January 27, 2019 Template constructor instantiation syntax remains unresolved | ||||
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I ran in to this bug from 2013 tonight: https://issues.dlang.org/show_bug.cgi?id=10689 Briefly, templated (and overloaded) constructor syntax is supported: this(int MAX_UNPACK = BCF_UN_ALL, T)(T *h, bcf1_t *b) if(is(T == VCFHeader) || is(T == bcf_hdr_t)) { ... } this(SS)(VCFHeader *vcfhdr, string chrom, int pos, string id, string _ref, string alt, float qual, SS filter, ) if (isSomeString!SS || is(SS == string[])) { ... } this(int MAX_UNPACK = BCF_UN_ALL)(VCFHeader *vcfhdr, string line) { ... } But there is no way (?) to instantiate these with specific template value parameters. (Deduction works just fine) auto rr = new VCFRecord!BCF_UN_STR(vw.vcfhdr, "..."); for example, returns the same error it did in 2013: Error: template instance `VCFRecord!BCF_UN_STR` VCFRecord is not a template declaration, it is a class Suggestions given in past threads include templating the class, but in this, and other posters' examples, the constructor is overloaded with several ways to construct the object. Too, I am not sure how templating the class would work with template value parameters (vice type params). Given that templating the constructor is well-supported syntactically, the suggestion to use a factory function seems inelegant. Thanks for listening and suggestions. James |
January 27, 2019 Re: Template constructor instantiation syntax remains unresolved | ||||
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Posted in reply to James Blachly | On Sunday, 27 January 2019 at 01:22:09 UTC, James Blachly wrote:
> I ran in to this bug from 2013 tonight:
>
> https://issues.dlang.org/show_bug.cgi?id=10689
>
> Briefly, templated (and overloaded) constructor syntax is supported:
>
> this(int MAX_UNPACK = BCF_UN_ALL, T)(T *h, bcf1_t *b)
> if(is(T == VCFHeader) || is(T == bcf_hdr_t))
> {
> ...
> }
> this(SS)(VCFHeader *vcfhdr, string chrom, int pos, string id, string _ref, string alt, float qual, SS filter, )
> if (isSomeString!SS || is(SS == string[]))
> {
> ...
> }
> this(int MAX_UNPACK = BCF_UN_ALL)(VCFHeader *vcfhdr, string line)
> {
> ...
> }
>
>
> But there is no way (?) to instantiate these with specific template value parameters. (Deduction works just fine)
>
> auto rr = new VCFRecord!BCF_UN_STR(vw.vcfhdr, "...");
>
> for example, returns the same error it did in 2013:
>
> Error: template instance `VCFRecord!BCF_UN_STR` VCFRecord is not a template declaration, it is a class
>
>
>
> Suggestions given in past threads include templating the class, but in this, and other posters' examples, the constructor is overloaded with several ways to construct the object. Too, I am not sure how templating the class would work with template value parameters (vice type params).
>
> Given that templating the constructor is well-supported syntactically, the suggestion to use a factory function seems inelegant.
>
> Thanks for listening and suggestions.
> James
This works fro the struct case:
struct A {
string s;
int n;
this( string s) { this.s = s; }
this( int k)( int n) { this.n = n - k; }
}
void main()
{
A a = void;
a.__ctor!3(42);
}
Not sure about the class case but you can probably concoct something similar.
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