   (defun word (. items)
+     [apply format nil "~a~a~a" items])
+
+   (defun show (x) (pprinl x))
+
+   (show (map [(word ?1 ?2 ?3)] [a b c] [A B C] [1 2 3])))