Merge pull request #14 from calcit-lang/dissoc-empty

fix dissoc of singleton to empty

Cargo.toml

@@ -1,7 +1,7 @@
 
 [package]
 name = "im_ternary_tree"
-version = "0.0.5"
+version = "0.0.6"
 edition = "2021"
 authors = ["jiyinyiyong <jiyinyiyong@gmail.com>"]
 license = "MIT"

examples/debug.rs

@@ -47,12 +47,16 @@ pub fn main() -> Result<(), String> {
   //   }
   // }
 
-  let mut data: Vec<usize> = vec![];
-  for idx in 0..110 {
-    data.push(idx);
-    let tree = TernaryTreeList::from(&data);
-    println!("{}", tree.format_inline());
-  }
+  // let mut data: Vec<usize> = vec![];
+  // for idx in 0..110 {
+  //   data.push(idx);
+  //   let tree = TernaryTreeList::from(&data);
+  //   println!("{}", tree.format_inline());
+  // }
+
+  let mut data: TernaryTreeList<usize> = TernaryTreeList::Empty;
+  data = data.push_right(0);
+  let _e = data.dissoc(0)?;
 
   Ok(())
 }

src/lib.rs

@@ -129,7 +129,13 @@ where
   pub fn dissoc(&self, idx: usize) -> Result<Self, String> {
     match self {
       Empty => Err(String::from("calling dissoc from empty")),
-      Tree(t) => Ok(TernaryTreeList::Tree(t.dissoc(idx)?)),
+      Tree(t) => {
+        if idx == 0 && t.len() == 1 {
+          Ok(TernaryTreeList::Empty)
+        } else {
+          Ok(TernaryTreeList::Tree(t.dissoc(idx)?))
+        }
+      }
     }
   }
   pub fn rest(&self) -> Result<Self, String> {

src/tree.rs

@@ -404,7 +404,7 @@ where
       return Err(format!("Index too large {} for {}", idx, self.len()));
     } else if self.len() == 1 {
       // idx already == 0
-      return Err(String::from("Cannot remove from singleton list"));
+      return Err(String::from("Cannot remove from singleton list to empty"));
     }
 
     match self {

tests/list_tests.rs

@@ -360,3 +360,12 @@ fn take_skip() -> Result<(), String> {
 
   Ok(())
 }
+
+#[test]
+fn dissoc_empty() -> Result<(), String> {
+  let data = TernaryTreeList::from(&[1]);
+
+  assert_eq!(data.dissoc(0).unwrap(), TernaryTreeList::Empty);
+
+  Ok(())
+}