Re: How to disable assigning a value to a property?
On Tuesday, 6 July 2021 at 10:06:11 UTC, Jack Applegame wrote:
Here's another way using ``` std.typecons ```
```d
import std.stdio;
import std.typecons;
alias input = Typedef!int; //new code
struct Field {
void opAssign(int a) {
writefln("Field.opAssign(%s)", a);
}
}
struct Register {
Field clock(input a) {
writefln("Register.clock(%s)", cast(int)a); //note the
cast
return Field();
}
}
void main() {
input ip = 1;
Register register;
register.clock(ip) = 10; // works, good
//register.clock = 10;// works too, how to disable it?
EDIT: Now it doesn't work :)
}
```
You will have to either cast your literal, or provide a variable
with the new type as input though, so it is also not perfect.
Re: How to disable assigning a value to a property?
On Tuesday, 6 July 2021 at 15:24:37 UTC, jfondren wrote:
3. https://run.dlang.io/is/AJM6Vg - hybrid where ClockAssign
has an unsafe pointer that the compiler complains about :/
4.
```d
import std.stdio;
struct Field {
void opAssign(int a) {
writefln("Field.opAssign(%s)", a);
}
}
struct ClockAssign {
Field[] clocks;
void opIndexAssign(int a, int b) {
writefln("Register.clock(%s)", a);
clocks ~= Field();
clocks[$-1] = b;
}
}
struct Register {
ClockAssign clock;
}
void main() {
Register register;
register.clock[1] = 10;
// register.clock = 10; // error
}
```
Re: How to disable assigning a value to a property?
On Tuesday, 6 July 2021 at 10:06:11 UTC, Jack Applegame wrote:
How to disable `register.clock = 10;` but allow
`register.clock(1) = 10;`?
I want to get a compilation error on `register.clock = 10;`
Some options:
1. return a temporary struct with an opIndex
```d
import std.stdio;
struct Field {
void opAssign(int a) {
writefln("Field.opAssign(%s)", a);
}
}
struct ClockAssign {
Field opIndex(int a) {
writefln("Register.clock(%s)", a);
return Field();
}
}
struct Register {
ClockAssign clock() {
return ClockAssign();
}
}
void main() {
Register register;
register.clock[1] = 10; // works, good
//register.clock = 10; // error
}
```
2. https://run.dlang.io/is/bkV64U - keep track of fields and fail
at runtime if a field was never initialized (because it was
silently discarded in this case).
3. https://run.dlang.io/is/AJM6Vg - hybrid where ClockAssign has
an unsafe pointer that the compiler complains about :/
Re: How to disable assigning a value to a property?
On 7/6/21 9:27 AM, Jack Applegame wrote: On Tuesday, 6 July 2021 at 12:33:20 UTC, Adam D Ruppe wrote: The language always allows `a = b;` to be rewritten as `a(b);`. And that's sad. It should happen for properties only. Yes, I lament that there is no way to control how people call your function. It can result in surprising things, and it means as a library designer you have to consider this usage when picking names. There are a few "draft" DIP proposals (under the old DIP system) here: https://wiki.dlang.org/DIPs But I think the time of being able to make such a disruptive change has passed. For better or worse we have the half-implemented near-useless meaning of `@property`, and basically it's unneeded. -Steve
Re: How to disable assigning a value to a property?
On Tuesday, 6 July 2021 at 13:27:43 UTC, Jack Applegame wrote: And that's sad. It should happen for properties only. Totally disagree. This is one of my favorite D features.
Re: How to disable assigning a value to a property?
On Tuesday, 6 July 2021 at 12:33:20 UTC, Adam D Ruppe wrote: The language always allows `a = b;` to be rewritten as `a(b);`. And that's sad. It should happen for properties only.
Re: How to disable assigning a value to a property?
On Tuesday, 6 July 2021 at 10:06:11 UTC, Jack Applegame wrote:
How to disable `register.clock = 10;`
You don't. The language always allows `a = b;` to be rewritten as
`a(b);`.
Best you can do is use different types for the two arguments.
Maybe clock could take a struct Clock { int x; } or something
instead.
Re: How to disable assigning a value to a property?
On Tuesday, 6 July 2021 at 10:25:28 UTC, Dennis wrote: We're [still awaiting formal assessment on dip1038](https://forum.dlang.org/thread/sojvxakgruzfvbigz...@forum.dlang.org), but if that gets in, you can mark `clock` or `Field` `@nodicard`. Otherwise I don't know of a way. Yes, it would help.
Re: How to disable assigning a value to a property?
On Tuesday, 6 July 2021 at 10:06:11 UTC, Jack Applegame wrote: How to disable `register.clock = 10;` but allow `register.clock(1) = 10;`? I want to get a compilation error on `register.clock = 10;` We're [still awaiting formal assessment on dip1038](https://forum.dlang.org/thread/sojvxakgruzfvbigz...@forum.dlang.org), but if that gets in, you can mark `clock` or `Field` `@nodicard`. Otherwise I don't know of a way.
Re: How to disable assigning a value to a property?
On Tuesday, 6 July 2021 at 10:24:45 UTC, drug wrote: Something like using different types for arguments in `Register.clock` and `Field.opAssign`? I've been thinking about it. Unfortunately, this is not always convenient.
Re: How to disable assigning a value to a property?
06.07.2021 13:06, Jack Applegame пишет:
Code:
```d
import std.stdio;
struct Field {
void opAssign(int a) {
writefln("Field.opAssign(%s)", a);
}
}
struct Register {
Field clock(int a) {
writefln("Register.clock(%s)", a);
return Field();
}
}
void main() {
Register register;
register.clock(1) = 10; // works, good
register.clock = 10; // works too, how to disable it?
}
```
How to disable `register.clock = 10;` but allow `register.clock(1) = 10;`?
I want to get a compilation error on `register.clock = 10;`
Something like using different types for arguments in `Register.clock`
and `Field.opAssign`?
How to disable assigning a value to a property?
Code:
```d
import std.stdio;
struct Field {
void opAssign(int a) {
writefln("Field.opAssign(%s)", a);
}
}
struct Register {
Field clock(int a) {
writefln("Register.clock(%s)", a);
return Field();
}
}
void main() {
Register register;
register.clock(1) = 10; // works, good
register.clock = 10;// works too, how to disable it?
}
```
How to disable `register.clock = 10;` but allow
`register.clock(1) = 10;`?
I want to get a compilation error on `register.clock = 10;`
