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From: Stephane CHAZELAS on 11 Aug 2010 16:28
2010-08-9, 15:20(+00), Kenny McCormack:
> i=+1
> let I=1?I$i:$i ; echo $I
>
> works and displays 1 (and running the last line again displays 2, and so on)
>
> Now, note that:
>
> [[ $i == +* ]] && echo hi
>
> does the expected thing (displays hi).
>
> But what I want is (for what should be obvious reasons; if they are not,
> let me know)
>
> let I=[[ $i == +* ]]?I$i:$i ; echo $I
>
> But this generates the usual syntax errors. What is the right syntax?

If you'd rather have illegible code:

[[ $i = +* ]]
let "I=$??$i:I$i"

or

let "I=${I#${i##[!+]*}"$I"}$i"

--
Stephane
From: Stephane CHAZELAS on 11 Aug 2010 16:32
2010-08-9, 20:03(+00), Kenny McCormack:
> In article <slrni60l6p.ds5.stephane.chazelas(a)spam.is.invalid>,
> Stephane CHAZELAS <stephane_chazelas(a)yahoo.fr> wrote:
> ...
>>One thing to bear in mind is that "let" is just a command, so
>>it's parsed like any other command. Moreover it's not standard.
>
> Did I not put the word "bash" in the subject line?

Oh, you meant "bash" as in "recent enough versions of bash and
hopefully future versions as well"?

[...]
>>case $i in
>> (+*) I=$(($I$i));;
>> (*) I=$i;;
>>esac
>
> Yes, of course, anyone could do it with "case", but I wanted to use the
> new fancy syntax. That's the whole point.

I suppose "let" existed in ksh long before $((...)) was added to
POSIX. If you want something /new/ and non-standard, use
((...)). If you want something bash-specific, you can always use
$[...] (though zsh eventually added it as well).

--
Stephane
From: Kenny McCormack on 11 Aug 2010 17:58
In article <slrni66203.lo.stephane.chazelas(a)spam.is.invalid>,
Stephane CHAZELAS <stephane_chazelas(a)yahoo.fr> suggested these
possibilities:
....
>[[ $i = +* ]]
>let "I=$??$i:I$i"
>
>or
>
>let "I=${I#${i##[!+]*}"$I"}$i"

Good! Thanks. I knew you could do it.

--
"We should always be disposed to believe that which appears to us to be
white is really black, if the hierarchy of the church so decides."

- Saint Ignatius Loyola (1491-1556) Founder of the Jesuit Order -

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