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[An ongoing series of "don't repeat yourself" peeves.]

On Mar 23, 2014 9:50 AM, "Roberto Ierusalimschy" <> wrote:

> The traditional method is this:
>   local buffer = {}  -- create a buffer
>   buffer[#buffer + 1] = x    -- add values

LambdaMOO[1] has sugar for this:

buffer[# + 1] = x

in which # is shorthand for length() of the innermost subscripted _expression_. Since MOO lists are immutable and length() cannot be overriden, the semantics can be fuzzy. For Lua it would be something like

local tmp = buffer
tmp[#tmp + 1] = x

and in general calling apply('#', tmp) every place a 0-ary # is encountered. We already evaluated the object to be indexed, so tmp is on the stack I think. Anyway

buffer[#] = nil

is the other idiom. More generally, this allows addressing from the end of the array, filling the same niche negative index values do in the stack API.

I note with some amusement that #-1 is stack -2 and #-0 is stack -1.


[1]: It's actually buffer[$] in MOO. The syntax "#1234" is a literal for an objnum, a reference to an object. The system object, #0, has a bunch of special functions; one is as a registry of public identifiers. "$foo" is sugar for "".