On 6/29/13 7:30 PM, Walter Bright wrote:
On 6/29/2013 2:53 PM, Ary Borenszweig wrote:
On 6/29/13 6:01 PM, Walter Bright wrote:
On 6/29/2013 12:18 PM, Ary Borenszweig wrote:
What you are asking is essentially what Crystal does for all variables
(and types):
https://github.com/manastech/crystal/wiki/Introduction#type-inference
Your example would be written like this:
x = 3
y = f()
x = 3.9
But since Crystal transforms your code to SSA
(http://en.wikipedia.org/wiki/Static_single_assignment_form) you
actually have
*two* "x" variables in your code. The first one is of type Int32, the
second of
type Float64.
Sorry, but that seems like a solution in search of a problem.
And besides, yuk. Imagine the bugs caused by "hey, it doesn't implicitly
convert, so instead of letting the user know he goofed, let's just
silently create a new variable!"
Sorry, but I can't imagine those bugs. Can you show me an example?
Sure:
x = 3
px = &x
y = f()
x = 3.9
// uh-oh, *px points to a different x, and wasn't updated!
printf("%d\n", x); // uh-oh, I thought x was an int!
If the last statements were:
x = 4
printf("%d\n", *px);
I can see where the problem is (you would expect that to print 4,
right?). That can be easily fixed by not transforming the last x to SSA
if its address is taken.
That's a really good example you gave :-)
