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Task/Stack/REBOL/stack.rebol

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+REBOL [
+	Title: "Stack"
+	Author: oofoe
+	Date: 2010-10-04
+	URL: http://rosettacode.org/wiki/Stack
+]
+
+stack: make object! [
+	data: copy []
+
+	push: func [x][append data x]
+	pop: func [/local x][x: last data  remove back tail data  x]
+	empty: does [empty? data]
+
+	peek: does [last data]
+]
+
+; Teeny Tiny Test Suite
+
+assert: func [code][print [either do code ["  ok"]["FAIL"]  mold code]]
+
+print "Simple integers:"
+s: make stack []  s/push 1  s/push 2 ; Initialize.
+
+assert [2 = s/peek]
+assert [2 = s/pop]
+assert [1 = s/pop]
+assert [s/empty]
+
+print [lf "Symbolic data on stack:"]
+v: make stack [data: [this is a test]] ; Initialize on instance.
+
+assert ['test = v/peek]
+assert ['test = v/pop]
+assert ['a = v/pop]
+assert [not v/empty]