Initial data commit

Task/Stack/Jq/stack-1.jq

@@ -0,0 +1,20 @@
+# create a Stack
+def Stack: {stack: []};
+
+# check an object is a Stack
+def isStack:
+  type == "object" and has("stack") and (.stack|type) == "array";
+
+def pop:
+  if .stack|length == 0 then "pop: stack is empty" | error
+  else {stack: .stack[1:], item: .stack[0]]
+  end;
+
+def push($x):
+  .stack = [$x] + .stack | .item = null;
+
+def size:
+  .stack | length;
+
+def isEmpty:
+  size == 0;