  In this paper, we present Q# implementations for arbitrary single-variabled
fixed-point arithmetic operations for a gate-based quantum computer based on
lookup tables (LUTs). In general, this is an inefficent way of implementing a
function since the number of inputs can be large or even infinite. However, if
the input domain can be bounded and there can be some error tolerance in the
output (both of which are often the case in practical use-cases), the quantum
LUT implementation of certain quantum arithmetic functions can be more
efficient than their corresponding reversible arithmetic implementations. We
discuss the implementation of the LUT using Q\# and its approximation errors.
We then show examples of how to use the LUT to implement quantum arithmetic
functions and compare the resources required for the implementation with the
current state-of-the-art bespoke implementations of some commonly used
arithmetic functions. The implementation of the LUT is designed for use by
practitioners to use when implementing end-to-end quantum algorithms. In
addition, given its well-defined approximation errors, the LUT implementation
makes for a clear benchmark for evaluating the efficiency of bespoke quantum
arithmetic circuits .
