json: support forgotten null object.

The JSON null will map to the Lisp null symbol.  I thought
about using : but that could cause surprises; like when it's
passed to functions as an optional argument, it will trigger
the default value.

* parser.l (JSON): Add rules for producing null keyword.

* txr.1: Documented.

* lex.yy.c.shipped: Updated.

1 files changed, 10 insertions, 0 deletions

diff --git a/parser.l b/parser.l
index 86472c03..c0532dc6 100644
--- a/parser.l
+++ b/parser.l
@@ -1194,6 +1194,11 @@ NJPUNC  [^(){},:\[\]"~*^ \t\n]
   return JSKW;
 }
 
+<JSON>null/({JPUNC}|[ \t\n]) {
+  yylval->val = null_s;
+  return JSKW;
+}
+
 <JSON>{NJPUNC}+ {
   if (strcmp("true", yytext) == 0) {
     yylval->val = t;
@@ -1205,6 +1210,11 @@ NJPUNC  [^(){},:\[\]"~*^ \t\n]
     return JSKW;
   }
 
+  if (strcmp("null", yytext) == 0) {
+    yylval->val = null_s;
+    return JSKW;
+  }
+
   {
     val str = string_own(utf8_dup_from(yytext));
     yyerrorf(yyg, lit("unrecognized JSON syntax: ~a"), str, nao);