1 Here are the definitions pre-loaded for working on assignment 3:
3 <textarea id="INPUT" style="border: 2px solid black; color: black; font-family: monospace; height: 3in; overflow: auto; padding: 0.5em; width: 100%;">
7 let and = \l r. l (r true false) false in
8 let make_pair = \f s g. g f s in
11 let empty = make_pair true junk in
12 let isempty = \x. x fst in
13 let make_list = \h t. make_pair false (make_pair h t) in
14 let head = \l. isempty l err (l snd fst) in
15 let tail = \l. isempty l err (l snd snd) in
17 ; a list of numbers to experiment on
18 let mylist = make_list 1 (make_list 2 (make_list 3 empty)) in
21 let iszero = \n. n (\x. false) true in
22 let succ = \n s z. s (n s z) in
23 let mul = \m n s. m (n s) in
24 let pred = \n. iszero n 0 (length (tail (n (\p. make_list junk p) empty))) in
25 let leq = \m n. iszero(n pred m) in
26 let eq = \m n. and (leq m n)(leq n m) in
28 ; a fixed-point combinator for defining recursive functions
29 let Y = \f. (\h. f (h h)) (\h. f (h h)) in
31 let length = Y (\length l. isempty l 0 (succ (length (tail l)))) in
34 let makePair = make_pair in
36 let isNil = isempty in
37 let makeList = make_list in
38 let isZero = iszero in
44 <input id="PARSE" value="Normalize" type="button">
45 <input id="ETA" type="checkbox">do eta-reductions too
46 <noscript><p>You may not see it because you have JavaScript turned off. Uffff!</p></noscript>
47 <script src="/code/lambda.js"></script>
48 <script src="/code/tokens.js"></script>
49 <script src="/code/parse.js"></script>
50 <script src="/code/json2.js"></script>
54 /*jslint evil: true */
56 /*members create, error, message, name, prototype, stringify, toSource,
60 /*global JSON, make_parse, parse, source, tree */
62 // Make a new object that inherits members from an existing object.
64 if (typeof Object.create !== 'function') {
65 Object.create = function (o) {
72 // Transform a token object into an exception object and throw it.
74 Object.prototype.error = function (message, t) {
76 t.name = "SyntaxError";
83 var parse = make_parse();
86 var string, tree, expr, eta;
89 // string = JSON.stringify(tree, ['key', 'name', 'message', 'value', 'arity', 'first', 'second', 'third', 'fourth'], 4);
90 expr = tree.handler();
91 // string = JSON.stringify(expr, ['key', 'name', 'message', 'value', 'arity', 'first', 'second', 'tag', 'variable', 'left', 'right', 'bound', 'body' ], 4);
92 // string = expr.to_string() + "\n\n~~>\n\n";
94 eta = document.getElementById('ETA').checked;
95 string = string + reduce(expr, eta, false).to_string();
97 string = JSON.stringify(e, ['name', 'message', 'from', 'to', 'key',
98 'value', 'arity', 'first', 'second', 'third', 'fourth'], 4);
100 document.getElementById('OUTPUT').innerHTML = string
101 .replace(/&/g, '&')
102 .replace(/[<]/g, '<');
105 document.getElementById('PARSE').onclick = function (e) {
106 go(document.getElementById('INPUT').value);