implement process_release/1, process_wait/2, process_wait/3, and process_kill/1

src/machine/machine_errors.rs

@@ -405,6 +405,17 @@ impl MachineState {
                     [atom_as_cell((atom!("stream"))), cell(culprit)]
                 );
 
+                MachineError {
+                    stub,
+                    location: None,
+                }
+            }
+            ExistenceError::Process(culprit) => {
+                let stub = functor!(
+                    atom!("existence_error"),
+                    [atom_as_cell((atom!("process"))), cell(culprit)]
+                );
+
                 MachineError {
                     stub,
                     location: None,
@@ -1003,6 +1014,7 @@ pub enum ExistenceError {
     },
     SourceSink(HeapCellValue),
     Stream(HeapCellValue),
+    Process(HeapCellValue),
 }
 
 #[derive(Debug)]