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- Subject: RE: block return semantic
- From: Tom Wrensch <Thomas.Wrensch@...>
- Date: Wed, 27 Jun 2001 08:50:21 -0600 (MDT)
Could you elaborate on the "all sorts of reasons" for not allowing
if-then-else as an expression rather than just a statement?
I've used a number of languages that have an if-then-else expressions,
where something like this:
return if x = nil then 0 else x end
is allowed. I find it quite useful for handling default values for
uninitialized variables and alternative computations for edge conditions
x = if x > max then x = 0 else x = x + 1 end
What I *don't* know is how if-then-else as an expression my negatively
impact existing Lua programs, performance, or style. I haven't written
enough Lua code to have a good feel for that.
Note that an alternative approach would be to implement a special
expression version of if-then-else such as Java's <cond> ? <exp1> :
- Tom Wrensch
On Wed, 27 Jun 2001, Reuben Thomas wrote:
> > if a < b then return 10 else return 25 end
> > but some are more comfortable with other, more terse forms that are not
> > currently supported in Lua.
> and indeed (if a<b then 5 else 4) allows if...thens to be expressions rather
> than statements. So you could then imagine writing c = if a <b then 5 else 4
> ...ooh, we're nearly at functional programming. However, it's not at all
> obvious this is a good thing to do to Lua, for all sorts of reasons.
> http://sc3d.org/rrt/ | competent, a. underpromoted