12.3 C++ Interface Rationals

In all the following constructors, if a fraction is given then it should be in canonical form, or if not then mpq_class::canonicalize called.

Function: mpq_class::mpq_class (type op)

Function: mpq_class::mpq_class (integer num, integer den)

Construct an mpq_class. The initial value can be a single value of any type (conversion from mpf_class is explicit), or a pair of integers (mpz_class or standard C++ integer types) representing a fraction, except that long long and long double are not supported. For example,

mpq_class q (99);
mpq_class q (1.75);
mpq_class q (1, 3);

Function: explicit mpq_class::mpq_class (const mpq_t q)

Construct an mpq_class from an mpq_t. The value in q is copied into the new mpq_class, there won’t be any permanent association between it and q.

Function: explicit mpq_class::mpq_class (const char *s, int base = 0)

Function: explicit mpq_class::mpq_class (const string& s, int base = 0)

Construct an mpq_class converted from a string using mpq_set_str (see Initializing Rationals).

If the string is not a valid rational, an std::invalid_argument exception is thrown. The same applies to operator=.

Function: mpq_class operator"" _mpq (const char *str)

With C++11 compilers, integral rationals can be constructed with the syntax 123_mpq which is equivalent to mpq_class(123_mpz). Other rationals can be built as -1_mpq/2 or 0xb_mpq/123456_mpz.

Function: void mpq_class::canonicalize ()

Put an mpq_class into canonical form, as per Rational Number Functions. All arithmetic operators require their operands in canonical form, and will return results in canonical form.

Function: mpq_class abs (mpq_class op)

Function: int cmp (mpq_class op1, type op2)

Function: int cmp (type op1, mpq_class op2)

Function: double mpq_class::get_d (void)

Function: string mpq_class::get_str (int base = 10)

Function: int mpq_class::set_str (const char *str, int base)

Function: int mpq_class::set_str (const string& str, int base)

Function: int sgn (mpq_class op)

Function: void mpq_class::swap (mpq_class& op)

Function: void swap (mpq_class& op1, mpq_class& op2)

These functions provide a C++ class interface to the corresponding GMP C routines.

cmp can be used with any of the classes or the standard C++ types, except long long and long double.

Function: mpz_class& mpq_class::get_num ()

Function: mpz_class& mpq_class::get_den ()

Get a reference to an mpz_class which is the numerator or denominator of an mpq_class. This can be used both for read and write access. If the object returned is modified, it modifies the original mpq_class.

If direct manipulation might produce a non-canonical value, then mpq_class::canonicalize must be called before further operations.

Function: mpz_t mpq_class::get_num_mpz_t ()

Function: mpz_t mpq_class::get_den_mpz_t ()

Get a reference to the underlying mpz_t numerator or denominator of an mpq_class. This can be passed to C functions expecting an mpz_t. Any modifications made to the mpz_t will modify the original mpq_class.

If direct manipulation might produce a non-canonical value, then mpq_class::canonicalize must be called before further operations.

Function: istream& operator>> (istream& stream, mpq_class& rop);

Read rop from stream, using its ios formatting settings, the same as mpq_t operator>> (see C++ Formatted Input).

If the rop read might not be in canonical form then mpq_class::canonicalize must be called.