finished inc and dec, and tests

src/stl.rs

@@ -349,6 +349,28 @@ pub fn static_stdlib(syms: &mut SymTable) -> Result<(), String> {
         },
     );
 
+    syms.insert(
+        "inc".to_string(),
+        Symbol {
+            name: String::from("inc"),
+            args: Args::Lazy(1),
+            conditional_branches: true,
+            docs: math::INC_DOCSTRING.to_string(),
+            value: ValueType::Internal(Rc::new(math::inc_callback)),
+        },
+    );
+
+    syms.insert(
+        "dec".to_string(),
+        Symbol {
+            name: String::from("dec"),
+            args: Args::Lazy(1),
+            conditional_branches: true,
+            docs: math::DEC_DOCSTRING.to_string(),
+            value: ValueType::Internal(Rc::new(math::dec_callback)),
+        },
+    );
+
     Ok(())
 }