Data commit

Task/Stack/UNIX-Shell/stack-1.sh

@@ -0,0 +1,33 @@
+init() {
+  if [[ -n $KSH_VERSION ]]; then
+    set -A stack
+  else
+    stack=(); # this sets stack to '()' in ksh
+  fi
+}
+
+push() {
+  stack=("$1" "${stack[@]}")
+}
+
+stack_top() {
+  # this approach sidesteps zsh indexing difference
+  set -- "${stack[@]}"
+  printf '%s\n' "$1"
+}
+
+pop() {
+  stack_top
+  stack=("${stack[@]:1}")
+}
+
+empty() {
+  (( ${#stack[@]} == 0 ))
+}
+
+# Demo
+push fred; push wilma; push betty; push barney
+printf 'peek(stack)==%s\n' "$(stack_top)"
+while ! empty; do
+  pop
+done