repline: Promote to its own crate!

cl-repl: Major refactor based on the design of typeck.rs

src/iter.rs

@@ -0,0 +1,68 @@
+//! Shmancy iterator adapters
+
+pub use chars::Chars;
+pub use flatten::Flatten;
+
+pub mod chars {
+    //! Converts an <code>[Iterator]<Item = [u8]></code> into an
+    //! <code>[Iterator]<Item = [Result]<[char], [BadUnicode]>></code>
+
+    /// Invalid unicode codepoint found when iterating over [Chars]
+    #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+    pub struct BadUnicode(pub u32);
+    impl std::error::Error for BadUnicode {}
+    impl std::fmt::Display for BadUnicode {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            let Self(code) = self;
+            write!(f, "Bad unicode: {code}")
+        }
+    }
+
+    /// Converts an <code>[Iterator]<Item = [u8]></code> into an
+    /// <code>[Iterator]<Item = [char]></code>
+    #[derive(Clone, Debug)]
+    pub struct Chars<I: Iterator<Item = u8>>(pub I);
+    impl<I: Iterator<Item = u8>> Iterator for Chars<I> {
+        type Item = Result<char, BadUnicode>;
+        fn next(&mut self) -> Option<Self::Item> {
+            let Self(bytes) = self;
+            let start = bytes.next()? as u32;
+            let (mut out, count) = match start {
+                start if start & 0x80 == 0x00 => (start, 0), // ASCII valid range
+                start if start & 0xe0 == 0xc0 => (start & 0x1f, 1), // 1 continuation byte
+                start if start & 0xf0 == 0xe0 => (start & 0x0f, 2), // 2 continuation bytes
+                start if start & 0xf8 == 0xf0 => (start & 0x07, 3), // 3 continuation bytes
+                _ => return None,
+            };
+            for _ in 0..count {
+                let cont = bytes.next()? as u32;
+                if cont & 0xc0 != 0x80 {
+                    return None;
+                }
+                out = out << 6 | (cont & 0x3f);
+            }
+            Some(char::from_u32(out).ok_or(BadUnicode(out)))
+        }
+    }
+}
+pub mod flatten {
+    //! Flattens an [Iterator] returning [`Result<T, E>`](Result) or [`Option<T>`](Option)
+    //! into a *non-[FusedIterator](std::iter::FusedIterator)* over `T`
+
+    /// Flattens an [Iterator] returning [`Result<T, E>`](Result) or [`Option<T>`](Option)
+    /// into a *non-[FusedIterator](std::iter::FusedIterator)* over `T`
+    #[derive(Clone, Debug)]
+    pub struct Flatten<T, I: Iterator<Item = T>>(pub I);
+    impl<T, E, I: Iterator<Item = Result<T, E>>> Iterator for Flatten<Result<T, E>, I> {
+        type Item = T;
+        fn next(&mut self) -> Option<Self::Item> {
+            self.0.next()?.ok()
+        }
+    }
+    impl<T, I: Iterator<Item = Option<T>>> Iterator for Flatten<Option<T>, I> {
+        type Item = T;
+        fn next(&mut self) -> Option<Self::Item> {
+            self.0.next()?
+        }
+    }
+}