Library support in interpreter (docs soon)

src/types.h

@@ -25,6 +25,7 @@ typedef enum ListAccessStatus {
 
 struct GroundValue;
 struct GroundFunction;
+struct GroundScope;
 
 struct List;
 
@@ -110,6 +111,11 @@ typedef struct GroundFunctionArgs {
     char* name;
 } GroundFunctionArgs;
 
+/*
+ * Native function pointer type.
+ */
+typedef GroundValue (*NativeGroundFunction)(struct GroundScope* scope, List args);
+
 /*
  * Represents a Ground function.
  */
@@ -119,6 +125,8 @@ typedef struct GroundFunction {
     GroundValueType returnType;
     GroundProgram program;
     size_t startLine;
+    bool isNative;
+    NativeGroundFunction nativeFn;
 } GroundFunction;