Re: goto in expressions

[Sean Conner <sean@...>]

It was thus said that the Great Andrew Starks once stated:
> On Tue, Dec 16, 2014 at 1:57 PM, Sean Conner <sean@conman.org> wrote:
> >   -spc (Is my narrative good enough?)
> 
> The basics of your answer were known to me, but the details are helpful.
> 
> I was thinking of this in a way that is related to something else that
> I do, all of the time:
> 
> ```
> local x = x or error("You must have a value for x!")
> ```

  [ snip ]

> I see that in the case of `error`, the rule regarding bare expressions
> is not broken. I'm hoping for the same thing with `goto`, except I
> acknowledge that it's an expression.

  That's because error() is a function, and a function call is permitted in
an expression, since a function can return a value to be used in an
expression.  The Lua compiler doesn't know that error() doesn't return (nor
do I think it cares, since even a function that doesn't return anything also
returns an infinite number of nils [1]).

> Also, this logically begs the question, if this were legal,
> could/would this also be legal:
> 
> ```
> x = x or return nil
> ```
> 
> Maybe this is just a fundamentally bad idea? That is: "good code
> doesn't do this."

  I'll reserve judgement on that question, but will respond with this one:
What should be printed in the following hypothetical code?

	x = 1	-- create global X
	y = 2	-- create global Y

	function foo()
	  x = 3 + return 4
	end

	function bar()
	  y = return 4 + 3
	end

	a = foo()
	b = bar()

	print("a",a)
	print("b",b)
	print("x",x)
	print("y",y)

  -spc (It's not a question of "no one will ever do this" but "this WILL
	come to pass ... ")

[1]	In the same way a turned-off computer produces vast amounts of
	nothing really fast.