• james.p.leblanc (14/38) Aug 09 2021 Suppose "foo_double" should return a complex double slice, with
• H. S. Teoh (9/15) Aug 09 2021 Your syntax is wrong; the declaration should be:
• Paul Backus (12/28) Aug 09 2021 I think what you want is:
• james.p.leblanc (9/39) Aug 09 2021 H.S & Paul,

james.p.leblanc <james.p.leblanc gmail.com> writes:

Suppose "foo_double" should return a complex double slice, with 
double input args.
Similarly "foo_float" should return a float slice, with float 
input args.

I thought it should be easy to parameterize with a template 
taking a SINGLE
argument, either a"double" or "float" as follows:

import std.stdio;
import std.complex;

Complex!double[] foo_double(double x, double y){
   auto r = [x, x];
   auto i = [y, y];
   auto z = [ Complex!double(x, y), Complex!double(x,y) ];
   return z;
}

Complex!float[] foo_float(float x, float y){
   auto r = [x, x];
   auto i = [y, y];
   auto z = [ Complex!float(x, y), Complex!float(x,y) ];
   return z;
}

**T[] foo_temp(Complex!T[])(T x, T y){
   auto r = [x, x];
   auto i = [y, y];
   auto z = [ Complex!T(x, y), Complex!T(x,y) ];
   return z;
}**

void main(){
   auto yd = foo_double(1.1, 2.2);
   writeln(yd); ...
 }

But, no ... I am WRONG!  I get the message:

qqq.d(18): Error: identifier expected for template value parameter

Nested templates using Complex! really have me confused.  How 
should I
be thinking about such things in order to understand better?

Best Regards,
James

"H. S. Teoh" <hsteoh quickfur.ath.cx> writes:

On Mon, Aug 09, 2021 at 06:35:56PM +0000, james.p.leblanc via
Digitalmars-d-learn wrote:
[...]
 **T[] foo_temp(Complex!T[])(T x, T y){
   auto r = [x, x];
   auto i = [y, y];
   auto z = [ Complex!T(x, y), Complex!T(x,y) ];
   return z;
 }**


Your syntax is wrong; the declaration should be:

	Complex!T[] foo_temp(T)(T x, T y) { ... }

Basically, you're parametrizing on T, and returning an array of a
Complex type built upon T.


T

-- 
Curiosity kills the cat. Moral: don't be the cat.

Paul Backus <snarwin gmail.com> writes:

On Monday, 9 August 2021 at 18:35:56 UTC, james.p.leblanc wrote:
```d
T[] foo_temp(Complex!T[])(T x, T y){
   auto r = [x, x];
   auto i = [y, y];
   auto z = [ Complex!T(x, y), Complex!T(x,y) ];
   return z;
}
```

void main(){
   auto yd = foo_double(1.1, 2.2);
   writeln(yd); ...
 }

 But, no ... I am WRONG!  I get the message:

 qqq.d(18): Error: identifier expected for template value 
 parameter

I think what you want is:

```d
Complex!T[] foo_temp(T)(T x, T y) {
   auto r = [x, x];
   auto i = [y, y];
   auto z = [ Complex!T(x, y), Complex!T(x,y) ];
   return z;
}
```

This is what I get when I take one of the non-template versions 
and replace `float` or `double` with `T`.

james.p.leblanc <james.p.leblanc gmail.com> writes:

On Monday, 9 August 2021 at 18:44:34 UTC, Paul Backus wrote:
 On Monday, 9 August 2021 at 18:35:56 UTC, james.p.leblanc wrote:
```d
T[] foo_temp(Complex!T[])(T x, T y){
   auto r = [x, x];
   auto i = [y, y];
   auto z = [ Complex!T(x, y), Complex!T(x,y) ];
   return z;
}
```

void main(){
   auto yd = foo_double(1.1, 2.2);
   writeln(yd); ...
 }

 But, no ... I am WRONG!  I get the message:

 qqq.d(18): Error: identifier expected for template value 
 parameter

 I think what you want is:

 ```d
 Complex!T[] foo_temp(T)(T x, T y) {
   auto r = [x, x];
   auto i = [y, y];
   auto z = [ Complex!T(x, y), Complex!T(x,y) ];
   return z;
 }
 ```

 This is what I get when I take one of the non-template versions 
 and replace `float` or `double` with `T`.

H.S & Paul,

Wow, thanks for the quick replies!

It all seems so simple now ... but I just could not see it!

I had been completely (and confidently, unfortunately) 
misunderstanding
the syntax of that left most column.

Thanks again,
James