diff --git a/implementations/C/KEYWORDS.txt b/implementations/C/KEYWORDS.txt
index fb222a6..08473de 100644
--- a/implementations/C/KEYWORDS.txt
+++ b/implementations/C/KEYWORDS.txt
@@ -172,6 +172,8 @@ _mape, def__mape
 _map0, def__map0
 _map1, def__map1
 _map2, def__map2
+_isnt_bool, def__isnt_bool
+_isnt_two_bools, def__isnt_two_bools
 _\/_, def___REVERSE_SOLIDUS_SOLIDUS__
 /\, def_SOLIDUS_REVERSE_SOLIDUS
 \/, def_REVERSE_SOLIDUS_SOLIDUS
diff --git a/implementations/C/definitions.c b/implementations/C/definitions.c
index 6df818a..e814bd3 100644
--- a/implementations/C/definitions.c
+++ b/implementations/C/definitions.c
@@ -135,6 +135,8 @@ JoyList def__mape_body;
 JoyList def__map0_body;
 JoyList def__map1_body;
 JoyList def__map2_body;
+JoyList def__isnt_bool_body;
+JoyList def__isnt_two_bools_body;
 JoyList def___REVERSE_SOLIDUS_SOLIDUS___body;
 JoyList def_SOLIDUS_REVERSE_SOLIDUS_body;
 JoyList def_REVERSE_SOLIDUS_SOLIDUS_body;
@@ -271,9 +273,11 @@ init_defs(void)
 	def__map0_body = text_to_expression("[_map1] dipd _map2");
 	def__map1_body = text_to_expression("stackd shift");
 	def__map2_body = text_to_expression("[infrst] cons dipd roll< swons");
-	def___REVERSE_SOLIDUS_SOLIDUS___body = text_to_expression("[not not] [not] branch");
-	def_SOLIDUS_REVERSE_SOLIDUS_body = text_to_expression("[not not] ii [pop false] [] branch");
-	def_REVERSE_SOLIDUS_SOLIDUS_body = text_to_expression("[not not] ii [] [pop true] branch");
+	def__isnt_bool_body = text_to_expression("not not");
+	def__isnt_two_bools_body = text_to_expression("[_isnt_bool] ii");
+	def___REVERSE_SOLIDUS_SOLIDUS___body = text_to_expression("[_isnt_bool] [not] branch");
+	def_SOLIDUS_REVERSE_SOLIDUS_body = text_to_expression("_isnt_two_bools [pop false] [] branch");
+	def_REVERSE_SOLIDUS_SOLIDUS_body = text_to_expression("_isnt_two_bools [] [pop true] branch");
 }
 
 
@@ -404,6 +408,8 @@ void def__mape(__attribute__((unused)) JoyListPtr stack, JoyListPtr expression)
 void def__map0(__attribute__((unused)) JoyListPtr stack, JoyListPtr expression) { push_quote_onto_expression(def__map0_body, expression); }
 void def__map1(__attribute__((unused)) JoyListPtr stack, JoyListPtr expression) { push_quote_onto_expression(def__map1_body, expression); }
 void def__map2(__attribute__((unused)) JoyListPtr stack, JoyListPtr expression) { push_quote_onto_expression(def__map2_body, expression); }
+void def__isnt_bool(__attribute__((unused)) JoyListPtr stack, JoyListPtr expression) { push_quote_onto_expression(def__isnt_bool_body, expression); }
+void def__isnt_two_bools(__attribute__((unused)) JoyListPtr stack, JoyListPtr expression) { push_quote_onto_expression(def__isnt_two_bools_body, expression); }
 void def___REVERSE_SOLIDUS_SOLIDUS__(__attribute__((unused)) JoyListPtr stack, JoyListPtr expression) { push_quote_onto_expression(def___REVERSE_SOLIDUS_SOLIDUS___body, expression); }
 void def_SOLIDUS_REVERSE_SOLIDUS(__attribute__((unused)) JoyListPtr stack, JoyListPtr expression) { push_quote_onto_expression(def_SOLIDUS_REVERSE_SOLIDUS_body, expression); }
 void def_REVERSE_SOLIDUS_SOLIDUS(__attribute__((unused)) JoyListPtr stack, JoyListPtr expression) { push_quote_onto_expression(def_REVERSE_SOLIDUS_SOLIDUS_body, expression); }
diff --git a/implementations/C/definitions.h b/implementations/C/definitions.h
