On Friday, 24 October 2014 at 23:20:02 UTC, ketmar via
Digitalmars-d-learn wrote:
On Fri, 24 Oct 2014 22:32:57 +0000
uri via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
wrote:
Hi All,
I was wondering why in the code below f1() works but f2
template version called in the same manner does not. Is there
a good reason from a language/compiler perspective?
Thanks.
uri
---
auto f1(int[2][2] m)
{
return m[0][0]*m[1][1]-m[0][1]*m[1][0];
}
auto f2(T)(T[2][2] m)
{
return m[0][0]*m[1][1]-m[0][1]*m[1][0];
}
void main()
{
auto res = f1( [[1,2],[3,4]]); // works
assert(res == -2);
res = f2([[1,2],[3,4]]); // deos not work
}
Calling f2() as done above gives the following error:
Error: cannot deduce function from argument types
!()(int[][]), candidates are:
f2(T)(T[2][2] m)
by the way, this will work too:
int[2][2] v = [[1,2],[3,4]];
res = f2(v);
'cause 'v' has correct type, and initializing 'v' does 'magic
casting'.
Thanks for replying.
I think it should work because there's no ambiguity. I now have
to uglify my code and make it !@safe or create a temporary.
I also noticed this when trying things out:
auto f2(T)(int[2][2] m) // Same error as above
auto f2()(int[2][2] m) // Works as per non-template function
On a related note, does the D spec guarantee the following will
be rectangular in memory?
auto a = [ [1,2],[3,4] ];
Cheers,
uri
