Am 07.08.2010 14:10, schrieb simendsjo:
I'm new to D2, so please.. :)
The spec on Array Operations,
http://www.digitalmars.com/d/2./arrays.html says:
"""A vector operation is indicated by the slice operator appearing as
the lvalue of an =, +=, -=, *=, /=, %=, ^=, &= or |= operator."""
The following tests works fine as I expected:
{
double[3] a = [1,1,1];
double[3] b;
b[] = a[] + 3;
assert(a == [1,1,1]);
assert(b == [4,4,4]);
}
{
double[3] a = [1,1,1];
auto b = a;
b[] = a[] + 3;
assert(a == [1,1,1]);
assert(b == [4,4,4]);
}
But from here on I'm having problems...
{
double[] a = [1,1,1];
double[] b;
b[] = a[] + 3;
assert(a == [1,1,1]);
assert(b == [4,4,4]); // fails as b.length == 0.. Should the compiler
say something?
}
{
double[] a = [1,1,1];
double[] b;
b.length = a.length;
b[] = a[] + 3;
assert(a == [1,1,1]);
assert(b == [4,4,4]); // Now it's fine
}
{
double[3] a = [1,1,1];
double[3] b = a[] + 3; // works although lvalue isn't a slice. Static
arrays? Because it's an initial value?
assert(a == [1,1,1]);
assert(b == [4,4,4]);
}
{
double[3] a = [1,1,1];
auto b = a;
b = a[] + 3; // And so does this.. Something to do with static arrays?
assert(a == [1,1,1]);
assert(b == [4,4,4]);
}
{ // Like the previous example, but with dynamic arrays..
double[] a = [1,1,1];
auto b = a;
assert(a is b);
b = a[] + 3;
assert(a == [1,1,1]);
//writeln(b); // access violation. Because of dynamic arrays?
}
{ // Like above, but using slicing like the spec says.. Works fine
double[] a = [1,1,1];
auto b = a;
assert(a is b);
writeln(typeof(b).stringof); // double[]
b[] = a[] + 3;
assert(a == [4,4,4]); // a also changed. I expected this
assert(b == [4,4,4]);
}
{
double[3] a = [1,1,1];
auto b = a[] + 3; // What happens here?
writeln(typeof(b).stringof); // double[]
assert(b.length == 3);
assert(b.capacity == 0);
//writeln(b); // access violation
}
{ // Same as above?
double[3] a = [1,1,1];
//writeln(a[] + 3); // access violation
}
Hi,
I don't the answer to all of your problems but what I can say you is:
* D-Arrays are references to structs which point to the data
* An arrayvariable on the left-hand-side of an assignment sets the
reference of this variable. (no copy!)
* An array slice is mostly the same as the array variable itself but if
it's on the left-hand-side of an assignment, the data is copied from the
right-hand-side.
So for example your third example can't work because b is null and so
there's no place you can copy the data to.
