allow No to start identifier, but disallow all-No identifiers

Author: stevengj

src/flisp/julia_extensions.c

@@ -305,10 +305,11 @@ value_t fl_accum_julia_symbol(fl_context_t *fl_ctx, value_t *args, uint32_t narg
         type_error(fl_ctx, "accum-julia-symbol", "wchar", args[0]);
     uint32_t wc = *(uint32_t*)cp_data((cprim_t*)ptr(args[0]));
     ios_t str;
-    int allascii=1;
+    int allascii=1, allNo=1;
     ios_mem(&str, 0);
     do {
         allascii &= (wc <= 0x7f);
+        allNo = allNo && UTF8PROC_CATEGORY_NO == utf8proc_category((utf8proc_int32_t) wc);
         ios_getutf8(s, &wc);
         if (wc == '!') {
             uint32_t nwc;
@@ -324,6 +325,8 @@ value_t fl_accum_julia_symbol(fl_context_t *fl_ctx, value_t *args, uint32_t narg
             break;
     } while (jl_id_char(wc));
     ios_pututf8(&str, 0);
+    if (allNo) /* identifiers cannot consist only of category-No */
+        lerrorf(fl_ctx, symbol(fl_ctx, "error"), "invalid identifier %s", str.buf);
     return symbol(fl_ctx, allascii ? str.buf : normalize(fl_ctx, str.buf));
 }