Several changes, see commit msg

* clean up all tests
* bugfix for zero value functions, and test
* removed expand function, put in snippets
* added doc strings to Symbol type
* added doc strings to symbol declarations
* implemented display for Args type
* wrote a help function
* wrote docstrings for all builtins and config vars

tests/test_vars.rs

@@ -4,7 +4,7 @@ mod var_lib_tests {
 
     #[test]
     fn test_variable_def_and_lookup() {
-        let doc1 = "(def test 1)";
+        let doc1 = "(def test 'my test var' 1)";
         let doc2 = "(test)";
         let result = "(1)";
 
@@ -42,7 +42,7 @@ mod var_lib_tests {
 
     #[test]
     fn test_func_def_and_lookup() {
-        let doc1 = "(def test (hello) hello)";
+        let doc1 = "(def test 'my test func' (hello) hello)";
         let doc2 = "(test '1')";
         let result = "1";
 
@@ -79,8 +79,8 @@ mod var_lib_tests {
 
     #[test]
     fn test_variable_def_redef_and_lookup() {
-        let doc1 = "(def test 1)";
-        let doc2 = "(def test '2')";
+        let doc1 = "(def test 'my test var' 1)";
+        let doc2 = "(def test 'my test var' '2')";
         let doc3 = "(test)";
         let result = "('2')";
 
@@ -132,7 +132,7 @@ mod var_lib_tests {
 
     #[test]
     fn test_variable_def_undef_and_lookup_fail() {
-        let doc1 = "(def test 1)";
+        let doc1 = "(def test 'my test var' 1)";
         let doc2 = "(def test)";
         let doc3 = "(test)";
 
@@ -185,4 +185,41 @@ mod var_lib_tests {
             assert!(false);
         }
     }
+
+    #[test]
+    fn test_func_def_no_args() {
+        let doc1 = "(def test 'my test func' () '1')";
+        let doc2 = "(test)";
+        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);
+        }
+    }
 }