Re: Arithmetic on strings

[Hans Hagen <pragma@...>]

On 13-6-2012 19:14, liam mail wrote:
> On 13 June 2012 17:35, Roberto Ierusalimschy <roberto@inf.puc-rio.br> wrote:
> > Any performance-conscious code that uses
> > coercion in critical pathes deserves what it gets
>
> It could be said anyone that updates to 5.2.* deservers what they get.
>
> So I take it that if coercion is removed then string concatenation
> would use the '+' operator[1] and Lua programmes would become more
> complicated[2] or are these views now outdated?
>
> Liam
>
>
>
> [1] http://www.lua.org/doc/hopl.pdf
> One of the few (and rather minor) innovations in Lua was
> the syntax for string concatenation. The natural ‘+’ operator
> would be ambiguous, because we wanted automatic coercion of strings to
> numbers in arithmetic operations.
>
> [2] http://www.lua.org/semish94.html
> This coercion is useful because it simplifies programs and avoids the
> need for explicit conversion functions.

What precisely are we talking about?

(1)  1 + "2"  (- * / etc)

(2)  1 .. "2"

(3)  concat({1,"2"})

(4)  format("%s",1)

I suppose only in the first case automatic conversion is unwanted? 
Actually I can imagine that a future concat does a tostring if needed so 
that { 1, "2", true } also works.

Hans

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