More examples, better defaults

grammar_separated is grammar but with all functions exposed

grammar_separated/src/custom_error.rs

@@ -0,0 +1,30 @@
+use std::fmt::Display;
+
+pub enum UserErrorTypes {
+    NumberTooBigUsize,
+    NumberTooBigi64,
+}
+
+impl Display for UserErrorTypes {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            | Self::NumberTooBigUsize => write!(
+                f,
+                "Specified number is too big (greater than {})",
+                usize::MAX
+            ),
+            | Self::NumberTooBigi64 => write!(
+                f,
+                "Specified number is too big (lesser than {} or \
+                           greater than {})",
+                i64::MIN,
+                i64::MAX
+            ),
+        }
+    }
+}
+
+pub struct UserError {
+    pub token: (usize, String, usize),
+    pub error: UserErrorTypes,
+}