  Re-Pair is an efficient grammar compressor that operates by recursively
replacing high-frequency character pairs with new grammar symbols. The most
space-efficient linear-time algorithm computing Re-Pair uses
$(1+\epsilon)n+\sqrt n$ words on top of the re-writable text (of length $n$ and
stored in $n$ words), for any constant $\epsilon>0$; in practice however, this
solution uses complex sub-procedures preventing it from being practical. In
this paper, we present an implementation of the above-mentioned result making
use of more practical solutions; our tool further improves the working space to
$(1.5+\epsilon)n$ words (text included), for some small constant $\epsilon$. As
a second contribution, we focus on compact representations of the output
grammar. The lower bound for storing a grammar with $d$ rules is
$\log(d!)+2d\approx d\log d+0.557 d$ bits, and the most efficient encoding
algorithm in the literature uses at most $d\log d + 2d$ bits and runs in
$\mathcal O(d^{1.5})$ time. We describe a linear-time heuristic maximizing the
compressibility of the output Re-Pair grammar. On real datasets, our grammar
encoding uses---on average---only $2.8\%$ more bits than the
information-theoretic minimum. In half of the tested cases, our compressor
improves the output size of 7-Zip with maximum compression rate turned on.
