Working example

src/external/conv/parse_float.rs

@@ -0,0 +1,46 @@
+
+use chumsky::Parser;
+
+use std::fmt::Debug;
+use std::hash::Hash;
+
+use super::super::assertion_error::AssertionError;
+use crate::parse::float_parser;
+use crate::{atomic_impl, atomic_redirect, externfn_impl};
+use crate::foreign::ExternError;
+use crate::representations::{Primitive, Literal};
+use crate::representations::interpreted::Clause;
+
+/// ParseFloat a number
+/// 
+/// Next state: [ParseFloat0]
+
+#[derive(Clone)]
+pub struct ParseFloat1;
+externfn_impl!(ParseFloat1, |_: &Self, c: Clause| {Ok(ParseFloat0{c})});
+
+/// Applied to_string function
+/// 
+/// Prev state: [ParseFloat1]
+
+#[derive(Debug, Clone, PartialEq, Hash)]
+pub struct ParseFloat0{ c: Clause }
+atomic_redirect!(ParseFloat0, c);
+atomic_impl!(ParseFloat0, |Self{ c }: &Self| {
+  let literal: &Literal = c.try_into()
+    .map_err(|_| AssertionError::ext(c.clone(), "a literal value"))?;
+  let number = match literal {
+    Literal::Str(s) => {
+      let parser = float_parser();
+      parser.parse(s.as_str()).map_err(|_| AssertionError{
+        value: c.clone(), assertion: "cannot be parsed into a float"
+      }.into_extern())?
+    }
+    Literal::Num(n) => *n,
+    Literal::Uint(i) => (*i as u32).into(),
+    Literal::Char(char) => char.to_digit(10).ok_or(AssertionError{
+      value: c.clone(), assertion: "is not a decimal digit"
+    }.into_extern())?.into()
+  };
+  Ok(Clause::P(Primitive::Literal(Literal::Num(number))))
+});