X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=lambda_evaluator.mdwn;h=ffe1c9d589bcf8f0ea53b86cb5692ab4ba86622e;hp=4cf073616c23eca99b37672019949d79b5b93dfc;hb=f5940a5f1336b330235676932fcb70e038e75c8d;hpb=08e5cbb580b637a3e4c92fbb4fbb9f7891b81103

diff --git a/lambda_evaluator.mdwn b/lambda_evaluator.mdwn
index 4cf07361..ffe1c9d5 100644
--- a/lambda_evaluator.mdwn
+++ b/lambda_evaluator.mdwn
@@ -6,14 +6,32 @@ It will allow you to write lambda terms and evaluate them, with full ability to
 (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.)  
 
 *Lambda terms*: lambda terms are written with a backslash, thus: `((\x (\y x)) z)`.  
-If you click "Reduce", the system will produce a lambda term that is guaranteed to be reduction equivalent (`<~~>`) with the original term.  
+If you click "Reduce", the system will produce a lambda term that is guaranteed to be reduction equivalent (`<~~>`) with the original term.  So `((\x (\y x)) z)` reduces to (a lambda term equivalent to) `(\y z)`.
 
-*Let*: in order to make building a more elaborate system easier, it is possible to define values using `let`.
+*Let*: in order to make building a more elaborate set of terms easier, it is possible to define values using `let`.
 In this toy system, `let`s should only be used at the beginning of a file.  If we have, for intance,
 
     let true = (\x (\y x)) in
     let false = (\x (\y y)) in
+    ((true yes) no)
+
+the result is `yes`.  Things to watch out for: the expression after the equal sign must have balanced parentheses,
+and the "in" is obligatory.  If you violate these rules, the system will still produce a result, but it won't make much sense.
+
+*Abbreviations*: No abbreviations work.  So `\xy.yxx` must be written `(\x (\y ((y x) x)))`.  (As in Scheme or Racket.)
+
+*Comments*: anything following a semicolon to the end of the line is ignored.
+Blank lines are fine.
+
+Under the hood
+---------------
+
+The interpreter is written in JavaScript (which is not closely related to Java), and runs inside your browser.
+So if you decide to reduce a term that does not terminate (such as `((\x (x x)) (\x (x x)))`), it will be your 
+browser that stops responding, not the wiki server.
+
+You can inspect the code [here](http://lambda.jimpryor.net/code/lambda.js).  Suggestions for improvements welcome.
+
+Improvements we hope to add soon: the ability to reduce Combinatory Logic combinators; the ability to translate from CL to the lambda calculus; and more sensible variable names instead of `g354`.
 
-*Comments*:
 
-[more soon]