edits

[lambda.git] / lambda_evaluator.mdwn

diff --git a/lambda_evaluator.mdwn b/lambda_evaluator.mdwn
index 1ca957b..4a5b9dc 100644 (file)
--- a/lambda_evaluator.mdwn
+++ b/lambda_evaluator.mdwn
@@ -1,6 +1,3 @@
-Lambda Evaluator
-----------------
-
 This lambda evaluator will allow you to write lambda terms and evaluate (that is, normalize) them, and inspect the results.
 (This won't work in Racket, because Racket doesn't even try to represent the internal structure of a function in a human-readable way.)  
 
@@ -22,7 +19,7 @@ Blank lines are fine.
 
 *Abbreviations*: In an earlier version, you couldn't use abbreviations. `\x y. y x x` had to be written `(\x (\y ((y x) x)))`. We've upgraded the parser though, so now it should be able to understand any lambda term that you can.
 
-*Constants*:  (NOT YET IMPLEMENTED!) The combinators `S`, `K`, `I`, `C`, `B`, `W`, and `T` are pre-defined to their standard values. Also, integers will automatically be converted to Church numerals. (`0` is `\s z. z`, `1` is `\s z. s z`, and so on.)
+*Constants*: The combinators `S`, `K`, `I`, `C`, `B`, `W`, and `T` are pre-defined to their standard values. Also, integers will automatically be converted to Church numerals. (`0` is `\s z. z`, `1` is `\s z. s z`, and so on.)
 
 
 
@@ -38,11 +35,12 @@ let and = \l r. l r false in
 )
 </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 language=JavaScript src="code/tokens.js"></script>
-<script language=JavaScript src="code/parse.js"></script>
-<script language=JavaScript src="code/lambda.js"></script>
-<script language=JavaScript src="code/json2.js"></script>
+<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>
@@ -78,12 +76,16 @@ Object.prototype.error = function (message, t) {
     var parse = make_parse();
 
     function go(source) {
-        var string, tree;
+        var string, tree, expr, eta;
         try {
             tree = parse(source);
-//             string = JSON.stringify(tree, ['key', 'name', 'message', 'value', 'arity', 'first', 'second', 'third', 'fourth'], 4);
-//             string = JSON.stringify(tree.handler(), ['key', 'name', 'message', 'value', 'arity', 'first', 'second', 'tag', 'variable', 'left', 'right', 'bound', 'body' ], 4);
-                       string = tree.handler().to_string();
+ //           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);
@@ -119,5 +121,4 @@ The code is based on:
 
 Improvements we hope to add soon: the ability to reduce Combinatory Logic combinators and report the result as combinators, rather than in lambda forms.
 
-For these assignments, you'll probably want to use a "lambda calculator" to check your work. This accepts any grammatical lambda expression and reduces it to normal form, when possible. See our [lambda-let page](/lambda-let.html),