Re: blocks in Lua (was Re: [PROPOSAL] [PATCH] simple method call)

[Tom N Harris <whoopdedo@...>]

On Saturday, June 13, 2015 07:53:59 AM Jay Carlson wrote:
> This is the spot where I suggest Lua get blocks:
> 
> commands:foreach() in cmd do
>    print(cmd)
> end
> 
> Where "foreach" looks like:
> 
> function foreach(l)
>   for _,v in ipairs(l) do
>     goto in(v)
>   end
> end
> 
> Where "goto in()" is like a function call to the block parameter.
> 
> The block has no name. "goto in()" is special syntax like "…". There is no
> way for the callee to capture the block, and it is safe to allocate on the
> stack.

There's a whole lot of magic in what you describe, like the mysteriously 
scoped "in" function that isn't a function.

What you're doing is essentially

    function foreach(l,f) for _,v in ipairs(l) do f(v) end end
    commands:foreach(print)
    -- or rather
    commands:foreach(function(v)
        dosomething(v)
    end)

So following the shorthand "" and {} call with string/table syntax, how about 
a shorthand call with function syntax

    args ::= '(' [explist] ')'
         | tableconstructor
         | LiteralString 
         | functiondef
    functioncall ::= prefixexp args

and thus

    commands:foreach function(v)
        dosomething(v)
    end

Then again, PUC-Rio is just as likely to remove shorthand functioncall syntax 
as add any new ones. It's just a minor matter of convenience that doesn't 
change the expressibility of the language significantly.

-- 
tom <telliamed@whoopdedo.org>