switched to lrpar parser generator

src/errors.rs

@@ -0,0 +1,19 @@
+use std::error::Error;
+use std::fmt::{Debug, Display, Formatter, Pointer};
+
+pub struct CLIArgumentError(pub &'static str);
+
+
+impl Display for CLIArgumentError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        f.write_str(self.0)
+    }
+}
+
+impl Debug for CLIArgumentError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
+impl Error for CLIArgumentError {}