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digitalmars.D.learn - Declaring constant references in struct members

reply David Zhang <straivers98 gmail.com> writes:
Hi,

Say I have a struct S that holds a reference to an object O. Is 
there a way to express that I want to be able to change the 
reference, but not what the reference points to? Thanks.

struct S {
     O object;
}

class O {
     size_t things.
}
Feb 15
next sibling parent reply Adam D. Ruppe <destructionator gmail.com> writes:
On Thursday, 16 February 2017 at 00:43:30 UTC, David  Zhang wrote:
 struct S {
     O object;
 }
import std.typecons; Rebindable!O object; http://dpldocs.info/experimental-docs/std.typecons.Rebindable.html
Feb 15
parent reply David Zhang <straivers98 gmail.com> writes:
On Thursday, 16 February 2017 at 00:49:45 UTC, Adam D. Ruppe 
wrote:
 On Thursday, 16 February 2017 at 00:43:30 UTC, David  Zhang 
 wrote:
 struct S {
     O object;
 }
import std.typecons; Rebindable!O object; http://dpldocs.info/experimental-docs/std.typecons.Rebindable.html
Is there a similar mechanism for one struct holding another? Otherwise, you get a cannot modify X with immutable members error. eg: struct A { B b; } struct B { const size_t something; } A a = A(B(16)); //attempt to replace a.b with new B a.b = B(32); //error: cannot modify struct a.b B with immutable members
Feb 15
parent Adam D. Ruppe <destructionator gmail.com> writes:
On Thursday, 16 February 2017 at 01:05:58 UTC, David  Zhang wrote:
 Is there a similar mechanism for one struct holding another?
You'd have to make the member a pointer to the struct. immutable(B)* b;
Feb 15
prev sibling parent "H. S. Teoh via Digitalmars-d-learn" <digitalmars-d-learn puremagic.com> writes:
On Thu, Feb 16, 2017 at 12:43:30AM +0000, David Zhang via Digitalmars-d-learn
wrote:
 Hi,
 
 Say I have a struct S that holds a reference to an object O. Is there
 a way to express that I want to be able to change the reference, but
 not what the reference points to? Thanks.
 
 struct S {
     O object;
 }
 
 class O {
     size_t things.
 }
Maybe have a look at std.typecons.Rebindable? T -- What do you call optometrist jokes? Vitreous humor.
Feb 15