4 files changed, 26 insertions(+), 2 deletions(-)

M ChangeLog
M DESCRIPTION
M NEWS
M R/neighbourfun.R

@@ 1,3 1,7 @@
+2021-09-01  Enrico Schumann  <es@enricoschumann.net>
+
+	* R/neighbourfun.R (ans): add type "permute"
+
 2020-06-05  Enrico Schumann  <es@enricoschumann.net>
 
         * R/neighbourfun.R (compare_vectors): simplify

@@ 2,7 2,7 @@ Package: neighbours
 Type: Package
 Title: Neighbourhood Functions for Local-Search Algorithms
 Version: 0.1-0
-Date: 2020-08-02
+Date: 2021-09-01
 Maintainer: Enrico Schumann <es@enricoschumann.net>
 Authors@R: person(given = "Enrico", family = "Schumann",
                   role  = c("aut", "cre"),

@@ 1,4 1,4 @@
-v0.1-0  (2020-??-??)
+v0.1-0  (2021-??-??)
 
   o Initial release.  The package provides a function
     neighbourfun() that constructs neighbourhood

@@ 118,6 118,26 @@ neighbourfun <- function(min = 0,
         return(ans)
     }
 
+    if (type == "permute") {
+
+        if (missing(stepsize) || stepsize == 1L)
+            stepsize <- 2L
+
+        if (stepsize == 2L) {
+            ans <- function(x, ...) {
+                ii <- sample.int(length(x), stepsize)
+                x[ii] <- x[ii[2:1]]
+                x
+            }
+        } else {
+            ans <- function(x, ...) {
+                ii <- sample.int(length(x), stepsize)
+                x[ii] <- x[sample.int(ii)]
+                x
+            }
+        }
+        return(ans)
+    }
 
     if (type == "logical") {