Add unary minus operator overloadings to mpq & mpfp

src/util/numerics/mpfp.h

@@ -448,6 +448,8 @@ public:
     mpfp & operator--() { return operator-=(1lu); }
     mpfp operator--(int) { mpfp r(*this); --(*this); return r; }
 
+    mpfp operator-() const { mpfp t = *this; t.neg(); return t; }
+
     void floor() { mpfr_floor(m_val, m_val); }
     void ceil () { mpfr_ceil (m_val, m_val); }
     void round() { mpfr_round(m_val, m_val); }

src/util/numerics/mpq.h

@@ -178,6 +178,8 @@ public:
     mpq & operator--() { return operator-=(1); }
     mpq operator--(int) { mpq r(*this); --(*this); return r; }
 
+    mpq operator-() const { mpq t = *this; t.neg(); return t; }
+
     // a <- numerator(b)
     friend void numerator(mpz & a, mpq const & b) { mpz_set(zval(a), mpq_numref(b.m_val)); }
     // a <- denominator(b)