Add :doc interpreter directive

schala-repl/src/language.rs

@@ -156,6 +156,9 @@ pub trait ProgrammingLanguageInterface {
   fn custom_interpreter_directives_help(&self) -> String {
     format!(">> No custom interpreter directives specified <<")
   }
+  fn get_doc(&mut self, _commands: &Vec<&str>) -> Option<String> {
+    None
+  }
 }
 
 /* a pass_chain function signature looks like: 

schala-repl/src/lib.rs

@@ -361,6 +361,7 @@ impl Repl {
         CommandTree::term("prev", None),
         CommandTree::NonTerminal(format!("go"), vec![], None)//TODO
       ], Some(format!("switch between languages, or go directly to a langauge by name"))),
+      CommandTree::term("doc", Some("Get language-specific help for an item")),
     ])
   }
 
@@ -437,6 +438,9 @@ impl Repl {
         Some(buf)
       },
       "debug" => self.handle_debug(commands),
+      "doc" => self.languages[self.current_language_index]
+        .get_doc(&commands)
+        .or(Some(format!("No docs implemented"))),
       e => self.languages[self.current_language_index]
         .handle_custom_interpreter_directives(&commands)
         .or(Some(format!("Unknown command: {}", e)))