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I was browsing the Perl 6 docs on the shift routine and saw this snippet:
Defined as:
multi sub shift(Array:D ) multi method shift(Array:D:)
I know :D means the Array is defined and not Any or Nil, but what's :D:? It's very hard to search for.
This section of the type signature docs contains more examples of the syntax, but does not (as far as I can tell) explain it.
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There are quite a few differences between vitamin D and vitamin D3 but the main difference between them is that vitamin D is a fat-soluble vitamin that regulates calcium and phosphorous levels of the body whereas the vitamin D3 is the natural form of vitamin D produced by the body from sunlight.
Studies have repeatedly shown that vitamin D3 is superior at raising levels of vitamin D in the body. These findings were supported by a recent review of the evidence which found that vitamin D3 supplementation increased vitamin D levels in the body better than vitamin D2.
They are vitamin D2 and vitamin D3. Previous research suggested that vitamin D3 was a better choice than vitamin D2. However, more recent studies show that vitamin D3 and vitamin D2 are fairly equal for bone health.
Vitamin D3 Comes from Animals, Vitamin D2 from PlantsThe two forms of vitamin D differ depending on their food sources. Vitamin D3 is only found in animal-sourced foods, whereas D2 mainly comes from plant sources and fortified foods. Since vitamin D2 is cheaper to produce, it's the most common form in fortified foods.
The invocant of a method gets passed as an implicit first argument. If you want to use an explicit parameter within the signature (eg to add a type smiley like :D or just to give it a more descriptive name), you need to separate it with a : instead of a , from the rest of the parameter list. This is necessary even in case of an empty list so it can be disambiguated from a signature with a regular positional parameter.
Some more information can be found in the design documents.
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