## digitalmars.D - Passing Tuple Arguments to Tuple

• Xinok (25/25) Dec 24 2006 I was experimenting with recursive templates. I successfully created a
• BCS (10/39) Dec 24 2006 I haven't actually played around with your code but this looks like a
• Xinok (9/9) Dec 26 2006 I found out it's a problem with using an index []
• Kirk McDonald (8/19) Dec 26 2006 Yes, this is a known issue. See bugs 582 and 586:
Xinok <xnknet gmail.com> writes:
```I was experimenting with recursive templates. I successfully created a
template which could test if a value is prime or not. What I tried to do next
is create another template which would use a tuple to build a list of primes.

template IsPrime(uint V, uint M = 2){
static if(V == 0 || V == 1) const bool IsPrime = false;
else static if(M*M <= V){
static if(V%M == 0) const bool IsPrime = false;
else const bool IsPrime = IsPrime!(V, M+1);
}
else const bool IsPrime = true;
}

template FindPrime(V...){
static if(V[0] < 2){
alias V[1..length] FindPrime;
}
static if(IsPrime!(V[0])){
alias FindPrime!(V[0]-1, V[0..length]) FindPrime; // Error: 'tuple V is used
as a type'
}
else{
alias FindPrime!(V[0]-1, V[1..length]) FindPrime;
}
}

This error makes no sense to me. What's the problem? Why can't you pass tuples
to tuples?
```
Dec 24 2006
```Xinok wrote:
I was experimenting with recursive templates. I successfully created a
template which could test if a value is prime or not. What I tried to do next
is create another template which would use a tuple to build a list of primes.

template IsPrime(uint V, uint M = 2){
static if(V == 0 || V == 1) const bool IsPrime = false;
else static if(M*M <= V){
static if(V%M == 0) const bool IsPrime = false;
else const bool IsPrime = IsPrime!(V, M+1);
}
else const bool IsPrime = true;
}

template FindPrime(V...){
static if(V[0] < 2){
alias V[1..length] FindPrime;
}
static if(IsPrime!(V[0])){
alias FindPrime!(V[0]-1, V[0..length]) FindPrime; // Error: 'tuple V is used
as a type'
}
else{
alias FindPrime!(V[0]-1, V[1..length]) FindPrime;
}
}

This error makes no sense to me. What's the problem? Why can't you pass tuples
to tuples?

I haven't actually played around with your code but this looks like a
bug[1] I keep running into. try this

static if(IsPrime!(V[0])){
const uint abc = V[0]; ///<<<<<<<
alias FindPrime!(abc-1, V[0..length]) FindPrime; 			}

it messes up implicit proposes but it often makes things work. OTOH a
cast might do the trick but I haven tried that.

[1] I think this is a bug (see my posts in digitalmars.d.announce about
"spirit in 100 LOC") but I'm, not sure it tectonically is incorrect.
```
Dec 24 2006
Xinok <xnknet gmail.com> writes:
```I found out it's a problem with using an index []

template a(V...){
alias V a;
}

template b(V...){
alias a!(V) b; // This compiles OK
// alias a!(V[0]) b; // But this gives the error
// alias a!(V[0..length]) b; // And so does this
}
```
Dec 26 2006
Kirk McDonald <kirklin.mcdonald gmail.com> writes:
```Xinok wrote:
I found out it's a problem with using an index []

template a(V...){
alias V a;
}

template b(V...){
alias a!(V) b; // This compiles OK
// alias a!(V[0]) b; // But this gives the error
// alias a!(V[0..length]) b; // And so does this
}

Yes, this is a known issue. See bugs 582 and 586:

http://d.puremagic.com/issues/show_bug.cgi?id=582
http://d.puremagic.com/issues/show_bug.cgi?id=586

--
Kirk McDonald
Pyd: Wrapping Python with D
http://pyd.dsource.org
```
Dec 26 2006