From: Bart Schaefer <schaefer@brasslantern.com>
To: Stephane Chazelas <stephane.chazelas@gmail.com>,
"Zsh Hackers' List" <zsh-workers@zsh.org>
Subject: Re: [bug] $((0.5?1+1:3))
Date: Sun, 28 Apr 2013 21:15:42 -0700 [thread overview]
Message-ID: <130428211542.ZM14735@torch.brasslantern.com> (raw)
In-Reply-To: <20130429020002.GA7626@chaz.gmail.com>
On Apr 29, 3:00am, Stephane Chazelas wrote:
}
} That's quite an odd one. For any value of x between -1 and 1
} (-1, 1 and 0 excluded), $(( x ? <some-expression> : 42 )) where
} <some-expression> is anything but a numeric constant, expands to
} "0".
Hrm.
In math.c around line 1398 (varies a lot by version of zsh) we have
the "case QUEST:" that handles ternary expressions. There we find
this:
q = (stack[sp].val.type == MN_FLOAT) ? (zlong)stack[sp].val.u.d :
stack[sp].val.u.l;
Note this is rouding q down to an integer, so fractions less than one are
false. This is followed by:
if (!q)
noeval++;
mathparse(prec[COLON] - 1);
if (!q)
noeval--;
So the expression is consumed without parsing it. This "works" for
contatants by accident. Later when parsing is complete and the correct
non-zero-ness of the fraction is determined, the value of the unparsed
expression is substituted, which is almost always zero.
This should do it:
diff --git a/Src/math.c b/Src/math.c
index a2462a3..5bd4b90 100644
--- a/Src/math.c
+++ b/Src/math.c
@@ -1459,7 +1459,8 @@ mathparse(int pc)
case QUEST:
if (stack[sp].val.type == MN_UNSET)
stack[sp].val = getmathparam(stack + sp);
- q = (stack[sp].val.type == MN_FLOAT) ? (zlong)stack[sp].val.u.d :
+ q = (stack[sp].val.type == MN_FLOAT) ?
+ (stack[sp].val.u.d == 0 ? 0 : 1) :
stack[sp].val.u.l;
if (!q)
prev parent reply other threads:[~2013-04-29 4:15 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-29 2:00 Stephane Chazelas
2013-04-29 4:15 ` Bart Schaefer [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=130428211542.ZM14735@torch.brasslantern.com \
--to=schaefer@brasslantern.com \
--cc=stephane.chazelas@gmail.com \
--cc=zsh-workers@zsh.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/zsh/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).