Re: How do I make a template function that only accepts instances of a specific class?
On Monday, 18 January 2021 at 19:54:04 UTC, Adam D. Ruppe wrote: On Monday, 18 January 2021 at 19:34:52 UTC, Jack wrote: is that sytax derived from there? sort of. it is the type pattern matching "is expression" described here: https://dlang.org/spec/expression.html#IsExpression I read std.traits and some related stuff but missed reading is expression doc lol The is(A:B) thing technically means "if A is implicitly convertible to B" which of course works for base classes and interfaces well but that's not all it does, like is(int : long) passes too. C# uses something like that too but I totally missed to look for the equivalent in D, which would be pretty much same thing I just remember the syntax thanks to its similarity to type declarations. good way to remember too
Re: How do I make a template function that only accepts instances of a specific class?
On Monday, 18 January 2021 at 19:34:52 UTC, Jack wrote: is that sytax derived from there? sort of. it is the type pattern matching "is expression" described here: https://dlang.org/spec/expression.html#IsExpression The is(A:B) thing technically means "if A is implicitly convertible to B" which of course works for base classes and interfaces well but that's not all it does, like is(int : long) passes too. I just remember the syntax thanks to its similarity to type declarations.
Re: How do I make a template function that only accepts instances of a specific class?
On Monday, 18 January 2021 at 19:02:10 UTC, Adam D. Ruppe wrote:
On Monday, 18 January 2021 at 18:40:37 UTC, Jack wrote:
isInstanceOf from std.traits seems to not work with class the
way I need to. I'd like to make a template function accepts
only class of a specified class type
class A { }
class B : A { }
class C : A { }
int f(T)(in A[int] arr)
Use
if(is(T : A))
the syntax there is similar to the class declaration itself.
is that sytax derived from there?
isInstanceOf is for checking instances of templates rather than
classes.
I see
Thanks!
Re: How do I make a template function that only accepts instances of a specific class?
On Monday, 18 January 2021 at 18:40:37 UTC, Jack wrote:
isInstanceOf from std.traits seems to not work with class the
way I need to. I'd like to make a template function accepts
only class of a specified class type
class A { }
class B : A { }
class C : A { }
int f(T)(in A[int] arr)
Use
if(is(T : A))
the syntax there is similar to the class declaration itself.
isInstanceOf is for checking instances of templates rather than
classes.
How do I make a template function that only accepts instances of a specific class?
isInstanceOf from std.traits seems to not work with class the way
I need to. I'd like to make a template function accepts only
class of a specified class type
class A { }
class B : A { }
class C : A { }
import std.traits : isInstanceOf;
int f(T)(in A[int] arr)
if(isInstanceOf!(A, T)) // doesn't work for class from what I saw
{
foreach(c; arr) {
if((cast(A)c) !is null) {
}
}
// ...
}
int f(T)(in A[int] arr)
if(cast(T) !is null) // run time this is ok but not at compile
time
{
// ...
}
