  We describe a new C++ library for multiprecision arithmetic for numbers in
the order of 100--500 bits, i.e., representable with just a few limbs. The
library is written in "optimizing-compiler-friendly" C++, with an emphasis on
the use of fixed-size arrays and particular function-argument-passing styles
(including the avoidance of naked pointers) to allow the limbs to be allocated
on the stack or even in registers. Depending on the particular functionality,
we get close to, or significantly beat the performance of existing libraries
for multiprecision arithmetic that employ hand-optimized assembly code.
  Most functions in the library are constant-time, which is a necessity for
secure implementations of cryptographic protocols.
  Beyond the favorable runtime performance, our library is, to the best of the
author's knowledge, the first library that offers big-integer computations
during compile-time. For example, when implementing finite-field arithmetic
with a fixed modulus, this feature enables the automatic precomputation (at
compile time) of the special modulus-dependent constants required for Barrett
and Montgomery reduction. Another application is to parse (at compile-time) a
base-10-encoded big-integer literal.
