On Friday, 1 April 2022 at 22:22:21 UTC, Vijay Nayar wrote:
A `RedBlackTree` constructs and runs perfectly fine using "int"
as the data type, but it seems to blow up as soon as I use
`std.variant : Variant`.
```
Compilation output (1: )
/dlang/dmd/linux/bin64/../../src/phobos/std/container/rbtree.d(1116): Error: `@safe`
function `std.container.rbtree.RedBlackTree!(VariantN!32LU, "a < b",
false).RedBlackTree.toHash` cannot call `@system` function
`std.container.rbtree.RBRange!(RBNode!(VariantN!32LU)*).RBRange.front`
/dlang/dmd/linux/bin64/../../src/phobos/std/container/rbtree.d(682):
`std.container.rbtree.RBRange!(RBNode!(VariantN!32LU)*).RBRange.front` is
declared here
/dlang/dmd/linux/bin64/../../src/phobos/std/container/rbtree.d(1116): Error:
destructor `std.variant.VariantN!32LU.VariantN.~this` is not `nothrow`
/dlang/dmd/linux/bin64/../../src/phobos/std/container/rbtree.d(1113): Error: function
`std.container.rbtree.RedBlackTree!(VariantN!32LU, "a < b",
false).RedBlackTree.toHash` may throw but is marked as `nothrow`
onlineapp.d(10): Error: template instance
`std.container.rbtree.RedBlackTree!(VariantN!32LU, "a < b",
false)` error instantiating
```
If your type includes opCmp() there is no reason not to use
rbTree. Let me give a simple example:
```d
struct Char {
char c;
auto opCmp(Char rhs) const {
return c == rhs.c ? 0: c - rhs.c;
}
}
import std.container.rbtree;
import std.stdio;
void main() {
alias Type = Char;
with(new RedBlackTree!(Type))
{
stableInsert(Type('B'));
stableInsert(Type('A'));
stableInsert(Type('C'));
foreach (v; upperBound(Type('A')))
v.c.write(", ");
writeln; // "B, C, "
}
}
```
SDB@79
