On Sun, Apr 23, 2017 at 3:25 PM, Florian Mayer <mayerflor...@me.com> wrote: [...] > Why not? Why is it not reasonable to expect an intuitive > result from (())? The most intuitive thing, in my opinion, > would be to use nameref for side effects by default, because in order > to get a value from an id, (()) already follows namerefs.
First, the documented behavior (https://www.gnu.org/software/bash/manual/html_node/Shell-Arithmetic.html#Shell-Arithmetic) is this: | The *value* of a variable is evaluated as an arithmetic expression when it is referenced, | or when a variable which has been given the integer attribute using ‘declare -i’ is | assigned a value (emphasis is mine) Second, every other major shell that implements recursive evaluation of arithmetical expressions behaves the same way as bash: | dualbus@debian:~$ for sh in dash mksh zsh ksh93 posh 'busybox sh' bash; do $sh -c 'a=b b=2; echo $((a++)) $a $b'; done | dash: 1: Illegal number: b | 2 3 2 | 2 3 2 | 2 3 2 | 2 3 2 | 2 3 2 | 2 3 2 | | dualbus@debian:~$ dpkg -l dash mksh zsh ksh posh busybox bash | Desired=Unknown/Install/Remove/Purge/Hold | | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend | |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad) | ||/ Name Version Architecture Description | +++-===========================-==================-==================-============================================================ | ii bash 4.4-4+b1 amd64 GNU Bourne Again SHell | ii busybox 1:1.22.0-19+b2 amd64 Tiny utilities for small and embedded systems | ii dash 0.5.8-2.4 amd64 POSIX-compliant shell | ii ksh 93u+20120801-2+b1 amd64 Real, AT&T version of the Korn shell | ii mksh 54-2+b2 amd64 MirBSD Korn Shell | ii posh 0.12.6+b1 amd64 Policy-compliant Ordinary SHell | ii zsh 5.3.1-4 amd64 shell with lots of features And third, you haven't really made a compelling argument to change this behavior. Doing so will break backwards compatibility, compatibility with other shells that implement this feature, and in my opinion, doesn't help much in making recursive expansion of arithmetical expressions more "intuitive". Why is it so important that this be changed?
