1 files changed, 64 insertions, 23 deletions
diff --git a/txr.1 b/txr.1
index e36c220c..65e52bce 100644
--- a/txr.1
+++ b/txr.1
@@ -33913,43 +33913,84 @@ flanking elements obtained from
 
 If
 .meta boundary
-is the keyword
+argument is specified as the keyword
 .codn :wrap ,
-then the sequence is effectively flanked by copies of itself on both
-ends, repeated enough times to satisfy the window. For instance if
-the sequence is
+then the sequence is imagined to be flanked at either end by an infinite
+repetition of copies of itself. These flanks are trimmed to the window size to
+generate the boundary.
+
+For instance if the sequence is
 .code "(1 2 3)"
 and the window size is 9 due to the value of
 .meta range
-being 7, then the behavior of
+being 4, then the behavior of
 .code :wrap
-is as if a
+is as if
 .meta boundary
-were specified consisting of
-.codn "(3 1 2 3 1 2 3 1)" .
+value of
+.code "(3 1 2 3 1 2 3 1)"
+were specified.
 The left flank is
-.code "(3 1 2 3)"
-and the right flank is
-.code "(1 2 3 4)"
-formed by repetitions of
-.code "(1 2 3)"
-surrounding it on either side, extending out to infinity, and chopped to
-.metn range .
+.codn "(3 1 2 3)" ,
+being the last four elements of an infinite repetition of
+.codn "1 2 3" ;
+and the right flank is similarly
+.codn "(1 2 3 1)" ,
+being the first four elements of an infinite repetition of
+.codn "1 2 3" .
 
 If
 .meta boundary
-is the keyword
+is given as the keyword
 .codn :reflect ,
-then the sequence is effectively flanked by reversed copies of itself
-on both ends, repeated enough times to satisfy the window.
-For instance if the sequence is
+then the sequence is imagined to be flanked at either end by an infinite
+repetition of reversed copies of itself. These flanks are trimmed to the window
+size to generate the boundary. For instance if the sequence is
 .code "(1 2 3)"
-and the window size is 9, then the behavior of
+and the window size is 9 due to the value of
+.meta range
+being 4, then the behavior of
 .code :reflect
-is as if a
+is as if
 .meta boundary
-were specified consisting of
-.codn "(1 3 2 1 3 2 1 3)" .
+value of
+.code "(1 3 2 1 3 2 1 3)"
+were specified.
+The left flank is
+.codn "(1 3 2 1)" ,
+being the last four elements of an infinite repetition of
+.codn "3 2 1" ;
+and the right flank is similarly
+.codn "(3 2 1 3)" ,
+being the first four elements of an infinite repetition of
+.codn "3 2 1" .
+
+.TP* Examples:
+.verb
+  ;; change characters between angle brackets to upper case.
+  [window-map 1 nil (lambda (x y z)
+                      (if (and (eq x #\<)
+                               (eq z #\>))
+                        (chr-toupper y)
+                        y))
+              "ab<c>de<f>g"]
+  --> "ab<C>de<F>g"
+
+  ;; collect all numbers which are the centre element of
+  ;; a monotonically increasing triplet
+  [window-mappend 1 :reflect (lambda (x y z)
+                               (if (< x y z)
+                                 (list y)))
+                  '(1 2 1 3 4 2 1 9 7 5 7 8 5)]
+  --> (3 7)
+
+  ;; calculate a moving average with a five-element
+  ;; window, flanked by zeros at the boundaries:
+  [window-map 2 #(0 0 0 0)
+              (lambda (. args) (/ (sum args) 5))
+              #(4 7 9 13 5 1 6 11 10 3 8)]
+  --> #(4.0 6.6 7.6 7.0 6.8 7.2 6.6 6.2 7.6 6.4 4.2))
+.brev
 
 .coNP Function @ interpose
 .synb