Add +zing jet

rust/ares/src/jets/text.rs

@@ -8,14 +8,24 @@ use crate::noun::{Noun, D};
 crate::gdb!();
 
 pub fn jet_lent(_context: &mut Context, subject: Noun) -> Result {
-    let tape = slot(subject, 6)?;
-    util::lent(tape).map(|x| D(x as u64))
+    let list = slot(subject, 6)?;
+    util::lent(list).map(|x| D(x as u64))
+}
+
+pub fn jet_zing(context: &mut Context, subject: Noun) -> Result {
+    let list = slot(subject, 6)?;
+    let stack = &mut context.stack;
+
+    util::zing(stack, list)
 }
 
 pub mod util {
     use crate::interpreter::Error;
+    use crate::jets;
     use crate::jets::JetErr;
-    use crate::noun::{Noun, D};
+    use crate::mem::NockStack;
+    use crate::noun::{Noun, Cell, D};
+    use std::result::Result;
 
     pub fn lent(tape: Noun) -> Result<usize, JetErr> {
         let mut len = 0usize;
@@ -35,6 +45,54 @@ pub mod util {
         }
         Ok(len)
     }
+
+    pub fn zing(stack: &mut NockStack, mut list: Noun) -> jets::Result {
+        unsafe {
+            let (mut new_cell, mut new_memory) = Cell::new_raw_mut(stack);
+            #[allow(unused_assignments)]
+            let (mut cell, mut memory) = (new_cell, new_memory);
+            let mut res: Noun = D(0);
+            let mut flag = false;
+    
+            loop {
+                if list.raw_equals(D(0)) {
+                    break;
+                }
+    
+                let pair = list.as_cell()?;
+                let mut sub_list = pair.head();
+    
+                loop {
+                    if sub_list.raw_equals(D(0)) {
+                        break;
+                    }
+    
+                    let elem = sub_list.as_cell()?;
+                    let head = elem.head();
+    
+                    if flag {
+                        (new_cell, new_memory) = Cell::new_raw_mut(stack);
+                        (*memory).tail = new_cell.as_noun();
+                        memory = new_memory;
+                    } else {
+                        (cell, memory) = Cell::new_raw_mut(stack);
+                        res = cell.as_noun();
+                        flag = true;
+                    }
+                    (*memory).head = head;
+    
+                    sub_list = elem.tail();
+                }
+    
+                list = pair.tail();
+            }
+            
+            if flag {
+                (*new_memory).tail = D(0);
+            }
+            Ok(res)
+        }
+    }
 }
 
 #[cfg(test)]
@@ -58,4 +116,21 @@ mod tests {
         let sam = T(&mut c.stack, &[D(3), D(2), D(1)]);
         assert_jet_err(c, jet_lent, sam, JetErr::Fail(Error::Deterministic(D(0))));
     }
+
+    #[test]
+    fn test_zing() {
+        let c = &mut init_context();
+
+        let list_0 = T(&mut c.stack, &[D(0), D(0), D(0), D(0)]);
+        let list_1 = T(&mut c.stack, &[D(1), D(2), D(3), D(0)]);
+        let list_2 = T(&mut c.stack, &[D(4), D(5), D(6), D(0)]);
+        let list_3 = T(&mut c.stack, &[D(1), D(2), D(3), D(4), D(5), D(6), D(0)]);
+
+        assert_jet(c, jet_zing, D(0), D(0));
+        assert_jet(c, jet_zing, list_0, D(0));
+        let sam = T(&mut c.stack, &[list_0, D(0)]);
+        assert_jet(c, jet_zing, sam, list_0);
+        let sam = T(&mut c.stack, &[list_1, list_2, D(0)]);
+        assert_jet(c, jet_zing, sam, list_3);
+    }
 }