diff --git a/src/builtins.c b/src/builtins.c
index c2384ef..4c32a1e 100644
--- a/src/builtins.c
+++ b/src/builtins.c
@@ -21,14 +21,14 @@ static struct Object *func_cdr(size_t args_count, struct Object **args_array);
 static struct Object *func_cons(size_t args_count, struct Object **args_array);
 static struct Object *func_list(size_t args_count, struct Object **args_array);
 // Type predicates
-static struct Object *func_booleanQN(size_t args_count, struct Object **args_array);
-static struct Object *func_charQN(size_t args_count, struct Object **args_array);
-static struct Object *func_nullQN(size_t args_count, struct Object **args_array);
-static struct Object *func_numberQN(size_t args_count, struct Object **args_array);
-static struct Object *func_pairQN(size_t args_count, struct Object **args_array);
-static struct Object *func_procedureQN(size_t args_count, struct Object **args_array);
-static struct Object *func_stringQN(size_t args_count, struct Object **args_array);
-static struct Object *func_symbolQN(size_t args_count, struct Object **args_array);
+static struct Object *func_boolean_QN(size_t args_count, struct Object **args_array);
+static struct Object *func_char_QN(size_t args_count, struct Object **args_array);
+static struct Object *func_null_QN(size_t args_count, struct Object **args_array);
+static struct Object *func_number_QN(size_t args_count, struct Object **args_array);
+static struct Object *func_pair_QN(size_t args_count, struct Object **args_array);
+static struct Object *func_procedure_QN(size_t args_count, struct Object **args_array);
+static struct Object *func_string_QN(size_t args_count, struct Object **args_array);
+static struct Object *func_symbol_QN(size_t args_count, struct Object **args_array);
 // Equivalence predicates
 static struct Object *func_equal_QN(size_t args_count, struct Object **args_array);
 // Type conversion
@@ -57,14 +57,14 @@ static struct Object builtins[] = {
     { .type = TYPE_PROCEDURE, .procedure = { "cons",            func_cons                  } },
     { .type = TYPE_PROCEDURE, .procedure = { "list",            func_list                  } },
     // Type predicates
-    { .type = TYPE_PROCEDURE, .procedure = { "boolean?",        func_booleanQN             } },
-    { .type = TYPE_PROCEDURE, .procedure = { "char?",           func_charQN                } },
-    { .type = TYPE_PROCEDURE, .procedure = { "null?",           func_nullQN                } },
-    { .type = TYPE_PROCEDURE, .procedure = { "number?",         func_numberQN              } },
-    { .type = TYPE_PROCEDURE, .procedure = { "pair?",           func_pairQN                } },
-    { .type = TYPE_PROCEDURE, .procedure = { "procedure?",      func_procedureQN           } },
-    { .type = TYPE_PROCEDURE, .procedure = { "string?",         func_stringQN              } },
-    { .type = TYPE_PROCEDURE, .procedure = { "symbol?",         func_symbolQN              } },
+    { .type = TYPE_PROCEDURE, .procedure = { "boolean?",        func_boolean_QN            } },
+    { .type = TYPE_PROCEDURE, .procedure = { "char?",           func_char_QN               } },
+    { .type = TYPE_PROCEDURE, .procedure = { "null?",           func_null_QN               } },
+    { .type = TYPE_PROCEDURE, .procedure = { "number?",         func_number_QN             } },
+    { .type = TYPE_PROCEDURE, .procedure = { "pair?",           func_pair_QN               } },
+    { .type = TYPE_PROCEDURE, .procedure = { "procedure?",      func_procedure_QN          } },
+    { .type = TYPE_PROCEDURE, .procedure = { "string?",         func_string_QN             } },
+    { .type = TYPE_PROCEDURE, .procedure = { "symbol?",         func_symbol_QN             } },
     // Equivalence predicates
     { .type = TYPE_PROCEDURE, .procedure = { "equal?",          func_equal_QN              } },
     // Type conversion
@@ -298,7 +298,7 @@ struct Object *func_list(
  * Type predicates *
  *******************/
 
-struct Object *func_booleanQN(
+struct Object *func_boolean_QN(
     const size_t args_count,
     struct Object **const args_array
 ) {
@@ -307,7 +307,7 @@ struct Object *func_booleanQN(
     return Object_new_boolean(object && object->type == TYPE_BOOLEAN);
 }
 
-struct Object *func_charQN(
+struct Object *func_char_QN(
     const size_t args_count,
     struct Object **const args_array
 ) {
@@ -316,7 +316,7 @@ struct Object *func_charQN(
     return Object_new_boolean(object && object->type == TYPE_CHAR);
 }
 
-struct Object *func_nullQN(
+struct Object *func_null_QN(
     const size_t args_count,
     struct Object **const args_array
 ) {
@@ -325,7 +325,7 @@ struct Object *func_nullQN(
     return Object_new_boolean(object == NULL);
 }
 
-struct Object *func_numberQN(
+struct Object *func_number_QN(
     const size_t args_count,
     struct Object **const args_array
 ) {
@@ -334,7 +334,7 @@ struct Object *func_numberQN(
     return Object_new_boolean(object && object->type == TYPE_NUMBER);
 }
 
-struct Object *func_pairQN(
+struct Object *func_pair_QN(
     const size_t args_count,
     struct Object **const args_array
 ) {
@@ -343,7 +343,7 @@ struct Object *func_pairQN(
     return Object_new_boolean(object && object->type == TYPE_PAIR);
 }
 
-struct Object *func_procedureQN(
+struct Object *func_procedure_QN(
     const size_t args_count,
     struct Object **const args_array
 ) {
@@ -352,7 +352,7 @@ struct Object *func_procedureQN(
     return Object_new_boolean(object && Object_is_procedure(object));
 }
 
-struct Object *func_stringQN(
+struct Object *func_string_QN(
     const size_t args_count,
     struct Object **const args_array
 ) {
@@ -361,7 +361,7 @@ struct Object *func_stringQN(
     return Object_new_boolean(object && object->type == TYPE_STRING);
 }
 
-struct Object *func_symbolQN(
+struct Object *func_symbol_QN(
     const size_t args_count,
     struct Object **const args_array
 ) {