+++ /dev/null
-Here are the definitions pre-loaded for working on assignment 3:
-
-<textarea id="INPUT" style="border: 2px solid black; color: black; font-family: monospace; height: 3in; overflow: auto; padding: 0.5em; width: 100%;">
- ; booleans
- let true = \x y. x in
- let false = \x y. y in
- let and = \l r. l (r true false) false in
- let make_pair = \f s g. g f s in
- let fst = true in
- let snd = false in
- let empty = make_pair true junk in
- let isempty = \x. x fst in
- let make_list = \h t. make_pair false (make_pair h t) in
- let head = \l. isempty l err (l snd fst) in
- let tail = \l. isempty l err (l snd snd) in
-
- ; a list of numbers to experiment on
- let mylist = make_list 1 (make_list 2 (make_list 3 empty)) in
-
- ; church numerals
- let iszero = \n. n (\x. false) true in
- let succ = \n s z. s (n s z) in
- let mul = \m n s. m (n s) in
- let pred = \n. iszero n 0 (length (tail (n (\p. make_list junk p) empty))) in
- let leq = \m n. iszero(n pred m) in
- let eq = \m n. and (leq m n)(leq n m) in
-
- ; a fixed-point combinator for defining recursive functions
- let Y = \f. (\h. f (h h)) (\h. f (h h)) in
-
- let length = Y (\length l. isempty l 0 (succ (length (tail l)))) in
-
- ; synonyms
- let makePair = make_pair in
- let nil = empty in
- let isNil = isempty in
- let makeList = make_list in
- let isZero = iszero in
- let mult = mul in
-
- ;
- length (tail mylist)
-</textarea>
-<input id="PARSE" value="Normalize" type="button">
-<input id="ETA" type="checkbox">do eta-reductions too
-<noscript><p>You may not see it because you have JavaScript turned off. Uffff!</p></noscript>
-<script src="/code/lambda.js"></script>
-<script src="/code/tokens.js"></script>
-<script src="/code/parse.js"></script>
-<script src="/code/json2.js"></script>
-<pre id="OUTPUT">
-</pre>
-<script>
-/*jslint evil: true */
-
-/*members create, error, message, name, prototype, stringify, toSource,
- toString, write
-*/
-
-/*global JSON, make_parse, parse, source, tree */
-
-// Make a new object that inherits members from an existing object.
-
-if (typeof Object.create !== 'function') {
- Object.create = function (o) {
- function F() {}
- F.prototype = o;
- return new F();
- };
-}
-
-// Transform a token object into an exception object and throw it.
-
-Object.prototype.error = function (message, t) {
- t = t || this;
- t.name = "SyntaxError";
- t.message = message;
- throw t;
-};
-
-
-(function () {
- var parse = make_parse();
-
- function go(source) {
- var string, tree, expr, eta;
- try {
- tree = parse(source);
- // string = JSON.stringify(tree, ['key', 'name', 'message', 'value', 'arity', 'first', 'second', 'third', 'fourth'], 4);
- expr = tree.handler();
- // string = JSON.stringify(expr, ['key', 'name', 'message', 'value', 'arity', 'first', 'second', 'tag', 'variable', 'left', 'right', 'bound', 'body' ], 4);
-// string = expr.to_string() + "\n\n~~>\n\n";
- string = '';
- eta = document.getElementById('ETA').checked;
- string = string + reduce(expr, eta, false).to_string();
- } catch (e) {
- string = JSON.stringify(e, ['name', 'message', 'from', 'to', 'key',
- 'value', 'arity', 'first', 'second', 'third', 'fourth'], 4);
- }
- document.getElementById('OUTPUT').innerHTML = string
- .replace(/&/g, '&')
- .replace(/[<]/g, '<');
- }
-
- document.getElementById('PARSE').onclick = function (e) {
- go(document.getElementById('INPUT').value);
- };
-}());
-
-</script>