This topic actually pops up occasionally. FYI, you can also see the following discussions:
https://lists.gnu.org/archive/html/bug-bash/2014-06/msg00003.html https://lists.gnu.org/archive/html/bug-bash/2014-10/msg00154.html https://lists.gnu.org/archive/html/bug-bash/2015-02/msg00066.html 2021年1月8日(金) 18:21 Oğuz <oguzismailuy...@gmail.com>: > `(( assoc[\$key]++ ))' works as usual, but this is not documented as > far as I know, This is explained in the first link above by quoting two sentences in the document, but I agree with you that this is so non-trivial that it's worth explicitly documenting IMHO. > Considering that the following two works, it doesn't make much sense > that `(( assoc[$key]++ ))' doesn't. I think the POSIX expansion order should be applied to, for example, $((assoc[$key]++)). In this case, the arithmetic evaluation of the whole expression should be performed only after $key in $((assoc[$key]++)) is expanded. There is no reason to introduce a different expansion rule of `((...))' from that of `$((...))'. It feels a bit strange to me to expand `$key' in `(( assoc[$key]++ ))' after determining the arithmetic structure thinking the normal expansion order. > It would be better if at least quoting the key by means of parameter > transformation or `printf %q' worked, because these are the first > workarounds that come to mind; This is maybe a good idea. From Bash 5.1, the single quotation is not a subject to the quote removal of `(( ... ))', so we can use the single quotation as a part of the arithmetic expression. We can just introduce the string literal of the form '...' or $'...' in the arithmetic evaluator. -- Koichi
