Hi,

How do I use a double value in a mixin template that is generating string?

Thanks and Regards
Dibyendu

On Friday, 26 February 2016 at 11:03:43 UTC, Dibyendu Majumdar wrote:
> Hi,
>
> How do I use a double value in a mixin template that is generating string?
>
> Thanks and Regards
> Dibyendu

Have you an example of what's failing right now to show ?

On Friday, 26 February 2016 at 11:07:28 UTC, BBasile wrote:
> On Friday, 26 February 2016 at 11:03:43 UTC, Dibyendu Majumdar wrote:
>> How do I use a double value in a mixin template that is generating string?
>
> Have you an example of what's failing right now to show ?

I am trying something like this:

template MyTAlloc(int n_vars, double v) {
const char[] MyT = "MyT_init(cast(MyT *) alloca(alloc_size(" ~ n_vars ~ ")), " ~ n_vars ~ ", " ~ v ~ ")";
}

MyT *t = mixin(MyTAlloc!(2,5.0));

Error: incompatible types for (("MyT_init(cast(MyT *) alloca(alloc_size(" ~ cast(immutable(char))2 ~ ")), " ~ cast(immutable(char))2 ~ ", ") ~ (5.00000)): 'string' and 'double'

On Friday, 26 February 2016 at 11:13:08 UTC, Dibyendu Majumdar wrote:
> I am trying something like this:
>
> template MyTAlloc(int n_vars, double v) {
> const char[] MyT = "MyT_init(cast(MyT *) alloca(alloc_size(" ~ n_vars ~ ")), " ~ n_vars ~ ", " ~ v ~ ")";

No you cannot because you would have to convert the values to string using std.conv.to or std.format.format(), but they don't work at compile time (see https://issues.dlang.org/show_bug.cgi?id=13568).

Ideally like this:

template MyTAlloc(int n_vars, double v) {
const char[] MyT = "MyT_init(cast(MyT *) alloca(alloc_size(" ~
to!string(n_vars) ~ ")), " ~ to!string(n_vars) ~ ", " ~ to!string(v) ~ ")";

But you can try with regular templates or mixin templates.

On Friday, 26 February 2016 at 11:26:51 UTC, BBasile wrote:
> No you cannot because you would have to convert the values to string using std.conv.to or std.format.format(), but they don't work at compile time (see https://issues.dlang.org/show_bug.cgi?id=13568).

Erratum! Actually you can, example:

import std.stdio;

string foo(double a)()
{
    return "auto value = " ~ a.stringof ~ ";";
}

void main(string[] args)
{
    mixin(foo!0.1);
    writeln(value); // 0.1
    writeln(typeof(value).stringof); // double
}

So you have to use .stringof on the template argument.
Sorry for the previous answer.

On Friday, 26 February 2016 at 11:37:32 UTC, BBasile wrote:
> Erratum! Actually you can, example:
>
> import std.stdio;
>
> string foo(double a)()
> {
>     return "auto value = " ~ a.stringof ~ ";";
> }
>
> void main(string[] args)
> {
>     mixin(foo!0.1);
>     writeln(value); // 0.1
>     writeln(typeof(value).stringof); // double
> }
>
> So you have to use .stringof on the template argument.
> Sorry for the previous answer.

Thank you!