[Rd] Feature Request: Allow Underscore Separated Numbers
Duncan Murdoch
murdoch@dunc@n @end|ng |rom gm@||@com
Sat Jul 16 17:17:17 CEST 2022
On 16/07/2022 5:24 a.m., Ivan Krylov wrote:
> On Fri, 15 Jul 2022 12:34:24 -0700
> Bill Dunlap <williamwdunlap using gmail.com> wrote:
>
>> The token '._1' (period underscore digit) is currently parsed as a
>> symbol (name). It would become a number if underscore were ignored
>> as in the first proposal. The just-between-digits alternative would
>> avoid this change.
>
> Thanks for spotting this! Here's a patch that allows underscores
> only between digits and only inside the significand of a number:
I think there's an issue with hex values. For example:
> 0xa_2
[1] 162
> 0x2_a
Error: unexpected input in "0x2_"
So "a" counts as a digit in 0xa_2, but not as a digit in 0x2_a.
Duncan Murdoch
>
> --- src/main/gram.y (revision 82598)
> +++ src/main/gram.y (working copy)
> @@ -2526,7 +2526,7 @@
> YYTEXT_PUSH(c, yyp);
> /* We don't care about other than ASCII digits */
> while (isdigit(c = xxgetc()) || c == '.' || c == 'e' || c == 'E'
> - || c == 'x' || c == 'X' || c == 'L')
> + || c == 'x' || c == 'X' || c == 'L' || c == '_')
> {
> count++;
> if (c == 'L') /* must be at the end. Won't allow 1Le3 (at present). */
> @@ -2538,11 +2538,16 @@
> if (count > 2 || last != '0') break; /* 0x must be first */
> YYTEXT_PUSH(c, yyp);
> while(isdigit(c = xxgetc()) || ('a' <= c && c <= 'f') ||
> - ('A' <= c && c <= 'F') || c == '.') {
> + ('A' <= c && c <= 'F') || c == '.' || c == '_') {
> if (c == '.') {
> if (seendot) return ERROR;
> seendot = 1;
> }
> + if (c == '_') {
> + /* disallow underscores following 0x or followed by non-digit */
> + if (nd == 0 || typeofnext() >= 2) break;
> + continue;
> + }
> YYTEXT_PUSH(c, yyp);
> nd++;
> }
> @@ -2588,6 +2593,11 @@
> break;
> seendot = 1;
> }
> + /* underscores in significand followed by a digit must be skipped */
> + if (c == '_') {
> + if (seenexp || typeofnext() >= 2) break;
> + continue;
> + }
> YYTEXT_PUSH(c, yyp);
> last = c;
> }
>
>
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