hashMap about functional-php HOT 14 CLOSED

Looks useful! @ajb-in do you have a good idea for a name?

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No good ideas, other than I'd refer to "keys" rather than "hashes" (and would probably reflect that in the name of the argument).
Also, note that this is equivalent to array_combine(map($collection, $callback), $collection)

from functional-php.

Thanks for the feedback! @ajb-in The function is not exactly equivalent to your example because apart from the keys the values can also be mapped in the callback.

>>> hashMap(
...     ['abc', 'foobar'],
...     function ($value) {
...         return [$value[0], strtoupper($value)];
...     }
... )
=> [
     "a" => "ABC",
     "f" => "FOOBAR",
   ]

Your example describes another use case: Mapping only the keys. This would have been sufficient for my needs, even better; Perhaps this is also a useful function? A better name for hashMap could be keyValueMap and your example could be called keyMap.

In comparison:

>>> map(
...     ['abc', 'foobar'],
...     function ($value) {
...         return strtoupper($value);
...     }
... )
=> [
     "ABC",
     "FOOBAR",
   ]
>>> keyMap(
...     ['abc', 'foobar'],
...     function ($value) {
...         return $value[0];
...     }
... )
=> [
     "a" => "abc",
     "f" => "foobar",
   ]
>>> keyValueMap(
...     ['abc', 'foobar'],
...     function ($value) {
...         return [$value[0], strtoupper($value)];
...     }
... )
=> [
     "a" => "ABC",
     "f" => "FOOBAR",
   ]

What do you think?

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@MazeChaZer @ajb-in instead of doing key and value mapping in one sweep, we could have a mapKeys() that does to keys what map does to values.

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@lstrojny Sounds good to me. I like that even better than the keyValueMap approach.

Edit: Just to be clear, I'm talking about mapKeys()

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Are we at a consens here? Should I start implementing/testing/documenting the mapKeys() function?

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I for one would use mapKeys for a different idea (something akin to Haskell's mapKeys).
But then again, I don't have a better name for this one, and can't find a precedent on the literature apart from the Schwartzian transform.

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What about reindex()?

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Sounds good to me

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Ok, I'm starting to work on this, if we find an even better name we can still change it later on.

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Mh, what is supposed to happen if the callback produces duplicate keys? Should an exception be thrown or should later values just overwrite previous values that had the same key? I tend to throw an exception.

from functional-php.

I looked a little further into this. The PHP builtins array_flip() and array_combine() overwrite previous values which had the same key. Furthermore I saw that in this library exceptions are only thrown for invalid arguments. So I guess the first alternative, just overwriting previous values, makes more sense after all.

from functional-php.

+1 on reindex.
Also agree with your dup key resolution.

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Thanks for the discussion

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