Re: Cross product template
On Wed, 15 May 2013 03:31:40 +0200, Diggory wrote: I have a vector struct, Vector(T, uint N) templated on the type T and number of components, N. I'm trying to write a function "cross" which will calculate the cross product of a number of vectors. For a given number of components, N, the cross function should take N-1 arguments, each one a Vector!(?, N) and will return a vector perpendicular to the vectors passed in. The ? means the type is free to be anything. The problem is that however I try to write it, the template argument deduction isn't powerful enough to work out which instantiation to use. I thought something like this would work to deduce the parameters and then I could use constraints to enforce the other rules, but no: auto cross(T, N, U...)(Vector!(T, N) a, U b) { return 0; } auto cross(T, uint N, U...)(Vector!(T,N) a, U b) { return 0; } Oughta work. -- Simen
Re: Cross product template
On Wednesday, 15 May 2013 at 01:31:43 UTC, Diggory wrote: I have a vector struct, Vector(T, uint N) templated on the type T and number of components, N. I'm trying to write a function "cross" which will calculate the cross product of a number of vectors. For a given number of components, N, the cross function should take N-1 arguments, each one a Vector!(?, N) and will return a vector perpendicular to the vectors passed in. The ? means the type is free to be anything. The problem is that however I try to write it, the template argument deduction isn't powerful enough to work out which instantiation to use. I thought something like this would work to deduce the parameters and then I could use constraints to enforce the other rules, but no: auto cross(T, N, U...)(Vector!(T, N) a, U b) { return 0; } Well, after much trial and error I ended up with this, which seems to work: template VectorN(T : Vector!(T, N), uint N) { enum VectorN = N; } template isVectorN(uint N) { template isVectorN(T) { enum isVectorN = VectorN!(T) == N; } } auto cross(T...)(T args) if (allSatisfy!(isVectorN!(T.length+1), T) && T.length) { return 0; }
Cross product template
I have a vector struct, Vector(T, uint N) templated on the type T and number of components, N. I'm trying to write a function "cross" which will calculate the cross product of a number of vectors. For a given number of components, N, the cross function should take N-1 arguments, each one a Vector!(?, N) and will return a vector perpendicular to the vectors passed in. The ? means the type is free to be anything. The problem is that however I try to write it, the template argument deduction isn't powerful enough to work out which instantiation to use. I thought something like this would work to deduce the parameters and then I could use constraints to enforce the other rules, but no: auto cross(T, N, U...)(Vector!(T, N) a, U b) { return 0; }