Created
March 2, 2012 13:54
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Option, which you may know as 'Maybe'.
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| function write(message) { | |
| document.getElementById("output").innerHTML += message + "<br />"; | |
| } | |
| function assertEquals(expected, actual) { | |
| if (expected === actual) { | |
| write("OK"); | |
| } else { | |
| var text = "expected = [" + expected.toString() | |
| + "], but actual = [" + actual.toString() + "]." | |
| write("Failure: " + text); | |
| } | |
| } | |
| function assertTrue(target) {assertEquals(true, target);} | |
| function assertFalse(target) {assertEquals(false, target);} |
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| document.write('<script type="text/javascript" src="myJsUnit.js"></script>'); | |
| function Option(){}; | |
| Option.prototype = { | |
| isSome : function(){}, | |
| bind : function(f) {} | |
| }; | |
| function Some(value) { | |
| Option.call(this); | |
| this.value = value; | |
| } | |
| Some.prototype = new Option(); | |
| Some.prototype.isSome = function() { return true; }; | |
| Some.prototype.bind = function(f) { return f(this.value); }; | |
| function None() { | |
| Option.call(this); | |
| } | |
| None.prototype = new Option(); | |
| None.prototype.isSome = function() { return false; }; | |
| None.prototype.bind = function(f) { return this; }; | |
| function option(x) { | |
| if (x < 0) { | |
| return new None(); | |
| } else { | |
| return new Some(x); | |
| } | |
| } | |
| function tryAdd(x, y) { | |
| return option(x).bind(function(a){ | |
| return option(y).bind(function(b){ | |
| return option(a+b) | |
| }) | |
| }); | |
| } | |
| function testSuite() { | |
| var some3 = tryAdd(1, 2); | |
| assertTrue(some3.isSome()); | |
| assertEquals(3, some3.value); | |
| var none = tryAdd(4, -1); | |
| assertFalse(none.isSome());} | |
| window.onload = testSuite; |
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <title>Option test</title> | |
| <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> | |
| <script type="text/javascript" src="option.js"></script> | |
| </head> | |
| <body> | |
| <div id="output" /> | |
| </body> | |
| </html> |
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