Re: Another example for syntactically lightweight closures

[Asko Kauppi <askok@...>]

Did a 'lambda' mod that follows the syntax in MetaLua, with one  
extension.
Blocks, not only expressions can be used within the body.

local t=
    { add= |a,b| a+b,
      sub= |a,b| a-b,

      -- Blocks can be used when wrapped in some scope-declaring  
construct,
      -- s.a. 'if-then-else-end', 'for..end', 'do..end'

      --side_effect= || c= c+1,   -- not ok (comma implies more  
values, not end of assignment)
      side_effect= || do c=c+1 end,   --ok
      side_effect2= || if c>0 then c=c+1 else c=c-1 end,
      side_effect3= || for i=1,99 do c=c*i end,

      z= |a| if a>0 then =a+1 else =a-1 end,
    }

This should be as keyword-scarce as can get, and actually I like it.

-asko


Asko Kauppi kirjoitti 7.2.2008 kello 9:24:

> What would you think of a notation like this?
>
> {
> 	yyy=	do =something end
> 	xxx= 	do(a,b) =a+b end
> 	zzz= 	do(a,b,c) if a then =b else =c end end
> }
>
> Will make it a luaSub mod for trial, but thought of asking opinions  
> first.
>
> do ... end	->  	function() ... end
> do(...) ... end	->	function(...) ... end
>
> = exp		->	return exp		(within the enclosed block)
>
> Especially the '=' trick is handy, since it makes simple closures  
> readable and does not (is this true?) overlap with existing valid  
> Lua syntax.
>
> -asko
>
>
> David Manura kirjoitti 7.2.2008 kello 4:30:
>
> > Miles Bader writes:
> > > Bret Victor writes:
> > > > I thing I like about Lua syntax is that punctuation is kept  
> > > > minimal,
> > > > and words are used (in, do, end) when that's how you would read the
> > > > code out loud.
> > >
> > > I agree, in general -- I don't dislike punctuation heavy  
> > > languages like
> > > C, but Lua has a consistent and attractive style of its own.   
> > > [Still, in
> > > the middle of an expression, I think a punctuation-oriented lambda
> > > syntax isn't out of place, even in Lua.]
> >
> > In Lua, we do write "{1,2}" rather than "table 1, 2 end".  Given  
> > that functions
> > are fundamental data type, like tables, there is consistency in using
> > punctuation to denote functions, particularly when used as lambda  
> > expressions.
> >
> > Approaches for syntactically lightweight closures are also  
> > discussed in [1].
> >
> > [1] http://lua-users.org/wiki/ShortAnonymousFunctions