Now `Closure`s are not a new kind of lambda _term_: the syntax for our language doesn't have any constituents that get parsed into `Closure`s. `Closure`s are only created _during the course of evaluating_ terms: specifically, when a variable gets bound to an abstract, which may itself contain variables that are locally free (not bound by the abstract itself). This is why we have separate datatypes for _terms_ and for the _results_ that terms can evaluate to. `Closure`s are results, but they aren't terms. `App`s are terms, but not results. Our boolean and number literals, as well as our primitive functions, constructors, and destructors, are both.
+In later weeks, we will see more examples of results that aren't terms, but can only be generated during the course of a computation. (I'm thinking of mutable reference cells. Arguably, partially applied constructors are yet another example, that we're already familiar with.)
+
Getting, reading, and compiling the source code
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-You can download the source code for the intepreter [[here|/code/untyped_full-1.3.tgz]]. That link will always give you the latest version. We will update it as we find any issues. Let us know about any difficulties you experience.
+You can download the source code for the intepreter [[here|/code/untyped_full-1.7.tgz]]. That link will always give you the latest version. We will update it as we find any issues. Let us know about any difficulties you experience.
When you unpack the downloaded source code, you will get a folder with the following contents, sorted here by logical order rather than alphabetically.
ocamlc -o interp.exe lolevel.cmo types.cmo hilevel.cmo primitives.cmo \
engine.cmo parser.cmo lexer.cmo main.cmo
-If your computer doesn't ... TODO
-
OK, I built the interpeter. How can I use it?
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/* note that it's not f x (g y) (h z) */
"strings" /* you can input these and pass them around, but can't perform any operations on them */
-Predefined combinators include: `S`, `K` (same as `const`), `I` (same as `id`), `B` (same as `(o)`, occurring in prefix not infix position), `C` (same as `flip`), `T`, `V` (the Church pairing combinator), `W`, `M` (better known as `ω`), and `L`.
+Predefined combinators include: `S`, `K` (same as `const`), `I` (same as `id`), `B` (same as `(o)`, occurring in prefix not infix position), `C` (same as `flip`), `T` (same as `flip ($)`), `V` (the Church pairing combinator), `W`, `M` (better known as `ω`), and `L`.
The parser also accepts `letrec ... in ...` terms, but currently there is no implementation for how to reduce/interpret these (that's for a later assignment), so you'll just get an error.