• Nikhil Jacob (5/5) Dec 12 2016 In the D spec for pure functions it says that a pure function can
• Nicholas Wilson (21/26) Dec 12 2016 what this means is
• Nikhil Jacob (5/34) Dec 12 2016 I mistook the original statement to mean that an impure function
• Nicholas Wilson (3/7) Dec 12 2016 Yeah you can't do that, except in a debug statement. You can

Nikhil Jacob <nikhiljaco gmail.com> writes:

In the D spec for pure functions it says that a pure function can 
override

"can override an impure function, but an impure function cannot 
override a pure one"

Can anyone help me how to do this ?

Nicholas Wilson <iamthewilsonator hotmail.com> writes:

On Tuesday, 13 December 2016 at 04:48:11 UTC, Nikhil Jacob wrote:
 In the D spec for pure functions it says that a pure function 
 can override

 "can override an impure function, but an impure function cannot 
 override a pure one"

 Can anyone help me how to do this ?

what this means is

class Foo
{
    void foo() { ... }
}

class Bar : Foo
{
     override void foo() pure { ... }
}

is allowed. but

int someglobal;
class Foo
{
    void foo() pure { ... }
}

class Bar : Foo
{
     override void foo()  { someglobal = 42; }
}

in not.

Nikhil Jacob <nikhiljaco gmail.com> writes:

On Tuesday, 13 December 2016 at 05:10:02 UTC, Nicholas Wilson 
wrote:
 On Tuesday, 13 December 2016 at 04:48:11 UTC, Nikhil Jacob 
 wrote:
 In the D spec for pure functions it says that a pure function 
 can override

 "can override an impure function, but an impure function 
 cannot override a pure one"

 Can anyone help me how to do this ?

 what this means is

 class Foo
 {
    void foo() { ... }
 }

 class Bar : Foo
 {
     override void foo() pure { ... }
 }

 is allowed. but

 int someglobal;
 class Foo
 {
    void foo() pure { ... }
 }

 class Bar : Foo
 {
     override void foo()  { someglobal = 42; }
 }

 in not.

I mistook the original statement to mean that an impure function 
can be called from a pure function with some manual overrides.

Thank you for the clarification.

Nicholas Wilson <iamthewilsonator hotmail.com> writes:

On Tuesday, 13 December 2016 at 05:13:01 UTC, Nikhil Jacob wrote:
 I mistook the original statement to mean that an impure 
 function can be called from a pure function with some manual 
 overrides.

 Thank you for the clarification.

Yeah you can't do that, except in a debug statement. You can 
however cheat with SetFunctionAttributes (from std.traits).