[linux, ubuntu] personal D module not found in the same directory

[le TeXnicien de surface]

hello all

I'm begining to learn to program with D.

I've made this tiny module written in file truc.d
<module>
module truc;

double carre(double x){
     return x*x;
}
</module>

and this tiny program written in file jeteste.d

<prgm>
import truc;  // I've also tried import T = truc;
import std.stdio;

double cube(double x){
     return x*x*x;
}

void main(){
     double y = 5;
     auto z = carre(y);
     // alt version :
     // auto z = T.carre(y);
     writeln("vu ici ",z);
}
</prgm>

Both files are in the same directory.

I run dmd jeteste.d in the said directory

and I obtain this message:

jeteste.o: In function `_Dmain':
jeteste.d:(.text._Dmain+0x1e): undefined reference to
`_D4truc5carreFdZd'
collect2: ld a retourné 1 code d'état d'exécution
--- errorlevel 1

where do I err?

any hint would be greatly appreciated

many thanks in advance