Initial commit

Basic GNU standard files are added, and we now stop worrying about
monadic anamorphisms.

The current focus is on testing the correctness of the algorithm, so I
need convenient support for manipulating, interpreting, examining, and
per chance animating nondeterministic automata.

1 files changed, 26 insertions, 0 deletions

diff --git a/graph/src/error.rs b/graph/src/error.rs
new file mode 100644
index 0000000..2162685
--- /dev/null
+++ b/graph/src/error.rs
@@ -0,0 +1,26 @@
+#![warn(missing_docs)]
+//! This file implements the error data type of the graph library.
+
+use std::fmt::{self, Display};
+
+/// The error type for methods of the trait [`Graph`][`super::Graph`].
+#[derive(Debug, Clone, PartialEq, Eq, Ord, PartialOrd)]
+pub enum Error {
+    /// The index is out of bounds.
+    ///
+    /// The first component is the index that is out of bounds, and
+    /// the second component is the current length of nodes.
+    IndexOutOfBounds(usize, usize),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Error::IndexOutOfBounds(index, len) => {
+                write!(f, "index {index} out of bounds {len} ")
+            }
+        }
+    }
+}
+
+impl std::error::Error for Error {}