# Algebra definitions¶

The main algebra classes for Acts are defined in the Acts/Definitions/Algebra.hpp header file. The basic scalar type can be defined via this file and is set per default to double, however, if ACTS_CUSTOM_SCALAR is set it will be used instead.

#ifdef ACTS_CUSTOM_SCALAR
using ActsScalar = ACTS_CUSTOM_SCALAR;
#else
using ActsScalar = double;
#endif


It is recommended within the code to deduce the Scalar type from the Event Data object, e.g.

Currently only the Core package builds with float precision.