Changes in api and upwards

- Removed out-of-stack error reporting
- Revised module system to match previous Orchid system
- Errors are now in a Vec everywhere
- Implemented atoms and lexer
- Started implementation of line parser
- Tree is now ephemeral to avoid copying Atoms held inside
- Moved numbers into std and the shared parser into base
- Started implementation of Commands

orchid-host/src/parse.rs

@@ -0,0 +1,33 @@
+use orchid_base::interner::Tok;
+
+use crate::tree::{OwnedItem, OwnedModule, OwnedTok, OwnedTokTree};
+
+pub struct ParseCtx<'a> {
+  tokens: &'a [OwnedTokTree]
+}
+
+pub fn split_br(ctx: ParseCtx) -> impl Iterator<Item = ParseCtx> {
+  ctx.tokens.split(|t| matches!(t.tok, OwnedTok::BR)).map(|tokens| ParseCtx { tokens })
+}
+
+pub fn strip_br(tt: &OwnedTokTree) -> Option<OwnedTokTree> {
+  let tok = match &tt.tok {
+    OwnedTok::BR => return None,
+    OwnedTok::Lambda(arg) => OwnedTok::Lambda(arg.iter().filter_map(strip_br).collect()),
+    OwnedTok::S(p, b) => OwnedTok::S(p.clone(), b.iter().filter_map(strip_br).collect()),
+    t => t.clone(),
+  };
+  Some(OwnedTokTree { tok, range: tt.range.clone() })
+}
+
+pub fn parse_items(ctx: ParseCtx) -> Vec<OwnedItem> {
+  todo!()
+}
+
+pub fn parse_item(ctx: ParseCtx) -> OwnedItem {
+  todo!()
+}
+
+pub fn parse_module(ctx: ParseCtx) -> (Tok<String>, OwnedModule) {
+  todo!()
+}