CUM 2: Lists
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Some people claim that strings aren't really convenient enough for all your data structure needs, so Comefrom0x10 should implement lists.

Status of this document
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Draft, not yet accepted by CUP.

Syntax
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Use square brackets, as this matches the state of the art and is unlikely to confuse programmers::

   [item1, item2, etc]

Dereference an item in a list::

   ['a', 'b', 'c']@0 # extract the 'a' value

Even though languages much more commonly use square brackets to extract list items, that syntax is annoying and sure to be obsolete in future languages. The ``@`` syntax only requires typing one character.

This requires some careful consideration of the precedence of ``@``. It probably should be lower than all mathematical operators, for ease of using computed indices without requiring parens.

The ``@`` operator probably should be right-associative. Consider::

   ['a','b']@[1,1,0]@2

Which would be nonsensical with left-associativity.

Naturally, retrieving values at nonexistent indices should be undefined::

   []@2 # undefined

Negative indexing should, of course, be allowed.

Slicing
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Slices should use Python-style half open ranges and the syntax can be quite similar::

   []@start:end:stride

Immutability
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All data types in Cf0x10 are currently immutable, for robustness [#]_. Lists should be no different.

Relationship to strings
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Indexing and slicing should also be implemented for strings.

Prior art
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I think I've seen a language with a single-character list operator, but I can't remember where.

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.. [#] Not that immutability matters, since variables can, um, vary