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Date: Thu, 18 Dec 2014 22:45:20 -0500
From: Eric Cook <llua@gmx.com>
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Subject: Could someone clarify how math functions work?
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In the `functions -M' section of zshbuiltins there is the sentence:
"The  result  of the last arithmetical expression evaluated inside the
shell function (even if it is a form that normally only returns a
status) gives the result of the mathematical function."

but:
zsh -c 'add() ( for arg; do (( n += arg )); done; print  n: $n );
functions -M add; print results: $(( add(1,2,3) ))'

Outputs:
n: 6
results: 3

where as:
zsh -c 'add() { local arg n; for arg; do (( n += arg )); done; print n:
$n }; functions -M add; print results: $(( add(1,2,3) ))'

Outputs:
n: 6
results: 6

Is that expected behavior? If so, could you explain why?