digitalmars.D.learn - How do I specify a variadic template constraint on all the whole
- Atila Neves (19/19) Jul 18 2013 http://stackoverflow.com/questions/17724479/in-d-how-do-i-specify-a-vari...
- Andrej Mitrovic (27/32) Jul 18 2013 Here you go:
- Atila Neves (8/41) Jul 18 2013 Thanks! I had to change allSatistfy!(isSomeString, Symbols) to
http://stackoverflow.com/questions/17724479/in-d-how-do-i-specify-a-variadic-template-constraint-on-all-the-whole-tuple Posted on stackoverflow first since I think it's better for the language to get traction there. For completeness sake, posting the text of the question here as well: I'm writing 2 overloads of a function, both of them with variadic template compile-time parameters. One should take symbols as the templates, the other strings. I want to constrain the template instantiation to these two cases. The best I came up with was this: bool func(SYMBOLS...)() if(!is(typeof(SYMBOLS[0]) == string)) { } and bool func(STRINGS...)() if(is(typeof(STRINGS[0]) == string)) { } Obviously this only checks the first template parameter, and while it works given the code I've written so far, I wish I could say "only for all strings" and "only for not all strings". Is there a way? Thanks in advance.
Jul 18 2013
On Thursday, 18 July 2013 at 13:18:29 UTC, Atila Neves wrote:bool func(SYMBOLS...)() if(!is(typeof(SYMBOLS[0]) == string)) { } and bool func(STRINGS...)() if(is(typeof(STRINGS[0]) == string)) { }Here you go: ----- import std.string; import std.traits; import std.typetuple; import std.functional; bool func(Symbols...)(Symbols symbols) if (!anySatisfy!(isSomeString, Symbols)) { return true; } bool func(Strings...)(Strings strings) if (allSatisfy!(isSomeString, Strings)) { return true; } void main() { func("1", "2"); func(1, 2); static assert(!__traits(compiles, func(1, "2"))); } ----- And remember you have to actually list the runtime arguments after the type arguments (e.g. 'Strings strings'), otherwise the template won't match.
Jul 18 2013
Thanks! I had to change allSatistfy!(isSomeString, Symbols) to allSatistfy!(isSomeString, typeof(Symbols)) but it works. I don't use the same types as runtimne arguments actually. You might see why if/when I finish this particular project and announce it. Shall I answer my own question on stackoverflow? Atila On Thursday, 18 July 2013 at 13:25:55 UTC, Andrej Mitrovic wrote:On Thursday, 18 July 2013 at 13:18:29 UTC, Atila Neves wrote:bool func(SYMBOLS...)() if(!is(typeof(SYMBOLS[0]) == string)) { } and bool func(STRINGS...)() if(is(typeof(STRINGS[0]) == string)) { }Here you go: ----- import std.string; import std.traits; import std.typetuple; import std.functional; bool func(Symbols...)(Symbols symbols) if (!anySatisfy!(isSomeString, Symbols)) { return true; } bool func(Strings...)(Strings strings) if (allSatisfy!(isSomeString, Strings)) { return true; } void main() { func("1", "2"); func(1, 2); static assert(!__traits(compiles, func(1, "2"))); } ----- And remember you have to actually list the runtime arguments after the type arguments (e.g. 'Strings strings'), otherwise the template won't match.
Jul 18 2013