This totally makes sense in mksh only.
$ i=4+4; echo $i
This is an assignment of the string "4+4" to the variable i. The string
is then, between assignment and storage, parsed as an arithmetic
expression, because i is of integer type. The expression is calculated
and the result stored.
$ i=i+1; echo $i
This is an assignment of the string "i+1" to the variable i. The string
is then, between assignment and storage, parsed as an arithmetic
expression, because i is of integer type. The expression is calculated
and the result stored.
This works because i=anything, if i is integer, is precisely the same as
i=$((anything)).
$ i+=1; echo $i
This is an assignment of the string “${i}1” to the variable i. The
string is first expanded as "11", then evaluated as an arithmetic
expression, and the result (the number 10#11) stored. This is the same
as: i=$((${i}1)).
“var+=text” is the same as “var=${var}text”. This is the basic tenet,
and this is the thing that will not change. (I am now decided.) The
other mentioned shells do this wrong. (This is one thing I will not
budge for cross-shell consistency.)
It’s much easier to accidentally introduce an error with += forgetting
that the target variable is integer (the integer flag may even have been
set by a caller!) than not using proper integer arithmetics.
Just write one of these:
$ let i+=1; echo $i
$ (( i += 1 )); echo $i
$ (( ++i )); echo $i
$ echo $((i+=1))
These should work the same in all shells mentioned.
At that: if a *caller* passes you an integer variable, in all other
shells you cannot use “+=”, which means you cannot use “+=” in the other
shells reliably at all.
function strconcat {
nameref _strconcat_tgt=$1
_strconcat_tgt+=$2
}
typeset -i foo=1
strconcat foo 2
Bam!
--
You received this bug notification because you are a member of mksh
Mailing List, which is subscribed to mksh.
Matching subscriptions: mkshlist-to-mksh-bugmail
https://bugs.launchpad.net/bugs/1857702
Title:
" +=" operator does string concatenation for integer variables
Status in mksh:
Fix Committed
Bug description:
consider
typeset -i x=0; x+=1; echo $x # → 1 (as in ksh/bash/zsh)
but
typeset -i x=1; x+=1; echo $x # → 11 (rather than 2 as in the other
shells)
I believe mksh should honour the integer declaration and interpret
`+=' accordingly. currently, it does not even consistently use string
concatentation (since the first example does not yield `01' ...).
To manage notifications about this bug go to:
https://bugs.launchpad.net/mksh/+bug/1857702/+subscriptions
