From: Daniel Shahaf <d.s@daniel.shahaf.name>
To: zsh-workers@zsh.org
Subject: Re: inf and nan in arithmetic expansions
Date: Sat, 17 Feb 2018 00:38:52 +0000 [thread overview]
Message-ID: <1518827932.2163403.1273708688.6920FBA8@webmail.messagingengine.com> (raw)
In-Reply-To: <17756.1518799875@thecus.kiddle.eu>
Oliver Kiddle wrote on Fri, 16 Feb 2018 17:51 +0100:
> > And then we could add 'inf' and 'nan' as readonly variables initialised to
> > those respective values (as Oliver also suggests in the 19597 thread). There
> > are compatibility implications for scripts that use these variable names, but
> > there is no way around them if we want to allow explicitly doing (( x = inf ))
> > in user code...
>
> I'm not sure about making them readonly simply because not doing so is
> less likely to break an existing script.
After 42356 I am not sure whether I would prefer predefined variables
(readonly or not) or recognising 'inf' and 'nan' (putting aside the
question of case for a moment) as special constants in math contexts
as 42356 suggests.
> @@ -791,6 +822,21 @@ zzlex(void)
> break;
> /* Fall through! */
Unrelated to the patch: that comment is incorrect.
> default:
> + if (strcmp(ptr-1, "NaN") == 0) {
> + yyval.type = MN_FLOAT;
> + yyval.u.d = 0.0;
> + yyval.u.d /= yyval.u.d;
> + ptr += 2;
> + return NUM;
> + }
> + else if (strcmp(ptr-1, "Inf") == 0) {
> + yyval.type = MN_FLOAT;
> + yyval.u.d = 0.0;
> + yyval.u.d = 1.0 / yyval.u.d;
> + ptr += 2;
> + return NUM;
> + }
> +
> if (idigit(*--ptr) || *ptr == '.')
> return lexconstant();
> if (*ptr == '#') {
next prev parent reply other threads:[~2018-02-17 0:39 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-07 22:30 Stephane Chazelas
2018-02-07 23:25 ` Oliver Kiddle
2018-02-08 9:38 ` Peter Stephenson
2018-02-08 12:46 ` Daniel Shahaf
2018-02-08 14:22 ` Stephane Chazelas
2018-02-09 15:31 ` Daniel Shahaf
2018-02-09 21:09 ` Stephane Chazelas
2018-02-10 0:10 ` Bart Schaefer
2018-02-16 16:51 ` Oliver Kiddle
2018-02-17 0:38 ` Daniel Shahaf [this message]
2018-02-19 14:19 ` Stephane Chazelas
2018-02-27 13:02 ` Vincent Lefevre
2018-02-27 15:25 ` Oliver Kiddle
2018-02-27 16:56 ` Vincent Lefevre
2018-03-21 23:46 ` Oliver Kiddle
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