On 08 Apr 2012, at 01:47, Chet Ramey wrote: > On 4/7/12 4:45 PM, Linda Walsh wrote: >> >> >> >> In modifying some released code on my distro, I ran into the extensive use >> of $[arith] as a means for returning arithmetic evaluations of the >> expression. >> >> I vaguely remember something like that from years ago, but never see any >> reference to >> it -- yet it works, and old code seems to rely on it -- and >> "$[(1+2)/3]" looks cleaner than "$(((1+2)/3))". So what's up with that? > > It dates from Posix circa 1990 (1003.2d9, of which I've lost my paper > copy). I implemented it after the Berkeley guys, mostly Marc > Teitelbaum, put it into Posix. It ended up getting dropped in favor > of the ksh $((...)) expansion, at which point everyone deprecated the > old $[...]. I removed it from the manual sometime later, but it still > works as it always has. > > Chet
Any particular reason for not removing old undocumented functionality, or is that mostly the nature of this beast - dragging along and maintaining ancient code for the sake of compatibility?
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