diff --git a/Readme.org b/Readme.org
index d13758d..8d33218 100644
--- a/Readme.org
+++ b/Readme.org
@@ -160,7 +160,7 @@ Will need a concatenate function for tables
 **** TODO xor
 **** DONE no
 **** TODO eq?
-**** TODO toggle
+**** DONE toggle
 *** TODO string operations
 **** TODO typecast (string)
 **** TODO contains
diff --git a/src/stl.rs b/src/stl.rs
index ee9dba0..1f534dd 100644
--- a/src/stl.rs
+++ b/src/stl.rs
@@ -231,7 +231,7 @@ fn _store_callback(ast: &Seg, syms: &mut SymTable, env_cfg: bool) -> Result<Ctr,
                                     arg_syms: arg_list.clone(),
                                 }),
                                 name: identifier.clone(),
-                                args: Args::Strict(arg_list.into_iter().map(Type::from).collect()),
+                                args: Args::Lazy(arg_list.len() as u128),
                                 conditional_branches: false,
                             },
                         );
diff --git a/src/stl/boolean.rs b/src/stl/boolean.rs
index 675bc45..f0f39da 100644
--- a/src/stl/boolean.rs
+++ b/src/stl/boolean.rs
@@ -15,7 +15,7 @@
  */
 
 use crate::segment::{Ctr, Seg};
-use crate::sym::SymTable;
+use crate::sym::{SymTable, ValueType};
 
 pub fn bool_and_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
     let mut type_error = false;
@@ -71,6 +71,27 @@ pub fn bool_iseq_callback(_ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Strin
     todo!()
 }
 
-pub fn bool_toggle_callback(_ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
-    todo!()
+pub fn bool_toggle_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, String> {
+    let var_name: String;
+    if let Ctr::Symbol(ref s) = *ast.car  {
+         var_name = s.clone();
+    } else {
+        return Err("argument to toggle should be a symbol".to_string())
+    }
+
+    let mut sym = syms.remove(&var_name).expect(&format!("symbol {var_name} is not defined"));
+    if let ValueType::VarForm(ref var) = sym.value {
+        if let Ctr::Bool(ref b) = **var {
+            sym.value = ValueType::VarForm(Box::new(Ctr::Bool(!b)));
+        } else {
+            syms.insert(var_name, sym);
+            return Err("can only toggle a boolean".to_string())
+        }
+    } else {
+        syms.insert(var_name, sym);
+        return Err("cannot toggle a function".to_string())
+    }
+
+    syms.insert(var_name, sym);
+    Ok(Ctr::None)
 }
diff --git a/src/stl/control.rs b/src/stl/control.rs
index f6bb064..23d841e 100644
--- a/src/stl/control.rs
+++ b/src/stl/control.rs
@@ -116,9 +116,6 @@ pub fn let_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, String> {
                         return false
                     }
 
