Data commit

Task/Permutations/Langur/permutations.langur

@@ -0,0 +1,39 @@
+val .factorial = f if(.x < 2: 1; .x x self(.x - 1))
+
+val .permute = f(.arr) {
+    if not isArray(.arr): throw "expected array"
+
+    val .limit = 10
+    if len(.arr) > .limit: throw $"permutation limit exceeded (currently \.limit;)"
+
+    var .elements = .arr
+    var .ordinals = pseries len .elements
+
+    val .n = len(.ordinals)
+    var .i, .j
+
+    for[.p=[.arr]] of .factorial(len .arr)-1 {
+        .i = .n - 1
+        .j = .n
+        while .ordinals[.i] > .ordinals[.i+1] {
+            .i -= 1
+        }
+        while .ordinals[.j] < .ordinals[.i] {
+            .j -= 1
+        }
+
+        .ordinals[.i], .ordinals[.j] = .ordinals[.j], .ordinals[.i]
+        .elements[.i], .elements[.j] = .elements[.j], .elements[.i]
+
+        .i += 1
+        for .j = .n; .i < .j ; .i, .j = .i+1, .j-1 {
+            .ordinals[.i], .ordinals[.j] = .ordinals[.j], .ordinals[.i]
+            .elements[.i], .elements[.j] = .elements[.j], .elements[.i]
+        }
+        .p = more .p, .elements
+    }
+}
+
+for .e in .permute([1, 3.14, 7]) {
+    writeln .e
+}