Add a Boolean "not" operator.

Not wholly convinced this is a good idea, maybe "not" should be a
builtin function instead? 'not (.a == .b)' vs. '.a == .b | not'

c/compile.c

@@ -383,7 +383,11 @@ block gen_or(block a, block b) {
   block_append(&code, gen_condbranch(block_join(gen_op_simple(POP), gen_op_const(LOADK, jv_true())),
                                      if_a_false));
   return code;
-  
+}
+
+block gen_not(block a) {
+  return block_join(a, gen_condbranch(gen_op_const(LOADK, jv_false()),
+                                      gen_op_const(LOADK, jv_true())));
 }
 
 block gen_cond(block cond, block iftrue, block iffalse) {

c/compile.h

@@ -29,6 +29,7 @@ block gen_assign(block expr);
 block gen_definedor(block a, block b);
 block gen_and(block a, block b);
 block gen_or(block a, block b);
+block gen_not(block a);
 
 block gen_cond(block cond, block iftrue, block iffalse);
 

c/lexer.l

@@ -19,6 +19,7 @@
 "elif" { return ELSE_IF; }
 "and" { return AND; }
 "or" { return OR; }
+"not" { return NOT; }
 "end" { return END; }
 "//" { return DEFINEDOR; }
 "."|"="|";"|"["|"]"|","|":"|"("|")"|"{"|"}"|"|"|"+"|"\$" { return yytext[0];}

c/parser.y

@@ -36,6 +36,7 @@
 %token END "end"
 %token AND "and"
 %token OR "or"
+%token NOT "not"
 %right "//"
 %nonassoc '=' SETPIPE
 %nonassoc EQ
@@ -111,6 +112,10 @@ Exp "and" Exp {
   $$ = gen_and($1, $3);
 } |
 
+"not" Exp {
+  $$ = gen_not($2);
+} |
+
 Exp "//" Exp {
   $$ = gen_definedor($1, $3);
 } |

c/testdata

@@ -260,3 +260,7 @@ def inc(x): x |= .+1; inc(.[].a)
 [false,true]
 [false,true]
 [false,false]
+
+[.[] | not .]
+[1,0,false,null,true,"hello"]
+[false,false,true,true,false,false]