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Re: Inconsistent arithmetic evaluation of parameters
From: |
Chet Ramey |
Subject: |
Re: Inconsistent arithmetic evaluation of parameters |
Date: |
Wed, 2 Sep 2015 10:23:33 -0400 |
User-agent: |
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 |
On 9/1/15 5:05 PM, Dennis Williamson wrote:
> It's the line above those two where I demonstrate the failure in the
> indirection and equivalency.
>
> $ echo $((foo)) # expansion succeeds, indirection fails
> dash: 4: Illegal number: bar
Because `foo' is expanded, but the value is not treated as an expression.
The dash arithmetic evaluator never treats values resulting from expansion
as expressions, only as constants.
> $ echo $(($foo)) # both expansion and indirection succeed
> 5
Because the arithmetic evaluator sees $(( bar )). The word expansion that
happens before arithmetic evaluation expands $foo.
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_04
is the Posix specification for arithmetic evaluation.
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU chet@case.edu http://cnswww.cns.cwru.edu/~chet/
- Re: Inconsistent arithmetic evaluation of parameters, (continued)
- Re: Inconsistent arithmetic evaluation of parameters, Greg Wooledge, 2015/09/01
- Re: Inconsistent arithmetic evaluation of parameters, Dennis Williamson, 2015/09/01
- Re: Inconsistent arithmetic evaluation of parameters, Andreas Schwab, 2015/09/01
- Re: Inconsistent arithmetic evaluation of parameters, Dennis Williamson, 2015/09/01
- Re: Inconsistent arithmetic evaluation of parameters, Andreas Schwab, 2015/09/02
- Re: Inconsistent arithmetic evaluation of parameters, Dennis Williamson, 2015/09/02
- Re: Inconsistent arithmetic evaluation of parameters, Greg Wooledge, 2015/09/02
- Re: Inconsistent arithmetic evaluation of parameters, Chet Ramey, 2015/09/02
- Re: Inconsistent arithmetic evaluation of parameters, Greg Wooledge, 2015/09/02
- Re: Inconsistent arithmetic evaluation of parameters, Chet Ramey, 2015/09/03
- Re: Inconsistent arithmetic evaluation of parameters,
Chet Ramey <=
- Re: Inconsistent arithmetic evaluation of parameters, Stephane Chazelas, 2015/09/03
- Re: Inconsistent arithmetic evaluation of parameters, Dennis Williamson, 2015/09/03
- Re: Inconsistent arithmetic evaluation of parameters, Chet Ramey, 2015/09/02
Re: Inconsistent arithmetic evaluation of parameters, Chet Ramey, 2015/09/02