`$_` is not reserved for `list()` and `foreach`

[fredemmott]

It's frequently used for them, but is not reserved; it can be used for any mandatory-but-unused assignment.

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[fredemmott]

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[AndrewDiMola]

@fredemmott - Was thinking about adding actual examples to make it more useful.

Do these examples convey what you're trying to teach?

$tuple = tuple('H', 'a', 'c', 'k', 'l', 'a', 'n', 'g');

// create names for $a, $b, $c, and $d, but ignore everything else
list($a, $b, $c, $d, $_, $_, $_, $_) = $tuple;
echo("I love ".$a.$b.$c.$d); // "I love Hack"

$keyed_container = dict['H' => 8, 'a' => 1, 'c' => 3, 'k' => 11];

// use the placeholder variable for keys instead of values
foreach ($keyed_container as $key => $_) {
  echo ($key); // prints keys: 'Hack'
}

echo(" ... and associated values: ");

// a regular example for contrast
foreach ($keyed_container as $key) {
  echo ($key); // prints values: 81311
}

[fredemmott]

The for-each example does; the tuple example technically does, however:

• it's showing using a tuple as a vec, which is a bit of a smell; while it's tangental, it'd be better not to include it
• I feel that skipping an element in the middle of a tuple is a clearer example

[fredemmott]

foreach ($keyed_container as $key) {

Also that should be $value, not $key

[edwinsmith]

Hi Fred!

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[fredemmott]

@AndrewDiMola would you like me to change these to full examples, or is that a follow-up you'd like to do?

what you're trying to teach

The main thing I want to do with this PR is to remove "is reserved for use in the list intrinsic function and the foreach statement"; just added some examples in passing while I was here to hopefully make 'why does this exist?' clearer :)

[AndrewDiMola]

@AndrewDiMola would you like me to change these to full examples, or is that a follow-up you'd like to do?

what you're trying to teach

The main thing I want to do with this PR is to remove "is reserved for use in the list intrinsic function and the foreach statement"; just added some examples in passing while I was here to hopefully make 'why does this exist?' clearer :)

We can merge and then I'll add improvements in a separate PR (maybe just for the foreach). Sorry for the delay! In Hack on Hack this week!