From: jdh <dhenman@gmail.com>
To: zsh-workers@zsh.org
Subject: Re: Math expression evaluation error?
Date: Fri, 09 Jan 2015 13:40:42 -0800 [thread overview]
Message-ID: <54B04ADA.9050102@gmail.com> (raw)
In-Reply-To: <20150109201552.1304eafe@ntlworld.com>
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."
I apologize if this is in the manual already.
Regards.
On 2015年01月09日 12:15, Peter Stephenson wrote:
> On Fri, 09 Jan 2015 11:46:44 -0800
> jdh <dhenman@gmail.com> wrote:
>> I believe I read that math expression evaluation will convert all
>> calculations in an expression if "any" value in that expression is a
>> real value.
> This isn't the case and wherever this came from needs correcting.
> Please instead read the documentation under ARITHMETIC EVALUATION in the
> zshmisc manual for what actually happens and let us if know if you think
> that is inadequate. The actually phrasing is "Promotion of integer to
> floating point values is performed where necessary". It also refers
> above that to C --- there's an underlying assumption here that the user
> has some idea of the operation of C-like languages, which might of
> course not be the case. "Where necessary" is in general where an
> operator has a floating point number as one argument and an integer as
> another; a C programmer would recognise the use of the word "promotion"
> as implying this, a general user probably not. So the wording could
> probably be improved. Brief and to the point suggestions on this from
> anyone are welcome (long rambles on why anyone doesn't understand it
> may be invigorating for the rambler but are less useful to us as
> developers :-)).
>
> See also the following shell option:
>
> FORCE_FLOAT
> Constants in arithmetic evaluation will be treated as floating
> point even without the use of a decimal point. Integers in any
> base will be converted.
>
> This is most useful in zcalc, which actually has an option for this.
>
> If the option `-f' is set, all numbers are treated as floating
> point, hence for example the expression `3/4' evaluates to 0.75
> rather than 0. Options must appear in separate words.
>
> pws
next prev parent reply other threads:[~2015-01-09 21:40 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 [this message]
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
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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