comparing begin and end offsets for top-level sections and headlines.

src/compare/sexp.rs

@@ -1,3 +1,5 @@
+use std::collections::HashMap;
+
 use nom::branch::alt;
 use nom::bytes::complete::escaped;
 use nom::bytes::complete::tag;
@@ -44,6 +46,31 @@ impl<'s> Token<'s> {
             _ => Err("wrong token type"),
         }?)
     }
+
+    pub fn as_map<'p>(
+        &'p self,
+    ) -> Result<HashMap<&'s str, &'p Token<'s>>, Box<dyn std::error::Error>> {
+        let mut hashmap = HashMap::new();
+
+        let children = self.as_list()?;
+        if children.len() % 2 != 0 {
+            return Err("Expecting an even number of children".into());
+        }
+        let mut key: Option<&str> = None;
+        for child in children.iter() {
+            match key {
+                None => {
+                    key = Some(child.as_atom()?);
+                }
+                Some(key_val) => {
+                    key = None;
+                    hashmap.insert(key_val, child);
+                }
+            };
+        }
+
+        Ok(hashmap)
+    }
 }
 
 #[tracing::instrument(ret, level = "debug")]