index 012e2f7..5581a4d 100644
--- a/implementations/C/definitions.h
+++ b/implementations/C/definitions.h
@@ -126,6 +126,8 @@ void def__mape(JoyListPtr stack, JoyListPtr expression);
 void def__map0(JoyListPtr stack, JoyListPtr expression);
 void def__map1(JoyListPtr stack, JoyListPtr expression);
 void def__map2(JoyListPtr stack, JoyListPtr expression);
+void def__isnt_bool(JoyListPtr stack, JoyListPtr expression);
+void def__isnt_two_bools(JoyListPtr stack, JoyListPtr expression);
 void def___REVERSE_SOLIDUS_SOLIDUS__(JoyListPtr stack, JoyListPtr expression);
 void def_SOLIDUS_REVERSE_SOLIDUS(JoyListPtr stack, JoyListPtr expression);
 void def_REVERSE_SOLIDUS_SOLIDUS(JoyListPtr stack, JoyListPtr expression);
diff --git a/implementations/C/defs.txt b/implementations/C/defs.txt
index c211788..f4682da 100644
--- a/implementations/C/defs.txt
+++ b/implementations/C/defs.txt
@@ -126,6 +126,8 @@ _mape popd reverse
 _map0 [_map1] dipd _map2
 _map1 stackd shift
 _map2 [infrst] cons dipd roll< swons
-_\/_ [not not] [not] branch
-/\ [not not] ii [pop false] [] branch
-\/ [not not] ii [] [pop true] branch
\ No newline at end of file
+_isnt_bool not not
+_isnt_two_bools [_isnt_bool] ii
+_\/_ [_isnt_bool] [not] branch
+/\ _isnt_two_bools [pop false] [] branch
+\/ _isnt_two_bools [] [pop true] branch
diff --git a/implementations/C/keywords.c b/implementations/C/keywords.c
index d4625e5..eded4c8 100644
--- a/implementations/C/keywords.c
+++ b/implementations/C/keywords.c
@@ -99,9 +99,9 @@ in_word_set (register const char *str, register size_t len)
 {
   enum
     {
-      TOTAL_KEYWORDS = 163,
+      TOTAL_KEYWORDS = 165,
       MIN_WORD_LENGTH = 1,
-      MAX_WORD_LENGTH = 14,
+      MAX_WORD_LENGTH = 15,
       MIN_HASH_VALUE = 1,
       MAX_HASH_VALUE = 359
     };
@@ -216,7 +216,7 @@ in_word_set (register const char *str, register size_t len)
       {""},
 #line 132 "KEYWORDS.txt"
       {"second", def_second},
-#line 177 "KEYWORDS.txt"
+#line 179 "KEYWORDS.txt"
       {"\\/", def_REVERSE_SOLIDUS_SOLIDUS},
 #line 131 "KEYWORDS.txt"
       {"run", def_run},
@@ -234,7 +234,7 @@ in_word_set (register const char *str, register size_t len)
       {""},
 #line 137 "KEYWORDS.txt"
       {"spiral_next", def_spiral_next},
-#line 176 "KEYWORDS.txt"
+#line 178 "KEYWORDS.txt"
       {"/\\", def_SOLIDUS_REVERSE_SOLIDUS},
 #line 44 "KEYWORDS.txt"
       {"inscribe", inscribe},
@@ -402,12 +402,15 @@ in_word_set (register const char *str, register size_t len)
       {""},
 #line 94 "KEYWORDS.txt"
       {"fork", def_fork},
-      {""},
+#line 176 "KEYWORDS.txt"
+      {"_isnt_two_bools", def__isnt_two_bools},
 #line 15 "KEYWORDS.txt"
       {"=", def_eq},
 #line 21 "KEYWORDS.txt"
       {">=", def_ge},
-      {""}, {""}, {""},
+      {""}, {""},
+#line 175 "KEYWORDS.txt"
+      {"_isnt_bool", def__isnt_bool},
 #line 163 "KEYWORDS.txt"
       {"_step1", def__step1},
 #line 93 "KEYWORDS.txt"
@@ -454,7 +457,7 @@ in_word_set (register const char *str, register size_t len)
       {"reverse", def_reverse},
 #line 66 "KEYWORDS.txt"
       {"abs", def_abs},
-#line 175 "KEYWORDS.txt"
+#line 177 "KEYWORDS.txt"
       {"_\\/_", def___REVERSE_SOLIDUS_SOLIDUS__},
 #line 136 "KEYWORDS.txt"
       {"small", def_small},