A-M baby

Task/Search-a-list/GAP/search-a-list.gap

@@ -0,0 +1,27 @@
+# First position is built-in
+haystack := Eratosthenes(10000);;
+needle := 8999;;
+Position(haystack, needle);
+# 1117
+
+LastPosition := function(L, x)
+  local old, new;
+  old := 0;
+  new := 0;
+  while new <> fail do
+    new := Position(L, x, old);
+    if new <> fail then
+      old := new;
+    fi;
+  od;
+  return old;
+end;
+
+a := Shuffle(List([1 .. 100], x -> x mod 10));
+# [ 0, 2, 4, 5, 3, 1, 0, 4, 8, 8, 2, 7, 6, 3, 3, 6, 4, 4, 3, 0, 7, 1, 8, 7, 2, 4, 7, 9, 4, 9, 4, 5, 9, 9, 6, 7, 8, 2, 3,
+#   5, 1, 5, 4, 2, 0, 9, 6, 1, 1, 2, 2, 0, 5, 7, 6, 8, 8, 3, 1, 9, 5, 1, 9, 6, 8, 9, 2, 0, 6, 2, 1, 6, 1, 1, 2, 5, 3, 3,
+#   0, 3, 5, 7, 5, 4, 6, 8, 0, 9, 8, 3, 7, 8, 0, 4, 9, 7, 0, 6, 5, 7 ]
+Position(a, 0);
+# 1
+LastPosition(a, 0);
+# 97