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2009/12/5 spir <>:
> Can we consider simply wrapping the whole expression inside (...)?
>   function (x,y,z) (x+y*z)
> This avoids the need for both '=' and an 'end' token.
> (I guess "function(...)(...)..." is well a syntax error as of now?)

This is not a syntax error. The following compiles well:
    local f = function(...)(...)(...) end
and can even be run (try f(print)).

On the other hand, I don't think any valid expression or statement can
start with a single square bracket. I'm not sure how to declare the
parameter names, but here are some examples with an infix keyword

local f = [x + y with x, y]
assert([x + y with x, y](3, 4) == 7)
local t3 = map([x + y with x, y], t1, t2)
foreach(t, [x + y with x, y])

A close form could already be implemented, without upvalues though:

local f = y[[ x + y with x, y ]]

One could imagine having the parameter naming be optionnal, and use
for example $1, $2, etc. as default names:

assert([$1 + $2](3, 4) == 7)

But I'm still not convinced adding such a short function form is a good idea.