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digitalmars.D.learn - function-local template specialization error

reply canalpay <canalpayciftci gmail.com> writes:
void main()
{
    T input(T)()
    {}
 
    T input(T : string)()
    {}
}

Error message :

isimsiz.d(6): found 'input' when expecting ';' following statement
isimsiz.d(6): found ':' when expecting ')'
isimsiz.d(6): found 'string' when expecting ';' following statement
isimsiz.d(6): found ')' instead of statement
isimsiz.d(8): unrecognized declaration
 
Shouldn't that work?

And

void main()
{
    void input(T)()
    {}
 
    void input(T : string)()
    {}
}

Again, Shouldn't that work?

Error message:
isimsiz.d(6): Error: declaration input(T : string) is already defined

there is no problem when the templates are in the global namespace.
Jul 14 2010
parent reply bearophile <bearophileHUGS lycos.com> writes:
canalpay:
 void main()
 {
     T input(T)()
     {}
  
     T input(T : string)()
     {}
 }

In D2 you can't define templates inside functions. Bye, bearophile
Jul 14 2010
parent reply canalpay <canalpayciftci gmail.com> writes:
bearophile Wrote:
 In D2 you can't define templates inside functions.
 
 Bye,
 bearophile

Thanks, But this example works: void main() { T input(T)() {} } Why ?
Jul 14 2010
parent reply bearophile <bearophileHUGS lycos.com> writes:
canalpay:
 Thanks, But this example works:
 void main()
 {
     T input(T)()
     {}
 
 }
 
  Why ?

You are right. Beside allowing nested functions (this is well known), it seems D2 also accepts the definition (with template constraint too) and instantiation of simple templates inside functions, I didn't know this. But currently nested functions can't be overloaded. Probably for similar reasons inside a function you can't define more than one template with the same name. I presume this limit can be removed, so if you really need this you can ask for an enhancement request and if you can add a patch too to increase a bit the probability to see it fulfilled someday. Bye, bearophile
Jul 14 2010
parent Don <nospam nospam.com> writes:
bearophile wrote:
 canalpay:
 Thanks, But this example works:
 void main()
 {
     T input(T)()
     {}

 }

  Why ?

You are right. Beside allowing nested functions (this is well known), it seems D2 also accepts the definition (with template constraint too) and instantiation of simple templates inside functions, I didn't know this. But currently nested functions can't be overloaded. Probably for similar reasons inside a function you can't define more than one template with the same name. I presume this limit can be removed, so if you really need this you can ask for an enhancement request and if you can add a patch too to increase a bit the probability to see it fulfilled someday. Bye, bearophile

The spec explicitly says: "Unlike module level declarations, declarations within function scope are processed in order. This means that two nested functions cannot mutually call each other: [snip] Future directions: This restriction may be removed." My guess is that it will become possible eventually.
Jul 14 2010