Use throw() instead of returning errorObject() results directly

Add (type-of) for getting the string representation of an object's type.

src/env.c

@@ -242,6 +242,7 @@ struct Environment defaultEnv()
 #endif
 #ifdef STANDALONE
         pf(segfault),
+        pf(typeOf),
         pf(print),
         pf(numToChar),
         pf(printEnvO),

src/object.c

@@ -734,7 +734,7 @@ inline Object withLen(size_t len, enum Type type)
 inline Object constructLambda(const Object* params, const Object* body, struct Environment* env)
 {
     if (!params || !body) {
-        return errorObject(NULL_LAMBDA_LIST);
+        throw(NULL_LAMBDA_LIST, "fn params and body cannot be null");
     }
 
     if (params->type != TYPE_LIST) {

src/pebblemain.c

@@ -379,7 +379,7 @@ static Object run_script(Object* params, int length,
         free(code);
         return o;
     }
-    return errorObject(SCRIPT_NOT_FOUND);
+    throw(SCRIPT_NOT_FOUND, "");
 }
 
 static void code_window_unload(Window* window)

src/plfunc/general.c

@@ -277,7 +277,7 @@ int areEqual(const Object* obj1, const Object* obj2)
 Object equ(Object* params, int length, unused struct Environment* env)
 {
     if (length < 2) {
-        return errorObject(NOT_ENOUGH_ARGUMENTS);
+        throw(NOT_ENOUGH_ARGUMENTS, "expected at least 2");
     }
 
     for (int i = 0; i < length - 1; i++) {

src/plfunc/pc.c

@@ -12,6 +12,12 @@ Object print(Object* params, int length, unused struct Environment* env)
     return numberObject(0);
 }
 
+Object typeOf(Object* params, unused int length, unused struct Environment* env)
+{
+    const char* typeString = getTypeName(&(params[0]));
+    return nullTerminated(typeString);
+}
+
 Object numToChar(Object* params, unused int length, unused struct Environment* env)
 {
     checkTypes(numToChar);

src/plfunc/pc.h

@@ -7,6 +7,14 @@
 
 fn(print, "prn", "Prints the string representation of the given object to stdout.");
 
+tfn(typeOf, "type-of",
+    ({ anyType, returns(isStringy) }),
+    "Gets a string indicating the type of the given object",
+    "(type-of 10)", "TYPE_NUMBER",
+    "(type-of \"string\")", "TYPE_STRING",
+    "(type-of (fn () ()))", "TYPE_LAMBDA",
+);
+
 tfn(numToChar, "ch",
     ({ expect(isNumber), returns(isStringy) }),
     "Gets a string containing the ascii character for the given number value.",

src/plfunc/pebbleobject.c

@@ -94,7 +94,7 @@ Object addTextLayer(Object* params, int length, struct Environment* env)
     Object window = params[0];
     Object text = params[1];
     if (getPebbleType(window) != WINDOW) {
-        return errorObject(0);
+        throw(BAD_TYPE, "Expected a pebble window, but received %s", getTypeName(&window));
     }
     Layer* window_layer =
         window_get_root_layer(accessPebbleObject(window)->window);
@@ -179,6 +179,6 @@ Object doVibe(Object* params, int length, struct Environment* env)
             (VibePattern) {.durations = pattern, .num_segments = l});
         return trueObject();
     } else {
-        return errorObject(NOT_A_LIST);
+        throw(NOT_A_LIST, "(vibe) requires a non-empty list!");
     }
 }