-                    let temp = var_val_res.clone().unwrap();
-                    println!("dbg: {}", temp);
-
                     localsyms.insert(name.clone(), Symbol {
                         name: name.clone(),
                         args: Args::None,
diff --git a/tests/test_lib_bools.rs b/tests/test_lib_bools.rs
index 0bc9af0..ce64efd 100644
--- a/tests/test_lib_bools.rs
+++ b/tests/test_lib_bools.rs
@@ -141,4 +141,101 @@ mod bool_lib_tests {
             assert!(false);
         }
     }
+
+    #[test]
+    fn test_toggle_a_bool() {
+        let document = "(def tester true)";
+        let change = "(toggle tester)";
+        let check = "(tester)";
+
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms).unwrap();
+        dynamic_stdlib(&mut syms).unwrap();
+
+        let doc_tree = lex(&document.to_string()).unwrap();
+        let change_tree = lex(&change.to_string()).unwrap();
+        let check_tree = lex(&check.to_string()).unwrap();
+
+        eval(&doc_tree, &mut syms).unwrap();
+        eval(&change_tree, &mut syms).unwrap();
+
+        if let Ctr::Seg(ref s) = *eval(&check_tree, &mut syms).unwrap() {
+            if let Ctr::Bool(ref b) = *s.car{
+                assert_eq!(false, *b)
+            } else {
+                panic!()
+            }
+        } else {
+            panic!()
+        }
+
+        eval(&change_tree, &mut syms).unwrap();
+        if let Ctr::Seg(ref s) = *eval(&check_tree, &mut syms).unwrap() {
+            if let Ctr::Bool(ref b) = *s.car{
+                assert_eq!(true, *b)
+            } else {
+                panic!()
+            }
+        } else {
+            panic!()
+        }
+    }
+
+    #[test]
+    fn test_toggle_errors_dont_lose_vars() {
+        let document = "(def tester 'oops')";
+        let change = "(toggle tester)";
+        let check = "(tester)";
+
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms).unwrap();
+        dynamic_stdlib(&mut syms).unwrap();
+
+        let doc_tree = lex(&document.to_string()).unwrap();
+        let change_tree = lex(&change.to_string()).unwrap();
+        let check_tree = lex(&check.to_string()).unwrap();
+
+        eval(&doc_tree, &mut syms).unwrap();
+        if let Err(s) = eval(&change_tree, &mut syms) {
+            assert_eq!(s, "error in call to toggle: can only toggle a boolean".to_string());
+            let intermediate = *eval(&check_tree, &mut syms).unwrap();
+            if let Ctr::Seg(ref s) = intermediate {
+                assert_eq!(s.to_string(), "('oops')".to_string());
+            } else {
+                eprintln!("did not expect: {}", intermediate);
+                panic!()
+            }
+        } else {
+            eprintln!("shouldn't have succeeded!");
+            panic!()
+        }
+    }
+
+    #[test]
+    fn test_toggle_errors_dont_lose_funcs() {
+        let document = "(def tester (oops) oops)";
+        let change = "(toggle tester)";
+        let check = "(tester '1')";
+
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms).unwrap();
+        dynamic_stdlib(&mut syms).unwrap();
+
+        let doc_tree = lex(&document.to_string()).unwrap();
+        let change_tree = lex(&change.to_string()).unwrap();
+        let check_tree = lex(&check.to_string()).unwrap();
+
+        eval(&doc_tree, &mut syms).unwrap();
+        if let Err(s) = eval(&change_tree, &mut syms) {
+            assert_eq!(s, "error in call to toggle: cannot toggle a function".to_string());
+            if let Ctr::String(ref s) = *eval(&check_tree, &mut syms).unwrap() {
+                assert_eq!(*s, "1".to_string());
+            } else {
+                panic!()
+            }
+        } else {
+            eprintln!("shouldn't have succeeded!");
+            panic!()
+        }
+    }
 }
diff --git a/tests/test_vars.rs b/tests/test_vars.rs
index 062ce35..eb5a800 100644
--- a/tests/test_vars.rs
+++ b/tests/test_vars.rs
@@ -40,6 +40,43 @@ mod var_lib_tests {
         }
     }
 
+    #[test]
+    fn test_func_def_and_lookup() {
+        let doc1 = "(def test (hello) hello)";
+        let doc2 = "(test '1')";
+        let result = "1";
+
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms).unwrap();
+        dynamic_stdlib(&mut syms).unwrap();
+
+        if let Ok(tree) = lex(&doc1.to_string()) {
+            let eval_result = *eval(&tree, &mut syms).unwrap();
+            if let Ctr::None = eval_result {
+                // pass
+            } else {
+                eprintln!("bad: {eval_result}");
+                assert!(false);
+            }
+        } else {
+            eprintln!("couldn't lex doc1");
+            assert!(false);
+        }
+
+        if let Ok(tree) = lex(&doc2.to_string()) {
+            let eval_result = *eval(&tree, &mut syms).unwrap();
+            if let Ctr::String(ref i) = eval_result {
+                assert_eq!(i.to_string(), result);
+            } else {
+                eprintln!("bad: {eval_result}");
+                assert!(false);
+            }
+        } else {
+            eprintln!("couldn't lex doc2");
+            assert!(false);
+        }
+    }
+
     #[test]
     fn test_variable_def_redef_and_lookup() {
         let doc1 = "(def test 1)";