Re^2: Blessing interior hashes

in reply to Re: Blessing interior hashes
in thread Blessing interior hashes

Thanks, ikegami. I'll use that.

I was initially puzzled—what is going inside those eval's? Let me see if I've puzzled it out right:

If $ref is a reference to a hash, then %$ref will eval to something legal.
- It's possibly an empty hash.
- The '|| 1' assures a true value.
If $ref is not a reference to a hash or something that can be used as a hash, then
- an error occurs.
- eval returns undef.
- $@ would contain an error message if we checked it (but we don't because the undef told us all we need to know.)

Right?

throop

Comment on Re^2: Blessing interior hashes

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Re^3: Blessing interior hashes by ikegami (Patriarch) on Oct 03, 2007 at 18:28 UTC
Yup, excellent! Two little additions: `\|\| 1` assures a true value when `%$ref` is an empty hash. `\|\| 1` avoids the "void context" warning `; 1` would issue. One little correction: On error, `eval` returns false (dualvar 0, ""), not undef.	[reply] [d/l] [select]
Re^4: Blessing interior hashes by lodin (Hermit) on Oct 03, 2007 at 19:07 UTC
On error, eval returns false (dualvar 0, ""), not undef. From perlfunc: If there is a syntax error or runtime error, or a `die` statement is executed, an undefined value is returned by `eval` lodin	[reply] [d/l] [select]
Re^5: Blessing interior hashes by ikegami (Patriarch) on Oct 03, 2007 at 19:51 UTC
I had tested with the following. Note the lack of warning `>perl -wle"$r=[]; print eval { %$r \|\| 1 }` [download] Turns out we're both wrong. `eval` returns an empty list. `>perl -wle"$r=[]; print scalar(() = eval { %$r \|\| 1 }); 0` [download] An empty list is interpreted as undef in scalar context.	[reply] [d/l] [select]
Re^6: Blessing interior hashes by lodin (Hermit) on Oct 03, 2007 at 20:24 UTC
Re^7: Blessing interior hashes by ikegami (Patriarch) on Oct 03, 2007 at 20:37 UTC

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