From: Peter Stephenson <p.w.stephenson@ntlworld.com>
To: jdh <dhenman@gmail.com>, zsh-workers@zsh.org
Subject: Re: Math expression evaluation error?
Date: Fri, 9 Jan 2015 22:40:34 +0000 [thread overview]
Message-ID: <20150109224034.294d4fd6@ntlworld.com> (raw)
In-Reply-To: <54B04ADA.9050102@gmail.com>
On Fri, 09 Jan 2015 13:40:42 -0800
jdh <dhenman@gmail.com> wrote:
> Thanks for the detailed explanation. I suggest that the an additional
> line be added to the manual, which would say something like:
>
> " Caution: The evaluation of an expression is taken a term at a time
> and if there are mixed terms , say integer only and float terms , the
> integer only ones will not be promoted to real values and the result of
> the whole expression would be an error to common standards. One can use
> the -f option or the FORCE_FLOAT environment variable to change this
> behavior."
Thanks, that's just the sort of useful feedback on what people find
confusing that we need. I've adapted it into the appropriate section of
the manual with minor corrections.
diff --git a/Doc/Zsh/arith.yo b/Doc/Zsh/arith.yo
index a620b73..5c334ce 100644
--- a/Doc/Zsh/arith.yo
+++ b/Doc/Zsh/arith.yo
@@ -233,6 +233,15 @@ necessary. In addition, if any operator which requires an integer
equivalents with assignment) is given a floating point argument, it will be
silently rounded down to the next integer.
+Users should beware that, in common with many other programming
+languages but not software designed for calculation, the evaluation of
+an expression in zsh is taken a term at a time and promotion of integers
+to floating point does not occur in terms only containing integers. A
+typical result of this is that a division such as tt(6/8) is truncated,
+in this being rounded down to 0. The tt(FORCE_FLOAT) shell option can
+be used in scripts or functions where floating point evaluation is
+required throughout.
+
Scalar variables can hold integer or floating point values at different
times; there is no memory of the numeric type in this case.
pws
next prev parent reply other threads:[~2015-01-09 22:40 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-09 19:46 jdh
2015-01-09 20:15 ` Peter Stephenson
2015-01-09 21:40 ` jdh
2015-01-09 22:19 ` Ray Andrews
2015-01-09 23:06 ` Lawrence Velázquez
2015-01-09 23:52 ` Ray Andrews
2015-01-10 0:25 ` Bart Schaefer
2015-01-10 7:27 ` Ray Andrews
2015-01-10 16:53 ` Bart Schaefer
2015-01-10 18:48 ` Ray Andrews
2015-01-10 19:14 ` Bart Schaefer
2015-01-10 22:21 ` Ray Andrews
2015-01-11 1:51 ` Bart Schaefer
2015-01-11 5:10 ` Ray Andrews
2015-01-12 9:17 ` Vincent Lefevre
2015-01-12 16:18 ` ZyX
2015-01-13 16:00 ` Vincent Lefevre
2015-01-13 23:03 ` ZyX
2015-01-14 14:47 ` Vincent Lefevre
2015-01-14 21:37 ` ZyX
2015-01-15 13:34 ` Vincent Lefevre
2015-01-15 13:41 ` Vincent Lefevre
2015-01-15 18:32 ` ZyX
2015-01-15 21:57 ` Bart Schaefer
2015-01-09 22:40 ` Peter Stephenson [this message]
2015-01-12 10:55 ` Peter Stephenson
2015-01-14 15:02 ` Vincent Lefevre
2015-01-14 15:38 ` Peter Stephenson
2015-01-15 14:58 ` Peter Stephenson
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