foreach over empty list

rovf has asked for the wisdom of the Perl Monks concerning the following question:

I had the following piece of code

foreach () {}
[download]

I was supposed that this would act as a no-op - looping over an empty list and doing nothing - and was only meant as a placeholder where I wanted to put in the "real meat" later. To my surprise, this didn't compile:

syntax error ... near "()"

Why does it reject my empty list? I re-read perlsyn, but didn't find anything which would forbid such a construct.

--
Ronald Fischer <ynnor@mm.st>

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Re: foreach over empty list by BrowserUk (Patriarch) on Jun 06, 2011 at 14:51 UTC
The first set of parens are a required part of the for/foreach syntax, not an empty list. Put an empty list inside them and all is well: `c:\test\xx>perl -we"for () { print; }" syntax error at -e line 1, near "() " Execution of -e aborted due to compilation errors. c:\test\xx>perl -we"for (()) { print; }"` [download] Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l]

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Re: foreach over empty list
by BrowserUk (Patriarch) on Jun 06, 2011 at 14:51 UTC

The first set of parens are a required part of the for/foreach syntax, not an empty list. Put an empty list inside them and all is well:

c:\test\xx>perl -we"for () { print; }"
syntax error at -e line 1, near "() "
Execution of -e aborted due to compilation errors.

c:\test\xx>perl -we"for (()) { print; }"
[download]

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

[reply]
[d/l]