This identifier permits to construct an object embedding a compile-time integer N.

Template Parameters

N	the compile-time integer value

It is typically used in conjunction with the Eigen::seq and Eigen::seqN functions to pass compile-time values to them:

seqN(10,fix<4>,fix<-3>)   // <=> [10 7 4 1]

See also the function fix(int) to pass both a compile-time and runtime value.

In c++14, it is implemented as:

template<int N> static const internal::FixedInt<N> fix{};

where internal::FixedInt<N> is an internal template class similar to std::integral_constant <int,N> Here, fix<N> is thus an object of type internal::FixedInt<N>.

In c++98/11, it is implemented as a function:

template<int N> inline internal::FixedInt<N> fix();

Here internal::FixedInt<N> is thus a pointer to function.

If for some reason you want a true object in c++98 then you can write:

fix<N>() 

which is also valid in c++14.

See also

fix<N>(int), seq, seqN

This function returns an object embedding both a compile-time integer N, and a fallback runtime value val.

Template Parameters

N	the compile-time integer value

Parameters

val	the fallback runtime integer value

This function is a more general version of the fix identifier/function that can be used in template code where the compile-time value could turn out to actually mean "undefined at compile-time". For positive integers such as a size or a dimension, this case is identified by Eigen::Dynamic, whereas runtime signed integers (e.g., an increment/stride) are identified as Eigen::DynamicIndex. In such a case, the runtime value val will be used as a fallback.

A typical use case would be:

template<typename Derived> void foo(const MatrixBase<Derived> &mat) {
  const int N = Derived::RowsAtCompileTime==Dynamic ? Dynamic : Derived::RowsAtCompileTime/2;
  const int n = mat.rows()/2;
  ... mat( seqN(0,fix<N>(n) ) ...;
}

In this example, the function Eigen::seqN knows that the second argument is expected to be a size. If the passed compile-time value N equals Eigen::Dynamic, then the proxy object returned by fix will be dissmissed, and converted to an Eigen::Index of value n. Otherwise, the runtime-value n will be dissmissed, and the returned ArithmeticSequence will be of the exact same type as seqN(0,fix<N>) .

See also

fix, seqN, class ArithmeticSequence

Can be used as a parameter to DenseBase::operator()(const RowIndices&, const ColIndices&) to index all rows or columns

Can be used as a parameter to Eigen::seq and Eigen::seqN functions to symbolically reference the last element/row/columns of the underlying vector or matrix once passed to DenseBase::operator()(const RowIndices&, const ColIndices&).

This symbolic placeholder supports standard arithmetic operations.

A typical usage example would be:

using namespace Eigen;
using Eigen::last;
VectorXd v(n);
v(seq(2,last-2)).setOnes();

See also

end

Can be used as a parameter to Eigen::seq and Eigen::seqN functions to symbolically reference the last+1 element/row/columns of the underlying vector or matrix once passed to DenseBase::operator()(const RowIndices&, const ColIndices&).

This symbolic placeholder supports standard arithmetic operations. It is essentially an alias to last+fix<1>.

See also

last