Add ns macro to change namespace from within clojurers

Author: Tko1

src/rust_core.rs

@@ -27,6 +27,10 @@ pub use self::_divide_::*;
 
 pub(crate) mod _multiply_;
 pub use self::_multiply_::*;
+
+pub(crate) mod ns;
+pub use self::ns::*;
+
 //
 // This module will hold core function and macro primitives that aren't special cases
 // (like the quote macro, or let), and can't be implemented in clojure itself
@@ -113,7 +117,7 @@ impl EvalFn {
         EvalFn {
             enclosing_environment,
         }
-    }
+    } 
 }
 impl ToValue for EvalFn {
     fn to_value(&self) -> Value {

src/rust_core/ns.rs

@@ -0,0 +1,41 @@
+use crate::ifn::IFn;
+use crate::value::{ToValue, Value};
+use crate::type_tag::TypeTag;
+use crate::environment::Environment;
+use std::rc::Rc;
+
+use crate::error_message;
+
+#[derive(Debug, Clone)]
+pub struct NsMacro {
+    enclosing_environment: Rc<Environment>
+}
+impl NsMacro {
+    pub fn new(enclosing_environment: Rc<Environment>) -> NsMacro {
+        NsMacro {
+            enclosing_environment,
+        }
+    } 
+}
+impl ToValue for NsMacro {
+    fn to_value(&self) -> Value {
+        Value::Macro(Rc::new(self.clone()))
+    }
+}
+impl IFn for NsMacro {
+    fn invoke(&self, args: Vec<Rc<Value>>) -> Value {
+	if args.len() != 1 {
+	    return error_message::wrong_arg_count(1,args.len());
+	}
+	
+	let namespace = args.get(0).unwrap();
+	match &**namespace {
+	    Value::Symbol(sym) => { 
+		self.enclosing_environment.change_namespace(sym.clone());
+		Value::Nil
+	    },
+	    _ => error_message::type_mismatch(TypeTag::Symbol,&**namespace)
+	}
+	    
+    }
+}