revert spawn! as a special form

may_2025_thoughts.md

@@ -1208,3 +1208,34 @@ After that:
     - [x] read inputs?
     - [x] load url text?
 
+### Following links
+#### 2025-07-05
+Doing some last minute design work on linking processes.
+Here's the erlang way:
+* `link` is `link/1`: we always link _from a process_.
+* links are always bidirectional
+* [ ] update the link API to reflect this
+* There's the concept of an exit signal
+    - erlang has three ways of doing this (ish): `:normal` (returning), `:kill` (panic), or a reason (which is a value).
+    - you can "trap" an exit signal that's `:normal` or a reason, but not if it's `:kill`, which will bring down the monitoring process
+* I think in ludus we want...
+
+Well? What do we want?
+
+Erlang and Elixir have designs that are meant for massively concurrent processes.
+In addition, I've been thinking about how the willy-nilly, anything goes, messages getting passed around all kinds of places, actually cuts against the spirit of Ludus.
+What sort of process management, abstraction, modelling, and mental-modelling do we want in ludus?
+My sense is that, actually, I have to build the things we're going to build before I have a sense of what needs doing.
+`link` may not even be a thing we need?
+
+Anyway, here's the tl;dr for basic process linking:
+* `link/1` should establish a bidirectional link, bringing one process down if the other exits for any reason, causing a panic if the linked process exits unexpectedly, even on a normal return
+* `monitor/1` means we can monitor exit messages, these will be `(:exit, pid, (:ok, value))` in the case of successful return, or `(:exit, pid, (:err, msg))` in the case of a panic. These are sent as normal messages to the monitoring process.
+
+Erlang/Elixir has a lot more, but that's basically it for Ludus for now.
+`monitor/1` makes it easy to write an `await`.
+
+As I'm thinking about this, I actually want to roll back `spawn` as a special form.
+I think it's actually a good cognitive shift to understand that functions are reified, deferred computations.
+And that processes take this a long way.
+We can revisit the idea of a special spawn form later.

src/lexer.rs

@@ -76,7 +76,7 @@ pub fn lexer(
         "nil" => Token::Nil,
         // todo: hard code these as type constructors
         "as" | "box" | "do" | "else" | "fn" | "if" | "let" | "loop" | "match" | "panic!"
-        | "recur" | "repeat" | "then" | "when" | "with" | "or" | "and" | "receive" | "spawn!" => {
+        | "recur" | "repeat" | "then" | "when" | "with" | "or" | "and" | "receive" => {
             Token::Reserved(word)
         }
         _ => Token::Word(word),