digitalmars.D.learn - writeln the struct from the alis this Example from the home page
- Martin Tschierschke (31/31) Nov 18 2021 Hello, if you take the example from the home page, with the
- Paul Backus (16/47) Nov 18 2021 You can define a `toString` method, like this:
- Jordan Wilson (3/21) Nov 18 2021 I thought private was to the module/file, not class/struct?
- Steven Schveighoffer (3/25) Nov 18 2021 `writeln` is not in your module.
- Martin Tschierschke (2/20) Nov 19 2021 Thank you, just removing ``private `` and it worked!
Hello, if you take the example from the home page, with the
additional last line:
```d
struct Point
{
private double[2] p;
// Forward all undefined symbols to p
alias p this;
double dot(Point rhs)
{
return p[0] * rhs.p[0] + p[1] * rhs.p[1];
}
}
void main()
{
import std.stdio : writeln;
// Point behaves like a `double[2]` ...
Point p1, p2; p1 = [2, 1], p2 = [1, 1];
assert(p1[$ - 1] == 1);
// ... but with extended functionality
writeln("p1 dot p2 = ", p1.dot(p2));
// additional line:
writeln(p1); // is not possible !
}
```
/usr/include/dmd/phobos/std/format.d(3193): Error: no [] operator
overload for type Point
..
...
How to define, that for Point the same formatting should be used
as for double[2] ?
Nov 18 2021
On Thursday, 18 November 2021 at 13:51:42 UTC, Martin
Tschierschke wrote:
Hello, if you take the example from the home page, with the
additional last line:
```d
struct Point
{
private double[2] p;
// Forward all undefined symbols to p
alias p this;
double dot(Point rhs)
{
return p[0] * rhs.p[0] + p[1] * rhs.p[1];
}
}
void main()
{
import std.stdio : writeln;
// Point behaves like a `double[2]` ...
Point p1, p2; p1 = [2, 1], p2 = [1, 1];
assert(p1[$ - 1] == 1);
// ... but with extended functionality
writeln("p1 dot p2 = ", p1.dot(p2));
// additional line:
writeln(p1); // is not possible !
}
```
/usr/include/dmd/phobos/std/format.d(3193): Error: no []
operator overload for type Point
..
...
How to define, that for Point the same formatting should be
used as for double[2] ?
You can define a `toString` method, like this:
```d
string toString()
{
import std.conv;
return p.to!string;
}
```
You can find more information about `toString` in the
documentation here: https://dlang.org/phobos/std_format_write.html
By the way, the reason your original version does not work is
that `p` is `private`, so `writeln` cannot access it. If you
change `p` to be `public`, it will work without a `toString`
method.
Nov 18 2021
On Thursday, 18 November 2021 at 16:08:22 UTC, Paul Backus wrote:On Thursday, 18 November 2021 at 13:51:42 UTC, Martin Tschierschke wrote:I thought private was to the module/file, not class/struct? Jordan[...]You can define a `toString` method, like this: ```d string toString() { import std.conv; return p.to!string; } ``` You can find more information about `toString` in the documentation here: https://dlang.org/phobos/std_format_write.html By the way, the reason your original version does not work is that `p` is `private`, so `writeln` cannot access it. If you change `p` to be `public`, it will work without a `toString` method.
Nov 18 2021
Steven Schveighoffer <schveiguy gmail.com> On 11/18/21 2:58 PM, Jordan Wilson wrote:On Thursday, 18 November 2021 at 16:08:22 UTC, Paul Backus wrote:`writeln` is not in your module. -SteveOn Thursday, 18 November 2021 at 13:51:42 UTC, Martin Tschierschke wrote:I thought private was to the module/file, not class/struct?[...]You can define a `toString` method, like this: ```d string toString() { import std.conv; return p.to!string; } ``` You can find more information about `toString` in the documentation here: https://dlang.org/phobos/std_format_write.html By the way, the reason your original version does not work is that `p` is `private`, so `writeln` cannot access it. If you change `p` to be `public`, it will work without a `toString` method.
Nov 18 2021
On Thursday, 18 November 2021 at 16:08:22 UTC, Paul Backus wrote:On Thursday, 18 November 2021 at 13:51:42 UTC, Martin Tschierschke wrote:Thank you, just removing ``private `` and it worked![...]You can define a `toString` method, like this: ```d string toString() { import std.conv; return p.to!string; } ``` You can find more information about `toString` in the documentation here: https://dlang.org/phobos/std_format_write.html By the way, the reason your original version does not work is that `p` is `private`, so `writeln` cannot access it. If you change `p` to be `public`, it will work without a `toString` method.
Nov 19 2021