Most files suffered major changes

- Less ambiguous syntax
- Better parser (Chumsky only does tokenization now)
- Tidy(|ier) error handling
- Facade for simplified embedding
- External code grouped in (fairly) self-contained Systems
- Dynamic action dispatch
- Many STL additions

src/systems/stl/conv.rs

@@ -0,0 +1,58 @@
+use chumsky::Parser;
+use ordered_float::NotNan;
+
+use super::ArithmeticError;
+use crate::foreign::ExternError;
+use crate::interner::Interner;
+use crate::parse::{float_parser, int_parser};
+use crate::systems::cast_exprinst::with_lit;
+use crate::systems::AssertionError;
+use crate::{define_fn, ConstTree, Literal};
+
+define_fn! {
+  /// parse a number. Accepts the same syntax Orchid does.
+  ToFloat = |x| with_lit(x, |l| match l {
+    Literal::Str(s) => float_parser()
+      .parse(s.as_str())
+      .map_err(|_| AssertionError::ext(
+        x.clone(),
+        "cannot be parsed into a float"
+      )),
+    Literal::Num(n) => Ok(*n),
+    Literal::Uint(i) => NotNan::new(*i as f64)
+      .map_err(|_| ArithmeticError::NaN.into_extern()),
+  }).map(|nn| Literal::Num(nn).into())
+}
+
+define_fn! {
+  /// Parse an unsigned integer. Accepts the same formats Orchid does. If the
+  /// input is a number, floors it.
+  ToUint = |x| with_lit(x, |l| match l {
+    Literal::Str(s) => int_parser()
+      .parse(s.as_str())
+      .map_err(|_| AssertionError::ext(
+        x.clone(),
+        "cannot be parsed into an unsigned int",
+      )),
+    Literal::Num(n) => Ok(n.floor() as u64),
+    Literal::Uint(i) => Ok(*i),
+  }).map(|u| Literal::Uint(u).into())
+}
+
+define_fn! {
+  /// Convert a literal to a string using Rust's conversions for floats, chars and
+  /// uints respectively
+  ToString = |x| with_lit(x, |l| Ok(match l {
+    Literal::Uint(i) => i.to_string(),
+    Literal::Num(n) => n.to_string(),
+    Literal::Str(s) => s.clone(),
+  })).map(|s| Literal::Str(s).into())
+}
+
+pub fn conv(i: &Interner) -> ConstTree {
+  ConstTree::tree([
+    (i.i("to_float"), ConstTree::xfn(ToFloat)),
+    (i.i("to_uint"), ConstTree::xfn(ToUint)),
+    (i.i("to_string"), ConstTree::xfn(ToString)),
+  ])
+}