Re: How to code a complex AoH?

Hello iatros, and welcome to the Monastery!

Each element of a hash (or of an array, for that matter) must be a scalar value. So if you want to store an array of values in the points slot of a hash, you have to store a pointer to that array:

$student = {
    ...
    points => \@points,
};
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$student = {
    ...
    points => [@points],
};
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See perlreftut and perldsc.

Update: To elaborate on stevieb’s point: if the array @points contains the elements ('a', 'b', 'c', 'd'), then the assignment

$student = {
    ...
    points => @points,
};
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is effectively this:

$student = {
    ...
    'points', 'a',
    'b', 'c',
    'd',
};
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or, equivalently,

$student = {
    ...
    points => 'a',
    b      => 'c',
   'd',
};
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— which explains why the compiler is warning about an odd number of elements in the hash: the last array value ('d') becomes a hash key with no associated value.

Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

Comment on Re: How to code a complex AoH? Select or Download Code

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Re^2: How to code a complex AoH? by haukex (Archbishop) on Mar 25, 2017 at 15:25 UTC
`points => \@points,` Actually, that won't work here - it looks like iatros isn't using strict, or has predeclared `@points` outside of the loop, so that `\@points` and therefore `$$student{points}` will always point to the same array, and that array will get overwritten on each iteration of the loop. `points => [@points],` will work correctly, since it creates a (shallow) copy of the array. (Athanasius, I know you know all this, the explanation is for the benefit of the OP.) iatros: You really should Use strict and warnings, and then use my to declare your variables, including inside the loop: `my ( $id , $gender , $birthday ... ) = ...`. Then you can use both of the code examples that Athanasius showed, because then on each iteration of the loop, `@points` will be a "new" array. Update: Tweaked explanation a tiny bit.	[reply] [d/l] [select]
Re^2: How to code a complex AoH? by AnomalousMonk (Archbishop) on Mar 25, 2017 at 18:01 UTC
... the last array value ... becomes a hash key with no associated value. iatros: Just ~~another~~ \| a minor tweak to Athanasius's otherwise excellent ++explanation: The unpaired key will not have no associated value, but rather the undef value (that's where the `'.5' => undef` in the OPed dump comes from). This, of course, will probably just lead to more warnings down the line! Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re^2: How to code a complex AoH? by iatros (Novice) on Mar 30, 2017 at 17:26 UTC
Thank you for the reply. I hope I've learned my lesson with your help. I will think over the parsing thing. As Larry put it: TIMTOWTDI -HM-	[reply]