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From: Bart Schaefer <schaefer@brasslantern.com>
To: Daniel Shahaf <d.s@daniel.shahaf.name>
Cc: Nikolaus Thiel <klt@fsfe.org>,
	"zsh-workers@zsh.org" <zsh-workers@zsh.org>
Subject: Re: zmathfunc: min, max, sum throw error if result equals 0
Date: Sun, 7 Mar 2021 13:39:52 -0800	[thread overview]
Message-ID: <CAH+w=7bPz5u9-mQPbmPmbo=8Cz8em7JmbSn-sp8eZzuvFW3mnQ@mail.gmail.com> (raw)
In-Reply-To: <20210307171712.GA9936@tarpaulin.shahaf.local2>

On Sun, Mar 7, 2021 at 9:17 AM Daniel Shahaf <d.s@daniel.shahaf.name> wrote:
>
> Nikolaus Thiel wrote on Sun, Mar 07, 2021 at 17:37:09 +0100:
> >
> > When the result of min, max or sum equals 0, the functions throw an error.

I would not equate "return nozero" with "throw an error", FWIW.

> Ouch.  Patch series attached.

I think your regression tests cover this, but use of "true" avoids
changing the result in "functions -M" context, correct?

Is it worth testing invalid cases?  Such as uses outside math context
where the arguments are not syntax checked?

As long as we're on the subject:

zsh_math_func_min() {
  local result=$1
  shift
  local arg
  for arg ; do
    (( $arg < result )) && result=$arg
  done
  (( result ))
  true # Careful here: `return 0` evaluates an arithmetic expression
}

Because of the way math context works, if any of $@ is a string that
can be interpreted as a math expression, the above will evaluate it at
least twice (and up to $# times in the case of $1).  This could have
side-effects.

zsh_math_func_min() {
  local result=$(( $1 ))
  shift
  local arg n
  for arg ; do
    (( n = arg )) # evaluate arg exactly once
    (( n < result && (result = n) ))
  done
  (( result ))
  true # Careful here: `return 0` evaluates an arithmetic expression
}


  reply	other threads:[~2021-03-07 21:40 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-07 16:37 Nikolaus Thiel
2021-03-07 17:17 ` Daniel Shahaf
2021-03-07 21:39   ` Bart Schaefer [this message]
2021-03-07 21:56     ` Daniel Shahaf
2021-03-08  2:25       ` Bart Schaefer
2021-04-16 18:26         ` Daniel Shahaf
2021-04-16 18:47           ` Bart Schaefer
2021-04-16 19:50         ` Daniel Shahaf
2021-04-16 20:05           ` Bart Schaefer
2021-04-16 20:08             ` Daniel Shahaf
2021-04-16 18:21   ` Daniel Shahaf
2021-05-16 14:54     ` Lawrence Velázquez
2021-05-18  2:02       ` Daniel Shahaf

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