Another take on locals by default.
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- Subject: Another take on locals by default.
- From: Pierre-Yves Gérardy <pygy79@...>
- Date: 2012年5月22日 14:55:51 +0200
I just stumbled on LiveScript (http://gkz.github.com/LiveScript/), yet
another CoffeeScript fork.
The language has locals by default, and has an interesting solution to
the local/upvalue definition and assignment conundrum.
`a = 5` is always a local assignment. a is declared as local if it
wasn't already. To assingn to an upvalue, you use the := operator.
The language doesn't have globals. Transposed to Lua, this would be.
make_incr = function()
acc=0 --local, by default
return function()
acc = acc + 1
-- a local acc shadows the upvalue.
-- this always add 1 to nil, or 1 to 0,
-- depending on when you decide to declare the local,
-- before or after the evaluation of the right hand side.
return acc
end
end
incr= make_incr()
incr() --> 1
incr() --> 1
-- This works as intended
make_incr = function()
acc=0 --local, by default
return function()
acc := acc + 1 -- upvalue assignment
return acc
end
end
Marking assignment to non-locals explicit makes IMO the code easier to read.
Globals could use yet another token.
This would prevent a lot of bugs, and make strict.lua obsolete.
If not for Lua, this could be a nice improvement in MoonScript.
Kind regards,
-- Pierre-Yves