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Function object.opEquals
Returns true if lhs and rhs are equal.
Example
If aliased to the same object or both null => equal
class F { int flag; this(int flag) { this .flag = flag; } }
F f;
assert(f == f); // both null
f = new F(1);
assert(f == f); // both aliased to the same object
Example
If either is null => non-equal
class F { int flag; this(int flag) { this .flag = flag; } }
F f;
assert(!(new F(0) == f));
assert(!(f == new F(0)));
Example
If same exact type => one call to method opEquals
class F
{
int flag;
this(int flag)
{
this .flag = flag;
}
override bool opEquals(const Object o)
{
return flag == (cast(F) o) .flag;
}
}
F f;
writeln(new F(0)); // new F(0)
assert(!(new F(0) == new F(1)));
Example
General case => symmetric calls to method opEquals
int fEquals, gEquals;
class Base
{
int flag;
this(int flag)
{
this .flag = flag;
}
}
class F : Base
{
this(int flag) { super(flag); }
override bool opEquals(const Object o)
{
fEquals++;
return flag == (cast(Base) o) .flag;
}
}
class G : Base
{
this(int flag) { super(flag); }
override bool opEquals(const Object o)
{
gEquals++;
return flag == (cast(Base) o) .flag;
}
}
writeln(new F(1)); // new G(1)
writeln(fEquals); // 1
writeln(gEquals); // 1
Authors
Walter Bright, Sean Kelly
License
Copyright © 1999-2022 by the D Language Foundation | Page generated by ddox.