Floating point in the type system
Hi all,
I came across this example, and wondered what your thoughts on it
are:
```
void main(string[] args)
{
struct Foo(float f) {
alias VAL = f;
float getF() {
return f;
}
}
Foo!(float.nan) f;
Foo!(float.nan) f2;
// This will fail at compile time
static assert(f.VAL == f2.VAL);
// This will fail at run time
assert(f.getF() == f2.getF());
// But this is ok
f = f2;
}
```
It seems a little unusual to me.
Robert
Re: Floating point in the type system
On Saturday, 12 September 2015 at 15:49:23 UTC, Atila Neves wrote:
On Saturday, 12 September 2015 at 15:13:27 UTC, Robert wrote:
Hi all,
I came across this example, and wondered what your thoughts on
it are:
```
void main(string[] args)
{
struct Foo(float f) {
alias VAL = f;
float getF() {
return f;
}
}
Foo!(float.nan) f;
Foo!(float.nan) f2;
// This will fail at compile time
static assert(f.VAL == f2.VAL);
// This will fail at run time
assert(f.getF() == f2.getF());
// But this is ok
f = f2;
}
```
It seems a little unusual to me.
Robert
What do think is unusual?
Atila
It's unusual, because `float.nan != float.nan`, so one might
expect that `typeof(Foo!(float.nan) != Foo!(float.nan))`, whereas
this is clearly not the case, even with both the static assert
and runtime assert failing. I'm just curious to understand the
reasoning behind this, whether it's intentional, and whether it
matters at all.
Re: Floating point in the type system
On Saturday, 12 September 2015 at 15:13:27 UTC, Robert wrote: Hi all, I came across this example, and wondered what your thoughts on it are: It seems a little unusual to me. Robert For what it's worth, I was investigating this initially as a discussion about adding type-level values in Rust, and how to handle unusual cases like this. In the process we've managed to break the Idris type system: https://github.com/idris-lang/Idris-dev/issues/2609. There's been quite a lot of interesting discussion about it on the IRC channels for all three languages :) I'd be interested to know how other languages handle this, if anyone knows.
