* Documentation for code execution in substitutions using patterns
@ 2017-10-17 7:01 Sebastian Gniazdowski
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From: Sebastian Gniazdowski @ 2017-10-17 7:01 UTC (permalink / raw)
To: zsh-workers
Hello,
Zsh has very flexible substitutions. So flexible that I was able to write ZUI library, and if I was to port it to e.g. python, it would be probably hard if not impossible. But I think the most powerful part – code execution – isn't documented and isn't always active. For example:
% local -A map=( a 1 b 2 ); str="abc"; echo "${str//(#m)?/${map[$MATCH]}}"
12
% unsetopt extendedglob
% local -A map=( a 1 b 2 ); str="abc"; echo "${str//(#m)?/${map[$MATCH]}}"
abc
If (#m) alone (without e-glob) could do code execution then a more minimalistic code could be written (no need for localoptions extendedglob). Other example:
% line=0; arr=( a b c d ); echo ${arr[@]//(#b)(*)/$(( ++line ))}
1 2 3 4
% line=0; arr=( a b c d ); echo ${arr[@]//(#b)*/$(( ++ line ))}
1 1 1 1
(#b) needs extendedglob so no additional variations here. One more less-meaningful substitution:
% line=0; arr=( a b c d ); echo ${arr[@]//(*)/$(( ++ line ))}
1 1 1 1
Maybe there's something more on this topic? These nuances could be documented after explaining why above variations exist?
--
Sebastian Gniazdowski
psprint /at/ zdharma.org
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